Type of tissue: A longitudinal section of the larynx. Staining method: Hematoxylin and Eosin. Special features: 1. Anatomical features of the larynx:

Vestibule. Vestibular fold. Ventricle. Sub-glottis. Glottis. Conus elasticus. Vocal ligament. Vocalis. Thyroid cartilage. Cricoid cartilage.

2. In this slide, the main focus is on the vocal fold and on the vestibular fold.

3. Orientation: In the lowest magnification, The vestibular fold has glands in the submucousa. In the lowest magnification the vocal fold does not have glands in the submucousa.

4. The vestibule and vestibular fold are divided into five layers: Epithelium pseudo stratified columnar ciliated epithel with goblet cells: (cilia, basal bodies, basement membrane). Lamina propria A C.T layer that contains some lymphocytes. Submucousa A loose C.T layer that has mixed salivary glands. The serous acini are dark and the mucous acini are clear. Dense C.T layer the quadrangular membrane. Perichondrium and hyaline cartilage (the thyroid cartilage).

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5. The vocal fold is divided into four layers: Epithelium stratified squamous non keratinized epithel. Lamina propria appears as white spaces. This lamina propria is composed of loose C.T that contains a lot of H2O and it can accumulate more H2O and grow. (in case of an anaphylactic shock the accumulation of H2O will cause an obstruction of the air ways). Dense C.T layer the upper edge of the conus elasticus and the vocal ligament. Striated muscle (vocalis muscle). Perichondrium and hyaline cartilage (the thyroid cartilage).

There is no submucousa!

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6. The sub glottis is divided into five layers: Epithelium pseudo stratified columnar ciliated epithel with goblet cells: (cilia, basal bodies, basement membrane). Lamina propria becomes completely loose C.T Submucousa A loose C.T layer that has mixed salivary glands. The serous acini are dark and the mucous acini are clear. Muscular layer vocalis and part of the thyroepiglotic muscle. Perichondrium and the hyaline cartilage (the thyroid cartilage).

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Type of tissue: A cross section of the trachea. Staining method: Hematoxylin and Eosin. Special features: 1. The trachea is composed of two parts:

Cartilaginous part interconnected by C.T. Membranous part a smooth muscle which connects the two open ends of each cartilage ring.

2. When we look at the specimen in the lowest magnification we can identify in the postero-lateral part a piece of the trachea that shows both parts.

3. Surrounding the trachea are blood vessels, nerves and adipocytes that accompany the tissue.

4. Classification of the cartilaginous part: (from the lumen) Epithel: pseudo stratified columnar ciliated epithel with goblet cells. (the basement membrane is very thick). Lamina propria loose C.T with a high amount of lymphocytes. This lymphatic tissue is part of BALT (bronchus associated lymphoid tissue). Sub-mucousa loose C.T with mixed salivary glands. (serous are dark and mucous are clear). Hyaline cartilage. Adventitia loose C.T. (because the organ is located in the mediastinum). Adventitia is the outermost connective tissue covering of any organ, vessel, or other structures.( In contrast to serousal surfaces which cover peritoneal, pericardial and pleural surfaces). Between the mucousa and submucousa is an elastic membrane barrier but it is not stained in H&E.

5. Classification of the membranous part: (from the lumen) Epithel: pseudo stratified columnar ciliated epithel with goblet cells. (the basement membrane is very thick). Lamina propria loose C.T with a high amount of lymphocytes. This lymphatic tissue is part of BALT (bronchus associated lymphatic tissue). Sub-mucousa loose C.T with mixed salivary glands. (serous are dark and mucous are clear). Smooth muscle layer regulates the diameter of the bronchial lumen. Adventitia loose C.T. (because the organ is located in the mediastinum). Adventitia is the outermost connective tissue covering of any organ, vessel, or other structure There is no cartilage!

trachea

esophagus

Cartilaginous part

Membranous part

Epithel Lamina propria submucousa cartilage

Epithel Lamina propria submucousa

cartilage

adventitia

Pseudo stratified columnar ciliated epithel with goblet cells

Basal bodiesciliae

BM

Basal bodies

ciliae

Pseudo stratified columnar ciliated epithel with goblet cells

Cartilaginous part

Membranous part

Epithel

Lamina propria

submucousa

Smooth muscle

Type of tissue: A longitudinal section of the lung. Staining method: Hematoxylin and Eosin. Special features: 1. The lungs begin at the bifurcation of the trachea which creates the

bronchial tree. 2. The bronchial tree is composed of:

bronchus. Bronchioles. Terminal bronchiole. Respiratory bronchiole. Alveoli.

