Histology 2nd Semester D.A.T.W
Histology 2nd Semester 1
© D. Werner
HISTOLOGY EXAM REVIEW SCRIPT – 2ND SEMESTER
Histology 2nd Semester D.A.T.W
2
2nd week: Lymphatic tissues (NOTE: I did not include the lectures in here which are downloadable -> some knowledge is more detailed here or additional) • •
•
•
Sites where Lymphocytes proliferate, differentiate and mature Lymphatic organs o Encapsulated Lymph Node Thymus Spleen o Epithelium Associated Lymphoid Tissue (NOT encapsulated) Loose lymphatic tissues -> lymphatic follicles -> e.g. tonsils Bone Marrow Gut Associated Lymphatic Tissue (GALT) Mucosa Associated Lymphatic Tissue (MALT) Lymphatic Vessels o Start as tiny capillaries in loose connective tissue o Walls are more permeable then those of blood capillaries o -> large molecules (-> pathogens) enter here more easily then into the blood stream o Contain lymph -> clear liquid containing Lymphocytes/Macrophages, Tissue Debris, Pathogens Dendritic Cells (Not mentioned in Lecture but important) o Bone marrow derived Antigen Presenting Cell (APC) o Phagocytose foreign particles and present antigens to T-cells via MHC II molecules o Very effective APCs -> express high levels of MHC II AND co stimulatory molecules for T-cell activation o Dendritic Cells are found in the deep cortex of the lymph node
Histology 2nd Semester D.A.T.W
QUESTION 1 – PALATINE TONSIL (HE)
Part I – Histological Appearance •
• • • •
(1) Surface: Stratified Non-Keratinizing Squamous Epithelium (Since located in cavity opening -> Oral -> its not lined by pseudostratified ep.) (2) Deep crypt Lymphocytes (beneath epithelium) (3) Germinative Center (with surrounding Corona) Reticular Connective Tissue
Part II – Theory • • •
Tonsils are diffuse lymphatic tissue masses surrounded by an epithelial layer -> THEY ARE NOT ENCAPSULATED Guard the body against pathogenic substances -> are a site of initial immune response In the Facial region a special ring of tonsils is protecting the “gates to the outside of the body” -> WALDEYER`s Tonsillar ring o Lingual Tonsils (Location: Root of Tongue) -> stratified non-k squamous epithelium; lots of glands; muscles on the slide are seen in all 3 directions (tongue) o Palatine Tonsils (Location: Soft Palate inbetween palatoglossal and palatopharyngeal arches) -> stratified non-k squamous epithelium; some glands; muscles in 2 directions (palatopharyngeus, palatoglossus) Special for Palatine Tonsil: Contains deep crypt in which bacteria can settle down and “hide” -> follicular tonsillitis; Tissue debris and pus collecting in the crypts appears as white spots on the surface of the tonsil
3
Histology 2nd Semester D.A.T.W o Tubal Tonsils (Location: Behind the cartilage of the auditory tube in the pharynx) -> pseudostratified non-k columnar epithelium with kinocilia; !! Special: in this slide you can find cartilage from the auditory tube !! o Pharyngeal Tonsils (Location: Fornix of Pharynx) -> same as Tubal; 4 Special for Pharyngeal Tonsils: during childhood they can swell and block the nasopharyngeal opening -> nasal breathing impossible; Tumors occur frequently • All kinds of lymphatic tissues contain lymphatic follicles or nodules (not to mix with nodes) -> accumulations of B-Lymphocytes. Those follicles can contain “germinative centers” which appear upon initiation of immune response -> accumulation of differentiating B-cells. They are stained less because of less dense Nuclei (Euchromatin, because cell is active -> lesse dense coiling of DNA). Germinal Centers are surrounded by the corona -> outer ring of matured B-lymphocytes There are TWO kinds of follicles: 1) Primary Follicles -> contain mainly small lymphocytes 2) Secondary Follicles -> make up the majority -> contain the germinal centers • Once a lymphocyte encounters an antigen it returns to a primary nodule and starts proliferation -> creation of 2ndary follicle • • •
•
In the spaces not occupied by B-cell follicles (not good distinguishable on the Tonsil slides) -> T-Lymphocytes are residing In some parts lymphocytes have been incorporated into the epithelial layer -> at those regions they basal layer is disrupted Reticular Connective Tissue forms the “skeleton” of all lymphatic tissues o Collagen Type III o Stainable by PAS (rich in carbohydrates) or AgNO3 In the Connective Tissue High Endothelial Veins (HEVs) might be visuable -> these are venules which have a special endothelium -> Lymphocytes are able to cross this layer to enter the Tonsil (possible in all Lymphatic organs) from the bloodstream
Histology 2nd Semester D.A.T.W
5 2nd slide Palatine Tonsil • • • •
Higher Magnification (1) Stratified squamous non keratinized epithelium (2) Excretory duct (3) Mixed salivary gland
Histology 2nd Semester D.A.T.W
Question 2 – Lymph Node (HE)
6
Part I – Histological Appearance • • • • • •
• •
•
• Important: • Not visible here but in other lymph organ slides you find lymphatic vessels (or sinuses) in cross or tangential section -> these contain eosinophilic homogenous fluid -> lymph • In case it’s a relative big section it is the vas efferens close to the hilum • Due to the histological methods -> RBCs can “slide” in the lymph vessels but THEY ARE NOT THERE in real life!
•
Bean shaped organ (not always visible due to layer sectioning) Convex Back Part Concave Front Part -> containing (7) “hilus” (1) Capsule (Dense Connective Tissue) (2) Marginal Sinus (Containing Lymph) (3) Trabeculae (invaginations of the dense connective tissue towards the inner part > forming C.T. septa (3) Trabecular sinus (Containing Lymph) (4) Superficial Cortex (or Nodular Cortex) o Follicles -> B-Cells o Germinative Centers o Lymphatic sinuses (5) Deep Cortex (or Paracortex) o No nodules here o T-Cells (6) Medulla o Lymphatic tissue cords (made up by lining of lymphocytes) NOT visible or distinguishable o Macrophages o Dendritic cells o Plasma cells o Reticular framework
Histology 2nd Semester D.A.T.W Histological appearance II • • • • • • • • •
(1) Trabecula (1) Trabecula sinus (2) Germinal center (3) Cortex (4) Paracortex (5) Marginal sinus (6) Medulla (7) Medullary sinus (8) Medullary cords
7
Histology 2nd Semester D.A.T.W Part II – Theory • • • • •
•
Lymph nodes are small, bean shaped, encapsulated lymphatic organs Size: 1mm – 2cm Contains all Phagocytotic cells + Lymphocytes (undifferentiated and differentiated) Skeleton formed by Reticular Meshwork (Collagen Type III, Reticular cell processes wrapped around secreted fibers for stabilization) Lymphatic Circulation: o Afferent vessels Carry lymph towards the node Enter at convex back Smaller then big efferent vessel o Efferent vessels Carry lymph away from the node Leave at hilum -> depression on concave surface -> also blood vessels enter and leave here (see below) o 90% of Lymphocytes enter the node by blood circulation -> blood vessels enter at hilum -> Highly Endothelial Veins act as gates o HEVs are also creating a sucking effect (I mean in the sense of negative pressure creation ☺) -> contain high amount of aquaporins -> high amount of fluid transported to hilum by afferent lymph vesseks is absorbed immediately -> pulling entering particles (and so lymphocytes) into the deep cortex) [this is written on page 419 in ROSS 5th edition] o HEVs contain receptors for lymphocytes which encountered an antigen -> signal them to leave the vessel and enter the node o The movement across the epithelial wall: “diapedesis” They serve as filters in the network of lymph vessels -> once lymph is passing through a node -> foreign substance will be trapped in reticular meshwork -> processing by cells of immune system o Lymphatic fluid is circulating inside the lymphatic sinuses o -> those sinuses are not clean, open spaces such as blood vessels -> filled with processes of macrophages, recticular cells + reticular fibers o -> ! even if macrophages are not residing within the sinus -> their processes are monitoring the area like touch sensors! o The sinuses have continuous epithelial lining when facing connective tissue but are discontinuous when facing the parenchymal part of lymphatic organ o Flow of lymph from outside to Inside: 1st -> Afferent Vessel 2nd -> Marginal Sinus 3rd -> Trabecula sinus -> draining towards inside 4th -> Medullary sinus 5th -> Efferent vessel at hilum
