Practicals Nr. 3: digestive system (III) 17. Intestinum crassum (HE) 18. Appendix (HE) 19. Anus (HE) 20. Hepar (HE) 21. Hepar (Azan) 22. Vesica fellea (HE) 23. Pancreas (HE)

– Atlas EM:Liver cells – hepatocytes, bile canaliculus – bile capilary (10, 13, 14, 17, 20)

Processus vermiformis, appendix (Homo)(cross section, HE)

A. Tunica mucosa – intestinal villi are missing, crypts of Lieberkühn are shallow and irregular:1. lamina epithelialis mucosae – simple collumnar epithelium composed of enterocytes, goblet

cells and enteroendocrine cells,2. lamina propria mucosae – reticular connective tissue with numerous active lymphatic nodules,3. lamina muscularis mucosae – usually is missing or irregular.

B. Tela submucosa – loose connective tissue with vesssels and nerves.C. Tunica muscularis (externa) – thin layers of smooth muscle tissue (circular and longitudinal

layer).D. Tunica serosa - mesothelium and thin layer of collagenous connective tissue.

The serosa.

Intestinum crassum (Homo) (longitudinal section through the wall, HE)

Plicae semicirculares Kerckringi and intestinal villi are NOT present – luminal surface is smooth.A. Tunica mucosa:

1. lamina epithelialis mucosae – tall columnar epithelium consists of absorptive cells – enterocytes,

2. lamina propria mucosae – reticular connective tissue with lymphatic nodules; crypts of Lieberkühn are deep and numerous, they are lined with the same epithelium (ad 1.); except enterocytes, numerous goblet cells and some enteroendocrine cells (are not visible in LM) are present in the epithelium,

3. lamina muscularis mucosae – smooth muscle tissue.B. Tela submucosa – loose connective tissue with blood vessels and nerves (plexus submucosus

Meissneri).C. Tunica muscularis (externa) – two layers of smooth muscle cells bundles – inner circular and

outer longitudinal (nerve – plexus myentericus Auerbachi in connective tissue between them). D. Tunica serosa (see practice nr. 2).

Anus (Homo) (longitudinal section through the wall, HE)

- is a part of rectum and is divided into 3 zones: zona haemorhodalis, zona intermedia, zona cutanea; structure of the wall shows regional differences (see table)

Hemorhoidal zone Intermedial zone Cutaneous (skin) zone

Mucosa:

- simple columnar ep.- lamina propria is

reticular c.t.- lamina muscularis

Submucosa

External muscle coat –

smooth muscle tissue

Adventitia

Mucosa:

- stratified squamous ep.

- lamina propria is areolar c.t.

- lamina muscularis NOSubmucosa

External muscle coat –

smooth inner sphincter

Adventitia

Skin:

- epidermis- dermis with skin

adnexa amd pigment cells

External muscle coat –

skeletal external sphincter

Adventitia

Hepar (Homo)(Hematoxylin-eosin or Azan)

A. Liver connective tissue (c.t.):

1. capsula fibrosa hepatis – dense collagenous c.t. (it is present only in some slides),2. c.t. in portal areas – loose c.t.; portal area has triangular shape and is surrounded by 3 – 4

morphological units = liver lobules of central vein; c.t. of portal area carries interlobular brunches of a.hepatica, v.portae and interlobular bile duct,

3. interlobular c.t. – separates liver lobules in the rest of their surface (outside the portal areas), only minimum of this c.t. is in human liver.

pig liver human liver

B. Liver parenchyma – consists of morphological units = lobules of central vein (liver lobules) and intrahepatic bile ducts: 1. lobules of central vein – five to six–sided polyhedral prisms in the sections, composed of

plates (cords in the sections) of hepatocytes; plates (cords) are organized radialy around v. centralis:– hepatic plates – consist of 1 - 2 lines of hepatocytes, which surround bile canaliculi (are

not visible in the sections),– liver sinusoids – are situated between plates, have an irregular width of the lumen, and are

lined with endothelium; Kupffer cells are present in the regions where the sinusids are branched,

– vena centralis – thinwalled vein in the center of the lobule (endothelium and thin layer of loose c.t.),

Functional unit: portal lobule (lobule of portal vein) – parts of parenchyma of 3 morphological units surrounding

common portal area (triangular region with portal area in the center – join central veins of 3 nighbour liver lobules)

smaller unit is liver acinus – parencyma of 2 liver lobules arround common circumlobular side.

2. intrahepatic bile ducts:– canals of Herring – continue bile canaliculi and are lined with simple cuboid epithelium

(canals are located at the periphery of the lobules).– interlobular bile ducts – simple cuboid to columnar epithelium – in portal areas.– lobar bile ducts – are two; their wall consists of tall columnar epithelium, lamina basalis

and a layer of c.t. (are not found in the slides).

Pancreas (Homo)(Hematoxylin - eosin)

A. Connective tissue (c.t.):1. dense collagenous c.t. of capsule and septa, which carry blood vessels and interlobular ducts,

septa separate gland into the lobules,2. loose c.t. inside of lobules (intralobular c.t.).

B. Parenchyma – lobules; each of them contains elongated serous acini (exocrine part of gland), intralobular ducts and one or more islet(s) of Langerhans (endocrine part of gland without ducts):1. serous acini:

– serous cells – triangular or pyramid shape, nucleus at the basis of the cell, secretory granules in supranuklear zone of cytoplasm (granules stain intensely),

– centroacinar cells – polygonal shape, pale cytoplasm; cells are situated only in the center of acinus,

2. ducts – intercalated and interlobular:– intercalated – simple squamous epithelium, narrow lumen (identification is dificult),– intralobular ducts – arrise by fusion of intercalated ducts, simple cuboid epithelium

(epithelial cells without basal straition – they have not basal labyrinth),3. islets of Langerhans:

– fine capsule (with fine collagen and reticular fibers) separates the islet from acini,– cord of glandular endocrine cells – cells are polyhedral and pale (the main identifying

sign); blood sinusoids form a network around cords of the cells.Notice: endocrine celss is not possible to classify in HE slides.

Vesica fellea (Homo) (Hematoxylin - eosin)

A. Tunica mucosa: numerous mucosal folds1. lamina epithelialis mucosae – tall columnar epithelium (produce mucus),

2. lamina propria mucosae – reticular connective tissue with lymphatic nodules; crypts of Lieberkühn are deep and numerous, they are lined with the same epithelium (ad 1.); except enterocytes, numerous goblet cells and some enteroendocrine cells (are not visible in LM) are present in the epithelium,

lamina muscularis mucosae – is NOT present.B. Tela submucosa – is NOT present.C. Tunica muscularis (externa) –smooth muscle tissue (longitudinal and oblique orientation). D. Tunica serosa – covers free surface of gall bladder and has very thick layer of subserosal c.t.;

the surface turned to the liver tissue is covered with adventitia.