3. bronchus: (composition) Epithel pseudo stratified columnar ciliated epithel with goblet cells. Lamina propria loose C.T tissue with lymphocytes. Part of BALT. Smooth muscle muscularis mucousa. Submucousa. Hyaline cartilage. Adventitia.

The deeper we go inside the bronchial tree, The hyaline cartilage becomes less complete and starts to form a disc-like formation. On the other hand the smooth muscle will become more promininant and circular.

Three things change from different segments of the bronchial tree: Epithelium size changes. The cartilage disappears. The smooth muscle content increases.

4. bronchiole: (composition) Epithel pseudo stratified columnar ciliated epithel with goblet cells. Lamina propria loose C.T tissue with lymphocytes. Part of BALT. Smooth muscle muscularis mucousa.

when the cartilage disappears it is the spot where the bronchus

becomes a bronchiolus. In this segment there is no submucousa.

5. Terminal bronchiole: (composition): Epithel simple columnar epithel. Lamina propria loose C.T tissue with lymphocytes. Part of BALT. Smooth muscle muscularis mucousa.

The change between the bronchiolus and the terminal bronchiole is seen at the level of the epithelium. The epithelium becomes columnar ( a thinner layer of cells aids respiration).

6. Respiratory bronchiole: (composition): Epithel simple cuboidal epithel. Lamina propria loose C.T tissue with lymphocytes. Part of BALT. Smooth muscle muscularis mucousa.

The epithelium of the respiratory bronchioles becomes cuboidal.

This is actually the first part of the active respiratory system. The respiratory bronchioles divide into alveolar ducts that have no walls. The alveolar ducts are simply openings in the alveoli where respiration occurs.

7. alveoli: The alveoli are hollow spaces that are enclosed by a wall. The wall of

the alveoli is composed of two cell types: Pneumocyte type 1 very narrow cells that participate in gas exchange. their cytoplasm is barely seen and the nuclei are narrow.

Pneumocyte type 2 these cells have a round and large nucleus. These cells do not take part in gas exchange(directly), they secrete a lipoprotein which is a main component of surfactant. The surfactant reduces the alveolar surface tension and keeps the alveoli from adhering to each other and collapsing.

8. intra-alveolar C.T: This connective tissue is composed of high amounts of elastic fibers

that provide the elastic characteristics of the lungs. This C.T is highly vasculated.

There are two types of circulation in the lungs: Pulmonary circulation. Systemic circulation.

How to identify the different blood vessels?

Pulmonary artery accompanies the bronchi. Pulmonary vein isolated. Bronchial artery accompanies the bronchi. Bronchial vein accompanies the bronchi.

In the connective tissue layer, besides resident cells that can normally be

found, there is also a special type of macrophage that can even enter the wall of the alveoli. These are large eosinophilic cells called dust cells or alveolar macrophage. They phagocyte dust and exit the lungs via lymph nodes.

9. other: Visceral pleura a layer of simple squamous mesothelium the surrounds the lung. Clara cells these are non ciliated dome-shaped cells located between the cuboidal cells of the respiratory bronchiole. They secrete a protein called CC16 (Clara cell secretory protein 16), and a surface active agent that prevents luminal adhesion especially during expiration. Decrease in CC16 levels is a major cause of Asthma and COPD. Alveoli are lined with pneumocytes type 1 and type 2 on the alveolar wall. The gas exchange occurs in capillaries adjacent to the alveoli where a blood air barrier is formed.

The blood air barrier composed of four layer: Pneumocytes type1. Basement membrane of pneumocytes type1. Endothelium. Basement membrane of endothelium.

The whole bronchial tree is part of BALT: the bronchus associated lymphatic tissue. In the C.T there are lymphocytes and lymphatic follicles.

bronchus

bronchus

bronchiole

Pseudo stratified columnar ciliated epithel with goblet cells

Respiratory bronchiole

alveolus

Pneumocyte type2 Pneumocyte type1

capillary

Type of tissue: A cross section of the lung. Staining method:

Hematoxylin and Eosin. Indian ink this ink is injected IV and eventually reaches the blood vessels of the lungs. The ink will provide a characteristic black color.