8
Histology 2nd Semester D.A.T.W •
•
Morphology of a Plasma cell o Large cell o Nucleus contains spokelike structures Lymph Nodes enlarge when lymphocytes are responding to an antigen -> often palpable
9
Histology 2nd Semester D.A.T.W
Question 3 – Spleen HE Part I Histological Appearance • • • • • • • •
(1) Dense C.T. Capsule (2) White Pulp (3) Trabeculae (extend from capsule) (4) PALS (5) Splenic follicle (6) Central Artery (7) Marginal Zone (8) Venous Sinus
10
Histology 2nd Semester D.A.T.W Part II – Theory • • • •
• • •
•
Largest lymphatic organ Located in upper left quadrant of abdominal cavity -> rich blood supply Morphologic + Immunologic filtering functions (see end of chapter) Surrounded by dense C.T. capsule o From the capsule Trabeculae (as in Tonsils) extend into parenchyma o The C.T. of the capsule contains myofibroblasts -> contractile elements -> contraction helps to discharge stored RBCs in systemic circulation Hilum (as in lymph node) -> located on medial side, serves as entry point for splenic artery and vein, + nerves and lymphatic vessels Lymphatic vessels inside originate in the white pulp (see below) and are a route for lymphocytes leaving the spleen White Pulp o Appears basophilic in HE staining -> due to heterochromatin of lymphocytes o Mostly lymphocytes (B and T) o Contains a branch of the splenic artery –> Central Artery sends branches to the white pulp sends branches to the splenic sinuses at the perimeter of the white pulp -> “marginal sinuses” o Lymphocytes aggregate around this artery forming the Periarterial Lymphatic Sheath (PALS) o -> PALS Appears circular in cross section (can look like a lymphatic nodule -> but presence of central artery allows to distinguish) Contains T-lymphocytes -> can also be called “Thymus Dependend Zone” o Lymphatic Nodules can be found in the white pulp as extensions of the PALS Contain B-lymphocytes (same rules apply as in other lymphatic tissues) Contain germinal centers In the spleen the nodules can become very big (visible to naked eye) -> these enlarged nodules are “splenic nodules” OR “malphigian corpuscles” Red Pulp (main role -> blood filtration o Red appearance due to large number of RBCs o Consists of splenic sinuses separated by splenic cords Splenic sinuses • Special sinusoidal vessels lined by rod-shaped endothelial cells • Few contact points between adjacent endothelial cells -> high level of fenestration • -> Blood cells can pass in and out
11
Histology 2nd Semester D.A.T.W
• •
• Macrophage processes extend into the sinuses for blood monitoring • Sinuses do NOT possess a continuous basal lamina • Orientation of the basal lamina I didn’t understand • No pericytes present in wall of splenic sinuses • No smooth muscle present either Splenic cords • Meshwork of reticular fibers surrounded by processes of reticular cells • -> contains high amount of RBCs, Macrophages, Lymphocytes, Dendritic Cells, Plasma Cells, Granulocytes • Splenic macrophages Phagocytose damaged RBCs -> iron is recycled (breakdown of Hemoglobin is also initiated by splenic macrophages o Central artery sends (after branching off in white pulp -> look above) continues into red pulp -> branches into several straight arterioles called “penicillar arterioles” -> continue as capillaries -> some capillaries are surrounded by macrophages -> “sheathed capillaries” -> those empty directly into the reticular meshwork and are not further connected to splenic sinuses -> blood which enters that way into the splenic cords is exposed to macrophages and screened -> after it enters circulation again by squeezing through walls of splenic sinuses -> THIS IS CALLED “OPEN CIRCULATION” Blood collected in splenic sinuses drains into trabecular vein via branches of it -> then into larger veins -> finally leaves the spleen by the splenic vein through the hilum The spleen has both immune and hemopoietic functions (as mentioned at beginning) o Immune functions Antigen presentation -> initiation of immune response (white pulp) Activation and Proliferation of B, T-lymphocytes (white pulp) Production of Antibodies by Plasma cells (white pulp) Removal of MACROMOLECULAR antigens from blood (red pulp) o Hemopoietic functions (all taking place in red pulp) Retrieval of iron from destroyed RBCs -> stored in ferritin or hemosiderin Conversion of Heme to Bilirubin Formation of RBCs during early fetal life! Storage of blood in some species
12
Histology 2nd Semester D.A.T.W
•
Removal and destruction of abnormal or old RBCs and Thrombocytes • Macrophages recognize old or abnormal blood cells by several mechanisms o Nonspecific mechanisms -> involve morphologic and biochemical changes occurring in aged RBCs -> more rigid and become more easily trapped in meshwork of red pulp o Specific mechanisms involve antibodies against surface proteins of RBCs Despite all those functions the spleen is NOT ESSENTIAL FOR HUMAN LIFE -> it can be removed surgically (e.g. after trauma which causes bleeding from the spleen) -> as a consequence then the destruction and removal of old RBCs occurs in bone marrow and liver
13
Histology 2nd Semester D.A.T.W
Spleen Picture II • • • •
(1) PALS (2) Central Artery (3) B-Lymphocytes -> white pulp extension (4) Red Pulp
14
Histology 2nd Semester D.A.T.W
Question 5 – The Thymus HE Part I Histological Appearance • • • • • •
(1) Dense Connective Tissue Capsule (2) Trabeculae -> divide parenchyma into smaller lobules (contain blood + efferent lymph vessels) (3) Lobule (4) Thymic Medulla (5) Lobe (7) Hassal´s Corpuscles
15
Histology 2nd Semester D.A.T.W
Thymus 2nd picture • •
(1) Hassal`s body (2) Blood vessel
16
Histology 2nd Semester D.A.T.W Thymus 3rd picture • •
(1) Hassal`s Corpuscle (2) Keratohyalin granules
17
Part II - Theory • • • • •
• •
•
Histology 2nd Semester D.A.T.W
Thymus is 3rd (last) encapsulated lymphatic organ Its lumen is divided into smaller lobules by connective tissue septa -> trabeculae (these contain blood- and efferent lymph vessels BUT no afferent lymph 18 vessels The outer portion is formed by densely packed developing T-lymphocytes (Thymic Cortex) -> stained basophilic The inner portion is formed by the medulla which contains lower amounts of lymphocytes -> final sorting out takes place here as well as migration of mature t-cells into the blood vessels The basic meshwork is formed by epithelioreticular cells (NOT reticular cells -> there are no reticular fibers present) o -> these cells form a framework for the developing T-cells by extension of the cytoplasmic processes o -> exhibit features of epithelial (intercellular junctions, intermediate filaments) AND reticular cells o -> there is six different types of epithelioreticular cells, each one with specific characteristics but obviously they are not important for the exam o -> just know that they secrete Thymosine which assists in the development of T-cells The Thymus is the location for Thymic Education of T-Cells -> therefore you find NO Lymphatic Nodules containing B-lymphocytes During Life the Thymus goes through the phases o 1 - Epithelial Thymus o 2 – Lymphatic Stage Development of immune system is initiated after delivery and lasts till puberty -> in case of autoimmune disorders the thymus can be removed to prevent fatal consequences o 3 – Adipose Thymus At the end of puberty the Thymus becomes less active and its “active mass” is reduced -> biggest remainder is adipose tissue Development of T-Lymphocytes (Thymic Education) o During fetal life the Thymus contains multipotential lymphoid stem cells (originating from bone marrow) o -> their differentiation into T-cells is based on the expression/deletion of CD surface antigens o The development takes place in three stages 1 – (double negative stage) CD2 and CD7 are expressed on surface 2 – (middle stage) CD 1 is expressed 3 – (double positive stage) CD4, CD8 and others are expressed o -> NOW cells are confronted with self and foreign antigens by epithelioreticular cells -> if they recognize both they survive (POSITIVE SELECTION) -> otherwise they die and are phagocytosed o -> T-cells which survived now migrate from the cortex to the medulla o -> NOW cells are confronted with self antigens presented by own MHC molecules -> if they react to the own antigens they are sorted out (NEGATIVE SELECTION) -> this is important, otherwise the T-cells would attack the own body antigens
