GASTRO – INTESTINAL TRACT SYSTEM

SCHOOL OF ANATOMICAL SCIENCES

Gastric gland diagramThis longitudinal section through a gastric gland illustrates the distribution of the five cell types in the epithelial lining. Undifferentiated “stem” cells, found in the neck of the gland are not shown here. NOTE:

• The three regions of the gland and its narrow lumen.

• The opening of the narrow lumen into a gastric pit.

• The simple columnar mucus-secreting cells in the epithelium of the stomach.

QuestionsWhat is the significance of undifferentiated “stem” cells in the epithelium of a gastric gland?

What type of gland is this?

How do the glands differ in the different regions of the stomach (cardia, fundus/body and pylorus)?

Chief cell diagramChief cells are protein-producing (serous) cells. NOTE:

• The pyramidal shape (wide base and narrower apex).

• The basal “ergastoplasm” (rough endoplasmic reticulum – rER).

• The spherical nucleus towards the base of the cell.

• The supranuclear Golgi complex.

• The numerous zymogen granules in the apical cytoplasm.

QuestionsWhat are the functions of the rER and Golgi complex in a chief cell?

What do “zymogen” granules contain in a chief cell and why are they called “zymogen”?

What is the significance of heterochromatin in a serous cell nucleus?

Compare with the EMG of chief cells.

Chief cellsSeveral chief cells around the small lumen of a gastric gland are shown here. NOTE:

• The pyramidal shape of the cells.

• The closely packed cisternae of rER in the basal cytoplasm.

• The euchromatin and characteristic heterochromatin in the nucleus.

• The numerous pale-stained zymogen granules in the apical cytoplasm.

QuestionsHow does the secretion from these cells reach the lumen of the stomach?

How do these cells stain in a routine H & E section? (See slide 81)

Explain this staining reaction.

Compare with the diagram of chief cells.

Parietal (oxyntic) cell diagramNOTE:

• The large centrally-located spherical nucleus.

• The intracellular tubulocanalicular system.

• The numerous mitochondria.

QuestionsBriefly explain how hydrochloric acid (HCl) is produced and secreted by the parietal cell.

What is the functional significance of the numerous mitochondria?

What is the function of the basal folds?

Compare with the EMG of parietal cells.

Parietal (oxyntic) cellsNOTE:

• The large centrally-located spherical nucleus (N).

• The intracellular tubules (Tu) and canaliculi (Ca).

• The numerous mitochondria (M).

• The lysosomes (Ly).

• The basal plasma membrane folds (*).

QuestionsWhat are the distinguishing features of a parietal cell?

How can parietal cells be distinguished in an H & E section? (see slide 81)

Compare with the diagram of parietal cells

Small intestineThis EMG shows the epithelial lining of the small intestine. NOTE:

• The brush border (Mv) lining the lumen with the underlying terminal web.

• The spherical mitochondria (M) and lipid droplets (L) in the cytoplasm.

• The mucus secretory granules (MD) in the cytoplasm of the goblet cell.

• The oval vesiciular nuclei with prominent nucleoli towards the base of the columnar cells.

• The basement membrane (BM) with underlying lamina propria.

• The nerve fibres (NF), collagen fibres (Co), capillaries (Cp) and smooth muscle (SM) in the lamina propria.

QuestionsIdentify the epithelium.

Give an example of where this epithelium is found.

Identify the components in the lamina propria, i. e. F, Co, Cp, SM, NF.

What is the function of the “Mv”?

PancreasSeveral pancreatic acinar cells are indicated. NOTE:

• The pyramidal shape of the cells with many mitochondria (M).

• The closely packed cisternae of rough endoplasmic reticulum (ER), magnified in the inset (60 000) to show ribosomes (R).

• The euchromatin and characteristic heterochromatin in the vesicular nucleus (N) with a prominent nucleolus.

• The numerous darkly-stained zymogen granules (Z) and stacks of Golgi apparatus (G) in the apical cytoplasm.

• The nucleus (N) of a centroacinar cell in the lumen (bottom right).

QuestionsWhat do the zymogen granules contain?

What are the functions of the other organelles in this cells?

LiverTwo adjacent hepatocytes are shown here. NOTE:

• The microvilli (Mv) of the hepatocyte projecting into the bile canaliculus (BC).

• The stacked membranes of the smooth (SER), rough endoplasmic reticulum (ER) and Golgi apparatus (G).

• The variable shape of the many mitochondria (M) with extensive cristae (Cr).

• The large spherical lysosomes (Ly) and dark granules and rosettes of glycogen in the cytoplasm.

QuestionHow do the different organelles of the hepatocyte correlate with its function?

LiverIn this EMG of a hepatocyte, NOTE:

• The microvilli (Mv) of the hepatocyte projecting into the sinusoid (Sn) which is lined by endothelium (En) and contains electron dense erythrocytes.

• The space of Disse (*) between the hepatocyte and endothelial lining.

• Endoplasmic reticulum (ER) and Golgi apparatus (G).

• The variable shape of the many mitochondria (M) with extensive cristae.

• The large spherical lysosomes (Ly) and dark granules and rosettes of glycogen (Gl) in the cytoplasm.

• The large oval vesicular nucleus (N) with a prominent nucleolus.

• The microvilli of the hepatocyte projecting into the bile canaliculus (BC).

QuestionsWhat is the function of the bile canaliculus?

Where does the blood in the sinusoid come from?

What does it contain?

How does the hepatocyte change/affect the blood in the