Special features: 1. This slide shows the same structures as the lung in H&E. 2. The only focus in this slide is on the blood vessels.

Blood vessels

Respiratory bronchiole

Terminal bronchiole

bronchiolus bronchus

Simple cuboidal epithel

+ Clara cells

Simple columnar epithel

Pseudo stratified columnar ciliated

epithel with goblet cells

Pseudo stratified columnar ciliated

epithel with goblet cells

epithel

+ BALT

+ BALT

+ BALT

+ BALT

Lamina propria

+ + + + Smooth muscle

- - - + submucousa

- - - Hyaline cartilage that degenerates

into cartilage islands

cartilage

- - - + adventitia

summary

Type of tissue: A cross section of the esophagus. Staining method: Hematoxylin and Eosin. Special features: 1. The esophagus and the entire GI tract are composed of the following

layers: Epithel. Lamina propria. Muscularis mucousa. Submucousa. Muscularis externa a smooth muscle layer. Adventitia.

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2. Each layer more into details: Epithel stratified squamous non keratinized epithel. Has three layers: stratum basale, stratum spinosum, stratum plancellulare. The epithelial layer provides a mechanical protection against food irritation. Lamina propria loose C.T. this is the only part of the GI tract that is not part of MALT. Muscularis mucousa a circular smooth muscle layer. Submucousa a loose C.T layer that contains esophageal glands. These glands are composed of mucous secreting cells (lightly stained) that protect the surface of the esophagus. Muscularis externa this smooth muscle layer is sub divided into two layers:

Inner layer circular orientation. Outer layer longitudinal orientation.

The muscularis externa contains two important nervous plexi that are part of the enteric nervous system: Submucousal plexus AKA plexus. Located between the submucousa and the muscularis externa. Myenteric plexus AKA plexus. This is a thick plexus that is located between the circular and longitudinal layers of the muscularis externa.

These plexi initiate the peristaltic movement and innervate glands.

Adventitia in this case because there is no serous membrane it is an adventitia layer that is the outer most cover. It is a C.T layer that also contains nerves and blood vessels.

epithel

Lamina propria

Muscularis mucousa

submucousa

Muscularis externa

adventitia

Inner - circular Outer - longitudinal Myenteric plexus

Type of tissue: A section of the stomach. Staining method: Hematoxylin and Eosin. Special features: 1. The stomach is composed of the

following layers: Epithel. Lamina propria. Muscularis mucousa. Submucousa. Muscularis externa a smooth muscle layer. Sub serousa. serousa

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2. Each layer more into details: Epithel simple columnar mucous secreting epithel. These cells are very pail because the mucous is washed during the preparation. The mucous creates a thick layer to protect cells from the low pH of the gastric juice, and from digestive enzymes. Without it, the cells would be autolysed peptic ulcer. Lamina propria the lamina propria is a part of MALT. It is very large and very thick, and can is composed of three main parts:

Lymphoreticular C.T which is part of MALT. It provides an immunological response against foreign elements that enter the stomach. Gastric pits these are protrusions of the free surface of the stomach into the lamina propria. The gastric glands open into these pits. Gastric glands.

The cellular composition of the gastric glands includes: Mucous secreting neck cells: found in the apical part of the mucousa. From a low magnification these cells appear as white bands. The cells are round with pale cytoplasm and they secrete mucous. Parietal cells: found in the middle portion of the mucousa. These cells are large with round nuclei and an eosinophilic cytoplasm. They secrete H+ and Cl- into intracellular tubules that conduct the ions into the lumen of the stomach. The H+ provides the gastric juice its acidic pH (1-2). They also release intrinsic factor which is needed for B12 absorption. Chief cells: these cells are found in the basal part of the mucousa. They are strongly basophilic because of intensive protein production (pepsinogen), which means that there are a lot of rER in the cytoplasm. It is stored as a zymogen (pre enzyme form).

Enteroendocrine cells these cells belong to the GEP family (gastro-entero-pancreatic cells) and to the APUD family. These cells appear as dark clusters under silver impregnation. They secrete hormones into the blood or into the lamina propria that will regulate the motility and secretory activity of the GI system.

Muscularis mucousa a circular smooth muscle layer. Submucousa- loose C.T Muscularis externa a very thick muscular layer that is aimed to protect the peritoneum from the gastric content. Therefore it consist of three layers:

Inner oblique orientation. Middle circular orientation. Outer longitudinal orientation.