Histology 2nd Semester D.A.T.W Theory continuation •
19 Blood – Thymus barrier o In order for T-cells to develop under controlled conditions and to prevent early reaction with antigens -> NO antigens must enter Thymus uncontrolled o -> Thymal Cortex is sealed off by blood – Thymus barrier o This barrier has four security systems (from blood vessel lumen towards thymus) 1 – Endothelial lining of blood vessel lumen 2 – Basement membrane of the blood vessel 3 – Macrophages located in the connective tissue of the blood vessel wall (tunica adventitia) -> phagocytose any antigen which might have sneaked through 4 – Basement membrane of epithelioreticular cells lining thymic cortex 5 – epithelioreticular cells of thymic cortex
3rd week: Respiratory tract •
• •
Histology 2nd Semester D.A.T.W
The respiratory tract is formed by 20 o Nasal Cavity o Larynx o Trachea o Bronchus Tree o Intrapulmonary Bronchi The Basic Skeleton of respiratory organs is given by hyaline cartilage (at some points its missing) Lining of the respiratory organs -> There is a general order and kind of epithelium/mucosa with certain exceptions depending on each organ o General Lining Layer 1 -> EPITHELIUM Epithelium: pseudostratified – non-keratinizing – columnar epithelium with kinocilia (you can see basal bodies) -> containing mucous/goblet cells (these are NOT stained in HE slides but can be seen because at their position is an empty spot -> epithelium seems to be interrupted) -> basal cells -> line of reserve cells close to basal lamina -> form distinct row of nuclei which are close to each other The kinocilia are important for a sweeping motion which moves mucous from deepest parts of lungs towards the pharynx -> clearing out of foreign substances -> in smokers less kinocilia are present -> coughing o General Lining Layer 2 -> BASEMENT MEMBRANE Dense C.T. with high amount of collagen fibers Its underlying the basal lamina of the epithelial cells In smokers it can be thicker due to the irritation of the underlying mucosa o General Lining Layer 3 -> MUCOSA (OR LAMINA PROPRIA) Thick layer of loose C.T. Underlying the basement membrane Contains • Lymphocytes • Fibroblast • Eosinophil Granulocytes -> in this layer diffuse and follicular lymphatic tissue is present (see chapter one) which protects the airways -> depending on its position and the respiratory organ we differentiate between • MALT (Mucosa Associated Lymphatic Tissue) • BALT (Bronchus Associated Lymphatic Tissue)
Histology 2nd Semester D.A.T.W Theory Continuation • o General Lining Layer 4 -> SUBMUCOSA Underlying the mucosa -> the border between the two is formed by a distinct band of elastic fibers (elastic membrane) -> (! Those fibers are stained by orcein so you cannot see a distinct border between mucosa and submucosa in the HE slides!) Made up by loose C.T. containing • Distributing blood and lymphatic vessels • Mucous Glands The border of the submucosa is the beginning of fibers of the perichondrium
21
Histology 2nd Semester D.A.T.W
Question 6 – Larynx HE Part I – Histological Appearance • • • • • • • • • • • • •
(1) Vestibular fold (false vocal fold) (2) Vocal fold (3) Vocalis muscle (skeletal muscle) (4) Thyroid cartilage (hyaline cartilage) (5) Perichondrium (6) Respiratory epithelium (pseudostratified columnar epithelium with kinocilia (7) Special epithelium of vocal fold (stratified squamous non-keratinizing epithelium) (8) White fat cells (9) Thyroid gland (organ) (10) Mixed salivary glands (11) Vestibular fold (12) Conus elasticus (13) Ventricle of larynx
22
Histology 2nd Semester D.A.T.W
Larynx 2nd Picture • • • • • • • • •
(1) Vocal fold (2) Conus elasticus (3) Vocalis muscle (4) Mucous alveoli (5) Serous alveoli (6) Vestibular fold (7) Respiratory epithelium (look above) (8) Special epithelium of vocal fold (look above) (9) Ventricle of larynx
23
Histology 2nd Semester D.A.T.W
Larynx 3rd picture •
• • •
Respiratory epithelium -> pseudostratified columnar kinociliated epithelium (1) kinocilia (2) basal bodies (3) reserve cell line (replace cells in the epithelium if necessary
24
Histology 2nd Semester D.A.T.W
Larynx 4th picture • • • •
(1) Hyaline Cartilage (2) Ossified Cartilage (3) White fat cells (5) Red bone marrow
25
Histology 2nd Semester D.A.T.W Part II – Theory • •
• • •
26 The larynx is the entrance of the channel system leading into the lungs -> its entrance is located beneath the epiglottis at the root of the tongue It consists of the following parts o Epiglottis -> made up of elastic cartilage -> forms a lid which closes during swallowing in order to prevent food from entering the pharynx o Basic skeleton formed by thryroid and cricoids cartilages (both made up of hyaline cartilage) o Vestibule -> empty room beneath the epiglottis -> formed by quadrangular membrane and thyroid cartilage (hyaline cartilage) Quadrangular membrane • o Vocal folds False Vocal Fold • is made up superior invagination of the inner lining of the larynx (produced by the vestibular ligament on the inside) Inbetween -> laryngeal ventricle (rima glottidis) -> the ventricular fold and the ventricle are important for resonance in sound formation True Vocal Fold -> made up by thyroarytenoid muscle (containing vocalis muscle on outer border) and vocal ligament • Inside the TRUE vocal fold no glands can be found in underlying C.T. • Is easily to identify because it’s the fold which contains skeletal muscle in cross section -> the “corner” right beneath the epithelium which does not contain muscle resembles the vocal ligament • The surface epithelium of the vocal fold is NOT the usual one for respiratory organs BUT stratified-squamous-nonkeratinizing epithelium -> necessary due to the high amount of mechanical stress the vocal fold is exposed to Other muscles can be found in the larynx slide but besides the thyroarytenoid muscle you don’t have to identify any (following my seminar teacher) In older people the hyaline cartilage of the larynx (thyroid and cricoid cartilage) tend to ossify (enchondral ossification) -> visible on slide (sometimes even bone marrow can be seen) The C.T. of larynx contains mixed mucous glands -> can be seen on special PAS slides with high intensity
Histology 2nd Semester D.A.T.W
27
Histology 2nd Semester D.A.T.W
Question 7 – Trachea HE Part I – Histological appearance Magnification not high enough to mark everything • (1) Innermost layer -> respiratory epithelium • 2nd layer -> lamina propria o Lymphocytes o Fibroblasts • 3rd layer -> submucosa o Blood vessels • ( 4) 4th layer -> hyaline cartilage • (5) membranous part • 5th layer perichondrium -> loose C.T. • Smooth muscle
28
Histology 2nd Semester D.A.T.W
29
Trachea 2nd picture • • • • • • • • •
(1) pseudostratified columnar epithelium with kinocilia (2) basement membrane (3) mucosa (4) elastic membrane (5) submucosa (6) goblet cell -> not stained but visible (7) Muocous alveoli (8) Serous alveoli (9) Indention of the surface epithelium
Histology 2nd Semester D.A.T.W
30
Trachea 3rd picture • • • • • • • • •
Membranous part of trachea (1) epithelium (2) basement membrane (3) mucosa (4) submucosa (5) smooth muscle (trachealis muscle) (6) hyaline cartilage (7) mucous alveoli (8) serous alveoli (9) loose C.T.
