L7: Digestive 2

Question 1

Function/organization of the small intestines

Answer 1

Functions: completes digestion, absorbs nutrients, secretes gut hormones

Consists of 3 regions: Duodenum, Jejunum, Ileum (Anterior to Posterior)

Question 2

Plicae

Answer 2

Smal intestines

mucosal folds with submucosal core, act to increase surface area for absorption

Question 3

Villi

Answer 3

= fingerlike mucosal projections with lamina propria core, also increase surface area for absorption

Small intestines

Question 4

Microvilli of cells that make up the villi

Answer 4

smal intestines

fingerlike projections of apical cell membranes, make up “brush border” on epithelial membrane; further increase surface area for absorption

Question 5

Crypts of Lieberkuhn

Answer 5

mucosal glands of intestine, extend downward between villi; produce mucus, enzymes, hormones

Small intestines.

Question 6

Crypts of Lieberkuhn: Paneth Cells

Answer 6

= stain vivid red in H&E

secrete lysosomes that degrade bacteria

proteins and mucopolysaccharides;

also have phagocytic role;

function to regulate intestinal bacterial flora

Question 7

Crypts of Lieberkuhn: Enteroendocrine cells

Answer 7

secrete hormones involved in gastric secretion,

intestinal motility

pancreatic secretion and gall bladder contraction;

same hormones as from enteroendocrine cells in gastric glands

Question 8

Germinative zone of crypts of lieberkuhn

Answer 8

Crypt base columnar cells

serve as stem cells for all other crypt cell types

Question 9

Name the crypts of lieberkuhn celltypes

Answer 9

Paneth cells

enteroendocrine cells

goblet cells

crypt base columnar cells (germinative)

Question 10

Brunner’s glands

Answer 10

submucosal

small intestines

secrete alkaline mucus that protects epithelium by neutralizing acid from stomach

Question 11

Peyer’s patches

Answer 11

large masses of nodules exist in the L. propria of the ileum

lamina propria has numerous lymph nodules which may also extend into submucosa

Question 12

Function of the large intestines

Answer 12

resorbs water from intestinal contents, secretes mucus for lubrication, no digestive enzymes are secreted by the large intestine

Question 13

Component sections of the large intestines

Answer 13

Sections (anterior to posterior) =

Ileocecal valve/cecum (appendix = diverticulum from cecum) → colon → rectum → anus

Question 14

Distinguishing characteristics of the large intestines

Answer 14

crypts are deeper than in small intestines

no plicae or villi present in LI but short microvilli present on lumenal surface

Outer longitudinal layer of muscularis externa is aggregated into 3 longitudinal bands = taenia coli

Question 15

What cells are found in large intestinal crypts?

Answer 15

goblet cells= numerous!! aid passage of mroe solid waste

columnar cells= same as mucosal surface cels

enteroendocrine cells

basal stem cells

Question 16

Describe the appendix.

Answer 16

Diverticulum from anterior part of large intestine

Contains prominent lymphatic nodules in L. propria which extend deep into the submucosa

Structurally similar to LI

Question 17

What are the prominent lymphatic nodules in the appendix for?

Answer 17

These function to combat microbial or parasite antigens from small intestine and from the large intestine where bacterial content is much higher than in other parts of digestive tract.

Question 18

Appendix crypts

Answer 18

Appendix crypts contain a few Paneth cells and goblet cells and numerous enteroendocrine cells

Question 19

General: Digestive Gands

Answer 19

Develop as outgrowths of gut epithelium
Include …

Pancreas

Liver

Gall Bladder

Question 20

Describe the pancreas (general)

Answer 20

Contains exocrine (empties to duodenum) and endocrine portions.

Question 21

Exocrine pancreas secretion (what enzymes does it contain? what shape of gland?)

Answer 21

Exocrine portion: Compound tubuloalveolar gland

Exocrine secretion = alkaline serous secretion containing enzymes that break down proteins (trypsin, chymotrypsinogen, carboxypeptidase), fats (lipase) and carbohydrates (amylase).