Sub serousa. Serousa.

epithel

Lamina propria

submucousa

Muscularis mucousa

Muscularis externa

epithel Lamina propria submucousaMuscularis mucousa

Gastric pit

Simple columnar mucous secreting epithel

Mucous secreting neck cells

Mucous secreting neck cells

Parietal cells

Chief cells

Mucous secreting neck cells

Parietal cells Chief cells

Inner oblique Middle circular Outer longitudinal

Sub serousa serousa

Type of tissue: A section of the stomach. Staining method: PAS periodic acid schiff. This is a specific staining that shows

carbohydrates in purple. In this specimen all mucous secreting cells will be stained in purple.

Special features: 1. The focus of this slide will be on the mucous secreting cells:

Surface epithelium. Mucous secreting neck cells.

Type of tissue: A section of the gastro-duodenal junction (pylorus). Staining method: Hematoxylin and Eosin. Special features: 1. In this slide the focus is on the

pylorus. The pylorus has two parts and the aim is to investigate the differences between them:

Stomach portion. Duodenal portion.

2. The stomach portion of the pylorus: (division into layers): Epithelium simple columnar epithel (mucous secreting). Lamina propria has a high amount of C.T. which is part of MALT. The lamina propria also contains glands (pyloric glands) that are composed of two cell types:

Mucous secreting cells. Enteroendocrine cells part of the APUD and GEP families They secrete hormones into the blood or into the lamina propria that will secrete peptides: VIP, Bombesin that regulate the motility and secretory activity of the GI system. No parietal and chief cells!

Muscularis mucousa a smooth muscle layer. Submucousa loose C.T

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Muscularis externa composed of three layers: Inner oblique. Middle circular. Outer longitudinal.

Sub serousa. Serousa.

3. The duodenal part of the pylorus: (division into layers): Epithelium simple columnar epithel with brush border and goblet cells. (enterocytes). Lamina propria composed of lymphoreticular C.T (MALT). It forms intestinal villi which are finger-like protrusions into the lumen of the small intestine (covered by epithelium). Within the villus are smooth muscle cells (red bands) that are detached from the muscularis mucousa. These smooth muscle bundles provide motility to the villus. Within the real/well defined lamina propria there are some structures with lumens. These are intestinal glands known as the crypts of Leiberkun.

The crypts of Leiberkuhn are composed of three types of cells: Goblet cells. Enteroendocrine cells. Pannet cells these cells maintain the mucousal innate immunity by secreting antimicrobial substances. are found in the basal most part and they have a basophilic basal portion which contains zymogens: alpha-defensins an eosinophilic granulated apical part the contains transport vesicles.

Within the lamina propria there are also few Brunner glands. Muscularis mucousa a smooth muscle layer. Submucousa loose C.T that contains a very high amount of mucous secreting glands called Brunner glands. These glands grow so much that they pierce into the muscularis mucousa and enter the lamina propria. As a result, in between the glands there will be smooth muscle remnants (eosinophilic). Brunner glands are characteristic only for the duodenum. The

Brunnner glands secrete an alkaline mucous secretion to buffer the acidic chyme that reaches the proximal part of the small intestine. This higher pH is also optimal to activate digestive enzymes that reach the duodenum.

Muscularis externa composed of two layers: Inner circular. Outer longitudinal.

Sub serousa. Serousa.

Tips: 1. The best way to know which part of the pylorus is shown is by

looking at the epithelium. 2. The pylorus has a very muscular external layer which is the

sphincter itself. 3. In the stomach part of the pylorus, the pyloric glands do not

contain chief cells and parietal cells.

duodenumstomach

Type of tissue: A section of the gastro-duodenal junction. Staining method: PAS + Hematoxylin. With PAS, the

mucous secreting cells are easier to detect.

Special features: 1. In this slide it is much easier to

make the difference between the gastric portion and the duodenal portion of the pylorus.

Special features: 2. The stomach portion of the pylorus:

The surface epithelium is PAS positive it secretes mucous. The pyloric glands are also PAS positive and they are located in the lamina propria.

3. Duodenal part of pylorus: The surface epithel is not stained with PAS because it does not secrete mucous. Goblet cells within the epithelium will be stained in a dark blue/purple color (PAS positive). Goblet cells within the crypts of Leiberkuhn will be stained in a dark blue/purple color (PAS positive). Brunner glands in the submucousa and in the basal part of the lamina propria are also stained in purple- secrete mucous.