Histology 2nd Semester D.A.T.W Part II – Theory • • • •
31 The Trachea is the continuation of the larynx -> it is a 10-12cm long tube which ends up in the branching off into the two principal bronchi It consists of hyaline cartilage segments which are hold together posteriorly by a connective tissue membrane in which smooth muscle is embedded (trachealis muscle) The layers of the trachea are made up following the general layers of respiratory organs (look at general theory 2nd part) The lamina propria contains MALT which protects the respiratory airway
Histology 2nd Semester D.A.T.W
Question 8 - Lung Part I – Histological appearance • • • • • • • •
(1) Terminal Bronchus (hyaline cartilage (5) is a sign (2) bronchioli (3) terminal bronchioli (4) alveolar duct (8) respiratory bronchioli (5) hyaline cartilage (6) (7) blood vessels (branches of pulmonary veins) + alveoli
32
Histology 2nd Semester D.A.T.W Lung 2nd picture • • •
(1) respiratory bronchioli -> smooth muscle contracted -> star shaped lumen (2) alveoli (3) vein -> branch of pulmonary veins
33
Histology 2nd Semester D.A.T.W Lung 4th slide (DEMONSTRATION ONLY) Vessels were perfused with ink Branch of pulmonary veins Alveolar capillaries
34
Histology 2nd Semester D.A.T.W
35
Lung 5th slide (ORCEIN) Staining of elastic fibers • On the left -> bronchiole • On the right -> branch of pulmonary artery
Histology 2nd Semester D.A.T.W
36
Lung 6th slide (ORCEIN) •
Bronchiolus with strong elastic membrane (1)
Histology 2nd Semester D.A.T.W Lung 6st slide (ORCEIN)
37 •
•
Elastic fibers form basket like meshwork in the wall of the alveoli -> during passive expiration they aid by retaining their original shape -> elastic fibers pull back together
Histology 2nd Semester D.A.T.W Part II – Theory • •
•
•
The lung is the location of O2 – Co2 exchange in the blood and a vital organ for human life Bronchi o Trachea -> divides by dichotonic divisions and from there the bronchus tree is formed o 1st division -> primary bronchi Left primary bronchus (oblique and longer than right because it has to wrap round heart) Right primary bronchus (short and straight -> all inhaled particles usually enter straight into the right PB and enter the right lung) nd o 2 division -> Secondary OR Lobar bronchi -> after entering the lung the primary bronchi divide into lobar bronchi (corresponding to the number of lobes Left: 2 lobes Right: 3 lobes rd o 3 division -> Tertiary or Segmental bronchi -> each lobe consists of several bronchopulmonary segments Andrea said in the practice the basic rule is: 10 left, 10 right -> 10-10 The book says: left lung 8 segments, right lung 10 segments (I think the number is not really important) Bronchopulmonary segments are important o Each one is a functional unit of gas exchange o Consisting of a segmental bronchus + lung parenchyma + own blood supply o The segments are separated by connective tissue septa -> infections can hardly spread across segments -> if one segment is doomed it can be removed surgically Bronchioles o Bronchopulmonary segments are further subdivided into segments -> pulmonary lobules o -> each one is supplied by a bronchiole which is a subdivision of a segmental bronchus o Bronchioles are air conducting ducts with 1mm or less in diameter o The bigger ones are divisions of the segmental bronchus o -> the last but one branching results in the terminal bronchiole -> after it branches into the respiratory bronchiole (1st area of gas exchange) o
38
Histology 2nd Semester D.A.T.W •
•
Alveoli o As mentioned above, respiratory bronchioles are the first ones which provide surface for gas exchange o -> the biggest surface however is provided by “alveoli” which sit at the end of respiratory bronchioles in the form of alveolar sacs o Alveoli are terminal air spaces -> actual location of gas exchange in lungs o Each one is surrounded by a network of capillaries o Their combined surface area is 75m2 (tennis court) per lung (150 altogether) Changes in histological structure o Bronchi After entering the hilus of the lung, the tracheal cartilages rings disappear and instead plate like cartilage forms the cartilage layer of the bronchi -> with each division and the deeper in the lung they go -> the cartilage becomes less and instead more smooth muscle is found in the walls o Bronchioles -> once the diameter of the bronchiole reaches 1mm the cartilage disappear (transition between terminal bronchiole and respiratory bronchiole) Bronchioles do not contain the typical epithelium for respiratory tissues anymore (look above) -> bigger bronchioles have simple columnar ciliated epithelium -> small bronchioles have simple cuboidal epithelium o Clara cells With the beginning of terminal bronchioli clara cells appear Their number increases from there on the deeper you go -> ciliated cells decrease in number They secrete a surface-active agent (lipoprotein) which prevents luminal adhesion of the airway -> so it doesn’t stick together once it collapses -> which happens e.g. during expiration Clara cells produce CC16 which is a protein special for the secretion fluid of airways -> its secretion decreases during lung injury -> can be measured for diagnostic purpose
39
o
•
Histology 2nd Semester D.A.T.W Alveoli Alveolar epithelium is permanently exposed to inhaled particles, pathogens, toxins etc. Its epithelium therefore contains specialized defense cells 40 Type I alveolar cells (OR Type I Pneumocytes) • Extremely thin squamous cells that line 95% of the alveolar surface (well visible on slides) • Joined by occluding junctions -> form effective barrier between air space and components of septa • These cells are not able to divide Type II alveolar cells (OR Type II Pneumocytes) • Cover 5% of alveolar surface • Cytoplasm is filled with granules -> secrete surfactant • Surfactant is extremely important for the stability of alveoli -> it reduces surface tension and prevents collapses (children with respiratory distress syndrome do not produce sufficient amounts) • Also are precursor cells of Type I pneumocytes -> after lung injury they proliferate and restore the missing type I cells Brush cells are also present in the alveoli and monitor the air quality by receptors In the alveolar connective tissue septa special macrophages are located which phagocytose RBCs which pass through the pulmonary vessels in case of heart problems that result in higher pressure of the arteries -> !! in thise case the sputum of the patient contains brown-reddish cells which are the macrophages containing the red Hemoglobin!!