The proteolytic enzymes are released as inactive forms that are activated by other enzymes after entering duodenum.

Centroacinar Cells = one or more pale-staining cells in middle of acini, represent terminal cells of intercalated ducts. Distinguish pancreas from salivary glands.

Question 22

Centroacinar cells of exocrine pancreatic ducts

Answer 22

part of the compound tubuloalveolar gland

one or more pale-staining cells in middle of acini, represent terminal cells of intercalated ducts. Distinguish pancreas from salivary glands.

Question 23

Endocrine pancreas secretion (cell types, anatomy)

Answer 23

Endocrine Secretion = Islets of Langerhans (pale-staining spherical regions of polygonal glandular cells in reticular CT, highly vascularized)

Cell types:

Alpha cells

Beta cells

D cells

C Cells

Question 24

Alpha cells of pancreas

Answer 24

20%

found mainly at periphery of islets

have pinkish cytoplasm with Masson trichrome;

secrete glucagon (causes glycogenolysis, lipolysis, gluconeogenesis, thereby increasing blood glucose levels)

Question 25

Beta cells of pancreas

Answer 25

75% of cells

found on interior of islets

produce insulin (causes glycogenesis in liver and skeletal muscle and cellular uptake of glucose which decreases blood glucose)

Question 26

D cells of pancreas

Answer 26

5%

resemble alpha-cells, but larger, bluish cytoplasm with Masson trichrome

secrete somatostatin which inhibits secretion of insulin and glucagon

Question 27

C cells of pancreas

Answer 27

small unstained cells in interior, not present in humans, possibly represent reserve cells

Question 28

Functions of the liver

Answer 28

The largest compound gland (compound tubular) in the body

FUNCTIONS:

Metabolic interconversion and synthesis

Detoxification

Phagocytosis/Waste removal (e.g., bilirubin from Hemoglobin breakdown)

Secretion of bile - contains bilirubin, IgA (Antibody activity, forms immunological barrier against microbes), bile salts (emulsify fats)

Question 29

Liver structure (basic units, components)

Answer 29

Dense irregular CT capsule covered by mesothelium

Divided into lobes, lobes into lobules (4 lobes in humans)

Basic unit of structure = Liver Lobule (hexagonal in shape)

• Central Vein = located at center of lobule (middle of hexagon)
• Sinusoids = thin-walled blood vessels between cords of hepatocytes
• Portal Canal = contains portal vein, hepatic artery, bile duct, lymphatic, nerve
• Hepatocytes = epithelial secretory cells, secrete bile, stacked into cords radiating outward from central vein

Question 30

pathway of bile

Answer 30

Bile secreted from hepatocytes into bile canaliculi → bile ductules → bile duct → hepatic duct → common bile duct (empties to duodenum)

Question 31

Liver sinusoids supplied by..

Answer 31

venules from portal canal capillaries (empty to hepatic artery) and from portal vein

Question 32

Hepatocytes

Answer 32

epithelial secretory cells, secrete bile

stacked into cords radiating outward from central vein

When bordering sinusoids, have microvilli (increase SA for absorption and secretion)

those project into space of disse

Question 33

Space of disse

Answer 33

in liver; hepatocyte microvilli project here.

microvilli project into this space between hepatocytes and sinusoidal endothelium (no basal lamina present)

Question 34

What are the liver sinusoids lined by?

Answer 34

Endothelial Cells = squamous cells forming fenestrated membrane (gaps exist between cells)

Kupffer Cells = fixed macrophages, look similar to monocyte (although usually more elongate)

Question 35

Describe the gall bladder (how and when it functions)

Answer 35

Thin-walled elongate sac, stores and concentrates bile

Mucosa when empty is highly folded, tall columnar epithelium

No muscularis mucosae or submucosa

Drained by cystic duct, joins hepatic duct to form common bile duct

Following a meal, gall bladder stimulated to contract by duodenal hormones and parasympathetic stimulation of Sphincter of Oddi (surrounds entrance of common bile duct into duodenum)

Bile enters gall bladder by backing up from hepatic duct up through the cystic duct