4. The basement membrane will be stained purple because it contains reticular fibers that have a high amount of carbohydrates.

Stomach part

Duodenal part

Stomach part

Duodenal part

Type of tissue: A cross section of the jejunum. Staining method: Hematoxylin and Eosin. Special features: 1. The jejunum is composed of:

Epithel. Lamina propria. Muscularis mucousa. Submucousa. Muscularis externa. Sub serousa. Serousa.

2. More into details: Epithel- composed of simple columnar epithelium with brush border and Goblet cells (enterocytes). Lamina propria composed of lymphoreticular C.T as part of the MALT family and some lymphatic follicles can often be seen. In the basal part of the lamina propria the crypts of Leiberkuhn are present. The lamina propria is designed as finger-like protrusions that are called intestinal villi, these villi also have smooth muscles that control motility. Within the villi, plasma cells secrete immunoglobulins (IgA). Submucousa the submucousa consist of protrusions that go into the lamina propria. These are called valves of Kerckeing, they increase the surface area of the small intestine and assist absorption. (the Brunner glands are not present! They are strictly found in the duodenum)

Muscularis externa is composed of two layers: Inner - circular. Outer longitudinal.

Between these two layers of smooth muscle are two nerve plexi of the enteric nervous system:

Myenteric plexus. Submucousal plexus.

3. Cellular population on the surface of the jejunum: Epithelial cells. Goblet cells. M- cells (microfolds) : these cells are found above lymphatic rich areas and they are antigen transporting cells

4. Structures that increase the absorption surface area: Brush border. Intestinal villi. Valve of Kerckring.

5. In the center of the intestinal villi are found lacteals. These are lymph vessels (capillaries) that collect absorbed chylomicrones.

Valve of Kerckeing

mucousa Muscularis externa

Valve of Kerckeing

Crypts of Leiberkuhn

Valve of Kerckeing

Muscularis mucousa Inner circular Outer longitudinal

Lamina propria

enterocytes

Goblet cell

Type of tissue: A cross section of the jejunum and ileum. Staining method:

trichrome. Special features: 1. The jejunum and ileum are

composed of: Epithel. Lamina propria. Muscularis mucousa. Submucousa. Muscularis externa. Sub serousa. Serousa.

2. The bottom line: this slide comes to show us the Panneth cells in the crypts of

Leiberkuhn. The basal part of the cells is dark basophilic and the apical portion contains eosinophilic granules that contain zymogens.

3. All mucous secreting cells in the slide will be stained in light green. 4. Nuclei are stained in dark blue.

Pannet cell

Type of tissue: A longitudinal section of the colon. Staining method: Hematoxylin and Eosin. Special features: 1. The colon is composed of:

Epithel. Lamina propria. Muscularis mucousa. Submucousa. Muscularis externa. Sub serousa. Serousa.

2. More into details: Epithel: simple columnar epithel small amounts of micro villi and goblet cells (enterocytes). Also consist of some M-cells. Lamina propria part of GALT. Contains a lymphoreticular connective tissue. There are no intestinal villi, the elongated coulmnar structures are actually glands (elongated tubular glands) which are elongated crypts of Leiberkuhn. The cell population in these crypts is: goblet cells and entero endocrine cells. (there are no pannet cells.). Also in the lamina propria some lymphatic follicles can be seen. Muscularis externa mostly composed of 2 layers but in some cases it can be seen that the outer longitudinal layer is missing. In that case it is taken between tiniae coli (3 elongated bundles).

Type of tissue: A cross section of the vermiform appendix. Staining method: Hematoxylin and Eosin. Special features: 1. The appendix is composed of:

Epithel. Lamina propria. Muscularis mucousa. Submucousa. Muscularis externa. Sub serousa. Serousa.

2. More into details: Epithel: simple columnar epithel small amounts of micro villi and goblet cells (enterocytes). Also consist of some M-cells. Lamina propria part of GALT. Contains a lymphoreticular connective tissue. Consist of secondary lymphatic follicles. Also contains HEVs. Submucousa can be divided into two parts: the upper portion is occupied by secondary lymphatic follicles and a Lower part that is composed of loose C.T. Muscularis externa mostly composed of 2 layers. There are no tiniae coli (except for the opening from the colon).