Blood Supply o The lung has two types of circulation -> pulmonary circulation for gas exchange and a bronchial circulation supplying the lung tissue itself o Pulmonary circulation Deoxygenated blood leaves the heart with the pulmonary artery and is carried towards the lung (enters at the hilus) Branches of the pulmonary artery travel together with the bonchi and bronchioli to the alveolar sacs -> capillaries which surround the alveoli -> oxygenated blood is collected by venules which then travel back and form the four pulmonary veins -> the venous part of the pulmonary circulation is always located in the periphery of each bronchopulmonary segment -> distant from the respiratory passages o Bronchial circulation Bronchial arteries branch from the aorta Supplies all lung tissues besides the alveoli and their septa Bronchial and pulmonary circulations anastomose at the junction between terminal and respiratory broncholi (junction between conducting and respiratory passages)
Histology 2nd Semester D.A.T.W •
Air – Blood Barrier o Is formed by the alveolar septum o The layers at the thinnest region are (from air filled space -> blood vessel lumen) Surfactant Type I alveolar cells Basal lamina Basal lamina Capillaray endothelium -> often the two basal laminae are fused
41
4th week: Salivary glands,tongue •
• •
•
•
•
•
Histology 2nd Semester D.A.T.W
The salivary glands are the following paired 42 o Parotid glands o Submandibular glands o Sublingual glands All of them are surrounded by a dense connective tissue capsule from which septa extend inside and divide the secretory portions into lobes and lobules -> the septa contain the excretory ducts and blood vessesl supplying the gland All salivary glands contain basic secretory units (salivons) consisting of o Acinus o Intercalated duct o Excretory duct (or interlobular or secretory duct) Acinus o Term refers to berry or grape o Contains either serous or mucous cells or sometimes both (in detail below) o The major salivary glands can be distinguished based on the proportion of serous to mucous glands contained Serous glands o Protein secreting cells (mainly amylase -> digestive enzyme) o -> therefore they contain RER and stain basophilic with HE staining o Have a narrow lumen o Cells have pyramidal shape with wide base towards the basal lamina o Central, roundish nuclei o In comparison to mucous glands they have a very narrow lumen Mucous glands o Secrete mucin -> viscous, glycoprotein reach fluid o Stored in mucinogen granules which are located in the apical part of the cells -> lost during fixation method o Stain pale with HE -> mainly contain golgi (and the granules are lost during the staining method) o Nucleus is flat and located at basal membrane o Wider lumen Myoepithelial cells o Contractile cells which lie between cell membrane and basal lamina of the mucous/serous glands o Their contraction moves secretory products towards the excretory ducts o Difficult to see in HE staining but they are there
•
•
Ducts Histology 2nd Semester D.A.T.W o Intracalated or intralobular duct Within the lobule Leading from the acinus 43 Simple cuboidal epithelium Possess carbonic anhydrase activity • Secrete bicarbonate ions into the acinar products • Absorb chlorine ions from the acinar products o Striated duct Towards the end of the lobule (see below in pictures) the duct becomes bigger and its epithelium changes from cuboidal to columnar gradually This part of the duct system is called striated because its basal membrane shows infoldings which contain a lot of mitochondria -> these are necessary for all the transport processes -> absorption of Na+ and secretion of K+ and HCO3o Excretory (secretory) ducts Big duct inbetween the lobules in which the striated ducts empty out Connects to oral cavity Epithelial variances (depending on width of lumen) • In small parts -> simple cuboidal epithelium • In medium parts -> pseudostratified columnar epithelium • In large parts -> stratified columnar epithelium • -> in close vincinity to the opening into the oral cavity -> stratified non-k squamous epithelium can be seen Saliva o Performs protective and digestive functions Moistening of oral mucosa Moistening of dry foods -> aid in swallowing Medium for suspended food materials to chemically stimulate taste buds Providing a buffer inside the oral cavity (high concentration of bicarbonate ions) Digests carbohydrates by the help of amylase (breaks up glycosidic bonds) Fights bacteria by the help of lysozyme
Histology 2nd Semester D.A.T.W
Question 10 – Parotid Gland Part I – Histological appearance • • • •
(1) C.T. septa (2) serous alveoli (3) fat cells (4) intercalated ducts
44
Part II – Theory • • • • • • •
Largest of the major salivary glands Located in front of of ear -> parotid duct is even macroanatomical structure -> enters the oral cavity opposite to the 2nd upper molar tooth Only serous glands can be found Relatively large amounts of adipose cells Facial nerve crosses and can appear as tangential or cross sections in slide Mumps is a viral infection of the parotid gland which can damage the facial nerve
Histology 2nd Semester D.A.T.W
45
Histology 2nd Semester D.A.T.W
Question 11 – Sublingual Gland HE Part I – Histological appearance • • • •
(1) C.T. septum (2) mucous alveoli (3) Interlobular duct (4) fat cells
46
Histology 2nd Semester D.A.T.W
Sublingual gland 2nd picture (MUCICARMINE) DEMONSTRATION ONLY • (1) C.T. Septum • (2) Mucous alveoli • (3) Serous alveoli • (4) fat cells This slide has been stained with a specific staining (mucicarmine) which stains mucinogen granules found in high amounts in the mucous alveoli
47
Part II – Theory • • • • •
Smallest of major salivary glands Located in floor of oral cavity (anteriorly and superiorly to submandibular glands) Their ducts empty into the ducts of the submandibular glands as well as directly into the oral cavity Mainly mucous glands are seen Gianuzzi Half Moons
Histology 2nd Semester D.A.T.W
48
Histology 2nd Semester D.A.T.W
Question 13 – Sublingual Gland PAS - HE
49
Part I – Histological appearance • • • •
(1) Interlobular duct (2) mucous alveoli (3) serous alveoli (4) myoepithelial ring surrounding the alveoli PAS stains the glycoproteins in the mucous granules as well as the myoepithelial contractile ring surrounding the alveoli of the glands
Histology 2nd Semester D.A.T.W
Sublingual gland 2nd picture (PAS-H) • • •
(1) Mucous alveoli (2) Serous alveoli (3) Myoepithelial ring
50
Part II – Theory • • •
Histology 2nd Semester D.A.T.W
In this special staining the Periodic-Acid-Schiff staining is specific for the glycoproteins in the mucus -> mucinogen granules are stained !! Remember that during the fixation a certain amount of mucinogen granules is lost -> this is why in the slide not all the glands or even only a partial gland 51 appear to be stained by PAS !! The basal lamina is also stained by pas due to high glycoprotein content
Histology 2nd Semester D.A.T.W
Question 12 – Submandibular Gland HE Part I – Histological appearance • • •
(1) Serous alveoli (2) Mucous alveoli (3) Intercalated duct (longitudinal section)
52
Histology 2nd Semester D.A.T.W Submandibular gland 2nd picture • • •
(1) Serous alveoli (2) Mucous alveoli (3) Intercalated ducts
53
Part II – Theory • • • •
Histology 2nd Semester D.A.T.W
Located close to the mandible underneath the floor of the oral cavity Distinct duct from each one running anteriorly and opening into the cavity just lateral of the inferior frenulum of the lip (look anatomy atlas) Contains mostly serous and some mucous glands Gianuzzi Half Moons
54
Tongue • • • •
Histology 2nd Semester D.A.T.W
The tongue is the strongest muscle in the body (following Marius Opsahl MD PhD) 55 It contains intrinsic skeletal muscle in all three dimensions (although no specific slides exist about it you can see them in the papillae slides) The dorsal surface of the tongue if divided into an anterior 2/3 and a posterior 1/3 -> the borderline is formed by the sulcus terminalis Lingual papillae o Found anteriorly to the terminal sulcus o Together with their taste buds they constitute the specialized mucosa of the oral cavity o Four types are known Filiform papillae • Are the smallest and most numerous (in humans) • Responsible for the whitish colour of the tongue • Covered with highly keratinized stratified squamous epithelium • Do NOT contain taste buds • Have mechanical role Fungiform papillae • Mushroom shaped • Scattered inbetween the filiform papillae -> stick out between them (visible with naked eye) • Higher amount towards apex of tongue • Contain taste buds (caliculi gustatory) in their stratified squamous non keratinized epithelium Circumvallate papillae • Largest papillae • Dome shaped • Located anteriorly to terminal sulcus (8-12 only) • Stratified squamous non keratinized epithelium with taste buds • Surrounded by invaginations underneath which Ebner`s glands are located -> their ducts empty out into the base of the invagination > flushes out the chemical taste carriers -> so the next taste sensation can be detected in rapid turnover rate Foliate papillae • Located on lateral sides of tongue • Visible by naked eye as parallel low ridges separated by deep mucosal clefts -> aligned in a right angle to axis of tongue (look ross book p. 479, figure 16.3) • Contain taste buds • In the course these are only shown on the rabbit slide
Histology 2nd Semester D.A.T.W
Question 14 – Filiform/Fungiform papillae HE Part I – Histological appearance
56
Histology 2nd Semester D.A.T.W
57
Histology 2nd Semester D.A.T.W
58
Histology 2nd Semester D.A.T.W
59
Histology 2nd Semester D.A.T.W
Question 15 – Papillae Vallate HE Part I - Histological appearance • • • • •
(1) stratified squamous non keratinized epithelium (2) taste buds (caliculi gustatory) (3) excretory duct of Ebner´s gland (4) Ebner´s mixed salivary gland (5) skeletal muscle of tongue
60
Histology 2nd Semester D.A.T.W
Papilla vallata 2nd picture • • • • •
(1) epithelium (look above) (2) taste buds (3) excretory duct of Ebner´s gland (4) Ebner´s serous salivary gland (5) C.T. papillae
61
Histology 2nd Semester D.A.T.W
Rabbit Foliate Papillae (demonstration only!) Part I - Histological appearance
62
Histology 2nd Semester D.A.T.W
Question 16 – Lingual Tonsil HE Part I - Histological appearance • • • •
(1) stratified squamous non-keratinizing epithelium (2) germinal centers (3) mucous alveoli (4) skeletal muscle of tongue
63
Histology 2nd Semester D.A.T.W
Lingual Tonsil 2nd picture • • • • •
(1) germinal center (2) corona radiata (3) mucous alveoli (4) skeletal muscle (5) detritus -> death desquamated epithelial cells which are „trapped“
64
5th week: Lip, tooth, development of teeth 1)
Histology 2nd Semester D.A.T.W
Tooth • The mature tooth consists of the following parts 65 o Enamel layer which ends shortly beneath the beginning of the gingiva with the cementoenamel junction -> it forms the crown of the tooth -> it is the hardest substance in the body o Dentin Layer which starts beneath the enamel of the crown and continues downward until the apical foramen of the root -> it is the thickest of the three layers o Cementum Layer which replaces the enamel as the outer layer covering the dentin after the cementoenamel junction -> it is the thinnest of the three layers The cementum has two parts • Non-cellular cementum -> forms the upper part of it • Cellular cementum -> forms lower part until it ends with the root o Central Pulp cavity -> contains dental pulp -> loose C.T. which is highly vascularized and supplied by nerves (tooth drilling hurts!) -> those neurovascular structures enter the cavity through the apical foramen in the root • Enamel o Acellular mineralized tissue (96-98% calcium hydroxyapatite) o Derived from epithelium (look development of tooth below) -> STAINS RED WITH AZAN o Covers the crown of the tooth (clinical crown goes until beginning of gingival, anatomical crown until cementoenamel junction) o Enamel cannot be replaced once its created o Its composed of “enamel rods” which are 4µm wide, 8µm high and 2000µm long o Striations within the enamel system Oblique or horizontal thick lines show the rhythmic growth of the enamel in the developing tooth (like age lines of a tree in cross section) -> they are called “retzius lines” Vertical lines are the spaces inbetween the enamel rods and are called “hunter-schreger lines” they mark the way which the enamel synthesizing cells (adamantoblasts or ameloblasts) took during the secretion of the enamel matrix (look below for details) o Although consisting only of small organic parts the enamel can be decalcified by acid producing bacteria which act on food products that have not been brushed of the enamel surface (look at canines of Marius Opsahl MD PhD) -> this is the base for dental caries formation • Dentin o Dentin lies beneath the enamel or cementum respectively o It forms most of the tooth substance o Contains less inorganic material (70% hydroxyapatite) o Derived from mesenchyme -> STAINS BLUE WITH AZAN o Dentin is secreted by odontoblasts (look below) which form an epithelial layer on the inner surface of it -> facing the pulp cavity
•
Cementum Histology 2nd Semester D.A.T.W o Thinnest layer of tooth o Composition is similar to that of bone -> 65% anorganic substances, contains lacunae and canaliculi o In opposition to bone it is NOT vascularized 66 o On the outer surface facing the gingival or bony surface, cementoblasts can be seen o Has non - cellular part (where it is covered by gingiva outside) and a cellular part (where it is covered by bone from the alveolus of mandible or maxilla) o -> from the cellular part collagenous and elastic fibers extend into the bone to fix the tooth
•
Development of Tooth o During embryonic life the teeth start to develop (period) o The first sign is the appearance of the dental lamina from which the enamel organ grows into the underlying mesenchyme o From there three stages can be observed 1) Bud stage: from the dental lamina the bud stage develops -> a roundish structure extends in the mesenchyme beneath -> structure is covered by outer enamel cells and contains stellate reticulum (this is a meshwork of epithelioreticulocytes [look at thymus for description] which only appears in the thymus besides this location) 2) Cap stage: on the side opposite to the dental lamina a concave infolding appears 3) Bell stage: further growth of the enamel organ results in the bell stage -> now the five important layers of the developing tooth can be distinguished • Outer enamel epithelium • Stellate reticulum • Stratum intermedium • Inner enamel epithelium (adamantoblasts) • Dental papilla -> Now on the inner side of the adamantoblasts another cell layer appears and develops into distinct columnar cells -> preodontoblasts -> later odontoblasts (see below) -> from this stage the enamel and dentin layers of the tooth develop o Enamel Synthesized by “adamanto- or ameloblasts” Shortly before the production of enamel starts two things happen • The dental lamina starts to degenerate • The odontoblasts start to lay down a small layer of predentin -> on this layer the enamel is starting to be secreted Now amelogenesis (the synthesis of enamel) starts and it can be divided into 2 phases
•
•
Amelogenesis Histology 2nd Semester D.A.T.W o Phase 1 -> Secretory stage or matrix production During this stage the basic framework for the future enamel is laid down in form of an organic protein-fiber (reticular) matrix (similar to that in bone formation) Performed by “secretory stage adamantoblasts” -> these cells are polarized columnar cells -> their apical pole is facing the newly synthesized 67 fibers and facing away from the direction of movement -> the apical pole contains “tome´s process” o Phase 2 -> Maturation stage Now the preformed matrix is mineralized by • A) the removal of organic materials • B) the influx of calcium and phosphate This function is performed by maturation stage adamantoblasts which differentiate from secretory adamantoblasts -> they work mainly as transport epithelium sitting at the end of the matrix -> transport organic substances out and pump calcium in These adamantoblasts border the stratum intermedium with their basal membrane -> the cells of the stratum intermedium contain alkaline phosphatases and enhance enamel calcification Dentin o Formed by odontoblasts -> columnar cells o Initially the odontoblasts sit on the side of the adamantoblasts (or inner enamel cells) which is facing towards the dental papilla -> their apical membranes are pointing towards the adamantoblasts o Now the cells retreat inward while laying down the predentin -> they leave cellular processes which elongate while they migrate further away from their initial position -> those processes communicate which each other at their ends (this area is seen as “tome`s granulation” on the slides) and send survival signals -> odontoblasts never die but stay active -> more and more dentin is produced with higher age and the pulp cavity shrinks o -> The cellular processes are embedded into the matrix into the dental tubuli which can be seen as black lines on the slide -> tome´s fibers o Dental growth is rhythmic like that of enamel -> cross striations can be seen which mark important stages of development (e.g. neonatal line which marks birth) o Dentin secretion also has two phases but only one cell type acts Phase 1 -> secretion of predentin (can be distinguished in slide as inner, more palish layer) • The predentin contains two unique proteins o Dentin phosphoprotein -> rich in aspartic acid and other calcium binding substances -> is involved in the initiation of mineralization o Dentin sialoprotein -> contains chondroitin sulphate Phase 2 -> actual mineralization of the predentin -> happens just a certain time after the secretion of predentin due to the binding of calcium by the mentioned protein
•
Cementum
Histology 2nd Semester D.A.T.W
68 Question 17 – Lip HE Part I – Histological appearance 2) Lip
• • • • • • • • • • • • • •
(1) Cutaneous part (no glands found here!) (2) Red Part -> covered by str. Squamous keratinizing epithelium -> keratin layer is very thin (3) Mucous part -> str. Squamous non-keratinizing epithelium (4) stratified squamous keratinizing epithelium with normal layer of keratin (5) hair follicle (6) sebaceous gland (7) sweat gland (8) melanocytes at base of hair follicle (9) C.T. papillae -> vascularized -> red color of lip is because the blood is “visible” through the thin layer of keratinization (10) peripheral nerve (11) skeletal muscle (orbicularis oris) (12) artery (13) dermis (14) subcutaneous layer
Histology 2nd Semester D.A.T.W
69
Part II - Theory
Histology 2nd Semester D.A.T.W
70
Histology 2nd Semester D.A.T.W
Question 18 – Ground Tooth Fuchsin Part I – Histological appearance • • • • • • •
(1) Pulp cavity (2) Dentin (3) Enamel (4) Dental Tubuli (5) Interglobular spaces (6) Tomes granulation (7) Odontoblasts
71
Histology 2nd Semester D.A.T.W
Ground tooth 2nd picture • • • • •
(1) Dentin (2) Tomes granulation (3) A-cellular cementum (4) cellular cementum (5) lacunae of cementocytes
72
Histology 2nd Semester D.A.T.W
Ground tooth 3rd picture • • •
(1) Dentin (2) Tomes granulation (3) lacuna of cementocyte
73
Histology 2nd Semester D.A.T.W
Ground tooth 4th picture • •
(1) A-cellular cementum (2) Dentin
74
Histology 2nd Semester D.A.T.W
Ground tooth 5th picture • • •
(1) A-cellular cementum (2) Dentin (3) Tomes Granulation
75
Histology 2nd Semester D.A.T.W Ground tooth 6th picture • • •
(1) Dentin (2) A-cellular cementum (*) empty space in the middle is the pulp cavity
76
Histology 2nd Semester D.A.T.W
77 Ground tooth 7th picture • • • • • • • •
(1) Enamel (2) Hunter-Schreger lines (3) Retzius lines (4) Adamantoblasts (5) Tomes granulation (6) Dentin (7) Dental tubuli (8) Interglobular spaces
Histology 2nd Semester D.A.T.W
78 Ground tooth 8th picture • • • • •
(1) Enamel (2) Hunter-Schreger lines (3) Retzius lines (4) Dentin (5) Tomes granulation
Histology 2nd Semester D.A.T.W
79 Ground tooth 9th picture • • • • •
(1) Enamel (2) Adamantoblasts (3) Tomes granulation (4) Dentin (5) Interglobular spaces
Part II – Theory •
• •
Histology 2nd Semester D.A.T.W
Ground tooth is preparated in the same way as ground bone o Thin slices are cut with a diamond cutter o The slice is polished o The slice is soaked in fuchsin -> accumulates in spaces that were occupied by ORGANIC substances during life (e.g. tomes fibers or cells) o Fuchsin excess is polished off Spaces in which organic substances have been during life appear reddish dark -> it is important to know that these (e.g. tomes fibers) do not show the cells or organic materials but the empty spaces remaining (-> dental tubuli or canaliculi) Several different preparations where made o Cross sections at close to the root -> here you see the dentin and cementum as well as the pulp cavity which now appears as an empty space o Cross sections at the crown -> here you see the dentin and enamel as well as the dentoenamel junction o Longitudinal sections in different locations (and recorded at different magnifications)
80
Histology 2nd Semester D.A.T.W
Question 19 – Tooth Development Early HE Part I Histological Appearance • • • • • • • • • •
(1) Epithelium of oral cavity (stratified squamous non keratinizing epithelium) (2) Dental lamina (3) Outer Enamel Cells (4) Inner Enamel Cells (5) Stellate reticulum (6) Stellate papilla (7) intramembranous bone formation (8) Hertwigs root sheath (9) Dental sac (10) later odontoblasts
81
Part II - Theory
Histology 2nd Semester D.A.T.W
82
Histology 2nd Semester D.A.T.W
Question 20 – Tooth development early AZAN Part I – Histological Appearance • • • • • • • •
(1) Epithelium of oral cavity (2) Dental lamina (3) Outer enamel cells (4) Inner enamel cells (5) Stellate reticulum (6) Hertwig´s root sheath (7) Dental sac (8) later odontoblasts
83
Part II - Theory
Histology 2nd Semester D.A.T.W
84
Histology 2nd Semester D.A.T.W
Question 21 – Tooth development advanced HE Part I – Histological appearance • • • • • • • • • • • • • •
(1) Epithelium of oral cavity (2) Dental lamina (3) Outer enamel cells (4) Stellate reticulum (5) Inner enamel cells (adamantoblasts) (6) Enamel (7) Dentin (8) Predentin (9) Odontoblasts (10) dental papilla (11) Hertwig´s root sheath (12) Dental sac (13) 2nd developing tooth (14) intramembranous bone formation
85
Histology 2nd Semester D.A.T.W
86 Tooth 2nd picture • • • • • • • •
(1) Stratum intermedium (2) Inner enamel cells (adamantoblasts) (3) Enamel (4) Dentin (5) Predentin (6) Odontoblasts (7) Dental papilla (8) Stellate reticulum
Part II - Theory
Histology 2nd Semester D.A.T.W
87
Histology 2nd Semester D.A.T.W
Question 22 – Tooth development advanced AZAN Part I – Histological appearance • • • • • • • • •
(1) Surface epithelium of oral cavity (2) Outer enamel cells (3) Inner enamel cells (adamantoblasts) (4) Enamel -> stains red (5) Dentin -> stains blue (6) Stellate reticulum (7) Dental papilla (8) Hertwig´s root sheath (9) Intramembranous bone formation -> stains blue AZAN stains tissues with epithelial origin red (ENAMEL) and tissues of connective tissue origin blue (DENTIN, BONE)
88
Histology 2nd Semester D.A.T.W
89
Histology 2nd Semester D.A.T.W
90
Part II - Theory
Histology 2nd Semester D.A.T.W
91
6th week: Esophagus,stomach • • •
Histology 2nd Semester D.A.T.W
The alimentary canal which extends from the esophagus to the distal part of the anal canal is a hollow tube with varying diameter The wall of it is formed by three distinct layers which show special characteristics dependent on the part of the canal (e.g. esophagus or pylorus of stomach) Layers o Tunica Mucosa Outermost layer Epithelium differs throughout the canal dependent on function of the part • Serves as barrier which separates lumen of canal from rest of body prevents antigens from entering the body as well as physical damage (e.g. in esophagus) from hard parts in ingested food • In some parts it serves as selective barrier which is very important for the absorption of nutrients • The absorptive function of the mucosa is further enhanced by exvaginations of it (Villi not to mix up with microvilli which are also present) these villi enhance the surface area of the digestive tract and enhance absorption of nutrients Lamina propria tissue underlying the epithelium consisting of loose connective tissue • Contains mucous secreting glands (e.g. in esophagus and anal canal) • Contains capillaries (fenestrated in regions of absorption) • Contains diffuse lymphatic tissues and nodules Lamina muscularis (or muscularis mucosae) (NOT to mix up with the muscularis externa which is the 3rd main layer) • Layer of smooth muscle at bottom of mucosa forms border to submucosa • Muscle cells are arranged in inner circular and outer longitudinal layer • Contraction of this muscle produces movement of the mucosa forming ridges and valleys that facilitate absorption and secretion o Tunica Submucosa Dense irregular connective tissue Contains larger blood vessels which send branches into the mucosa Contains lymphatic tissue Contains Meißner´s Plexus submucosal nerve plexus consisting of • Sympathetic fibers only postganglionic • Parasysmpathetic fibers ganglions are found within the cells of the organ represent enteric nervous system o Preganglionic fibers o Ganglionic cells o Postganglionic fibers
92
• o
o o
o
Histology 2nd Semester D.A.T.W Tunica muscularis (or muscularis externa) Consists of two relative thick layers of smooth muscle which have different orientation Inner layer 93 • Runs circuclary oriented in the tube Outer layer runs longitudinally around the tube so if you see the cells in cross section than you have a cross section of the organ in your slide, if you see them in longitudinal section you have a longitudinal cut in your slide Inbetween the two layers you find a thin connective tissue layer which contains the myenteric plexus (or Auerbach´s plexus) which contains • Ganglion cells and postganglionic fibers of parasympathetic nervous system • Blood vessels • Lymphatic vessels The slow and rhythmic contraction of these two muscle layers under control of enteric nervous system produces peristalsis which moves the contents of the intestinal tract towards the anal canal At several points along the digestive tract these muscles form sphincters which are able to obstruct the tube I will mention them at the reference slides theory Tunica Subserosa Only present at locations of peritoneal covering (abdominal cavity) Tunica Serosa Only present at locations of peritoneal covering (abdominal cavity) Serous membrane consisting of mesothelium (look 1st semester) and small amount of connective tissue It resembles the peritoneal layer which is a macroanatomical structure found to cover the organs of the abdominal cavity Continuous with mesentery and lining of abdominal cavity Tunica Adventitia In case of no peritoneal covering Thick layer of loose connective tissue
Stomach specified theory • •
• •
•
Histology 2nd Semester D.A.T.W
Stomach is expanded part of digestive system lying beneath the diaphragm receives bolus from esophagus mixes with gastric secretions in the stomach, is partially digested and becomes chyme chyme passes into small intestine for further digestion and absorption 94 Is divided into three regions (histologically note that in macroanatomy there is a fourth region) o Cardiac region (cardia) small part at the opening of the esophagus o Fundic region (fundus or corpus ventriculi) largest part of the stomach, located between cardia and pylorus o Pyloric region (pylorus) part at the “exit” of the stomach, close to the pyloric sphincter The same structural organization as mentioned above exists in the stomach but some “special features” in the layers are present which depend on the region Gastric Mucosa o Contains longitudinal folds called “rugae” prominent in the lower narrow region and poorly developed in the upper wider region o When the stomach distends the rugae disappear they provide expansion capacity (and not increased surface area for absorption!!) o On the mucosal surface, openings can be found at higher magnification gastric pits openings gastric glands (see below) open into them o Epithelium of stomach is simple columnar it is a special secretory epithelium the cells are designated surface mucous cells which secrete mucus can be stained distinctly by PAS !!NOTE that these cells ARE NOT GOBLET CELLS (as found in small intestine e.g.) o The mucus produced coats the surface of the epithelium and has two main functions Protection from abrasion due rougher components of the chime Protection from the low pH level in the gastric environment (see below) by a high bicarbonate concentration in the mucus (!! In order not to neutralize the whole lumen of the stomach the bicarbonate content is contained in the viscous mucous coat next to the epithelium and does not mix with the fluids within the stomach lumen!!) still alcohol and certain drugs can damage the surface epithelium and enter the lamina propria of the stomach Gastric Glands (OR Fundic Glands) o Are present throughout the whole fundus o Simple, branched, tubular glands (well visible on sections) extend from bottom of gastric pits to the muscularis mucosae ( to the border of mucosa and submucosa) o Segments Neck segment long and narrow (well visible) • Contains a region called “isthmus” site of cell replication mucous secreting SURFACE cells replicate here and migrate upwards towards the epithelium; other cells migrate downward and maintain the epithelium of the fundic gland Base short and wide (can be divided into two or three segments) o Secretion Cells of gastric glands secrete 2L of gastric juice per day Components of gastric juice • Water and electrolytes •
• •
o
Histology 2nd Semester D.A.T.W
HCL produces pH of 1-2 in gastric juice o Secreted by parietal cells (see below) o Digests dietary protein 95 o Cleaves pepsinogen to pepsin o Destroys bacteria (bacteriostatic function) besides heliobacter pylori which coats itself with an alkaline coat to survive • Pepsin o Secreted as inactive precursor pepsinogen by chief cells o Hydrolizes proteins into small peptides • Mucus o Forms physiologic gastric mucosa barrier by containment of bicarbonates neutralize low pH level of gastric juice • Intrinsic factor (also well known from physiology) o Glycoprotein which binds vitamin B12 necessary for its absorption in the ileum o If absent PERNICIOUS ANEMIA due to lack of vitamin B12 Cells of the gastric glands Mucous neck cells • Found in neck ☺ • Shorter than the surface mucous secreting cells and exhibit less prominent mucous characteristics • Mucus secreted by it is more soluble than surface mucus • Their secretory activity is stimulated by the vagus nerve only during stomach activity Chief cells • Found in base of gland • Protein secreting cells with abundant rER stain basophilic (easy to identify with HE) • Secrete pepsinogen turns to pepsin upon contact with gastric juice Parietal cells • Found throughout the gland (also in the neck) as single cells interspersed with the others • Large, sometimes binucleated cells, triangular in sections • Stain eosinophilic (reddish) due to high amount of mitochondria needed for transport processes • Contain an intracellular canaliculi system (seen under TEM) which communicates with the lumen of the gland these canaliculi contain special transporters which are necessary for the secretion of HCL HCL must not be formed within the cell because it would destroy it immediately • Secretion mechanism of HCL o H+ are produced in the cytoplasm by carbonic anhydrase (hydrolyzes H2CO3 into HCO3- and H+ look red blood cells) o Co2 necessary for this diffuses from the capillaries through the basal membrane into the cell cytoplasm
•
Histology 2nd Semester D.A.T.W Transport of H+ across the membrane into the lumen of the canaliculi is facilitated by an K+/H+ ATPase pumps H+ out and K+ in o Transport of Cl- across the membrane into the caniliculi is facilitated by K+/Cl- uniporters 96 o NOW HCL forms from the secreted H+ and Cl- ions o HCL secretion is stimulated by the hormone gastrin as well as histamine and acetylcholine • Parietal cells also secrete the intrinsic factor Enteroendocrine cells • Found in base of gland (book says they are found everywhere with prevalence in the base, Andrea says base) • Small cells sitting on the basal lamina • Stain basophilic (as well as chief cells) • Contain VIP (Vasointestinal active peptide) • Secrete HORMONES (e.g. GASTRIN) into the blood stream via the capillaries located beneath them • Can be differentiated from chief cells by the following characteristics o Chief cells have their nuclei close to the basal part of membrane since they secrete their products into the lumen of the gland their granules are located above the nucleus to leave the cell at the apical membrane o Enteroendocrine cells have their nuclei close to the apical membrane since they secrete their products into the blood stream of the underlying capillaries their secretory granules are located beneath the nucleus to leave the cells across the basement membrane For special characteristics of the three regions of the stomach look at theory beneath their pictures o
•
Histology 2nd Semester D.A.T.W
Question 23 – Esophagus HE
97
Part I – Histological appearance • • • • • • • •
(1) stratified squamous non-keratinizing epithelium (2) Lamina Propria (3) Muscularis mucosae (smooth muscle in cross section) (4) submucosa (5) inner layer of tunica muscularis (smooth muscle) (6) Outer layer of tunica muscularis (7) Mucous glands (8) Tunica adventitia ( since esophagus is not part of abdominal cavity, no peritoneal lining is found and therefore no serosa)
Histology 2nd Semester D.A.T.W
Esophagus 2nd picture • • • • • •
(1) Surface epithelium (2) Connective Tissue Papilla (3) Muscularis mucosae (4) Tunica muscularis inner circular layer (5) Mucous glands (6) Tunica muscularis outer longitudinal layer
98
Histology 2nd Semester D.A.T.W Esophagus 3rd picture • • • • •
99
(1) Stratum planocellulare (2) Stratum polygonale (3) Stratum basale (4) Connective Tissue papillae (5) Loose connective tissue of lamina propria
Histology 2nd Semester D.A.T.W Esophagus 4th picture •
• •
100
(1) Myenteric plexus of muscular layer basophilic nerve surrounded by satellite cells (2) smooth muscle in longitudinal section (3) smooth muscle in cross section
