Exam 4

Question 1

Describe the four layers of alimentary canal walls (mucosa, submucosa, smooth muscle,
serosa), including the histological composition of each layer (epithelium, lamina propria,
muscularis mucosa, connective tissue, smooth muscle).

Answer 1

Lumen
* Mucosa
epithelium: type depends on location
lamina propria: conn. tissue with MALT (mucosa-associated lymphoid tissue)
muscularis mucosae: thin layer of smooth muscle
stomach only rugae

• Submucosa (connective tissue with vessels, nerves, lymphatics)
• Muscularis externa (smooth muscle)
  circular layer: lumen diameter
  longitudinal layer
  stomach only oblique layer: helps food breakdown
• intraperitoneal: Serosa
  simple squamous epithelium AND conn. tissue
• retroperitoneal: Adventitia
  (esophagus)
  ONLY connective

Question 2

Describe the histological composition of individual GI organs (oral cavity, esophagus, stomach,
small intestine, large intestine) in terms of epithelium (stratified squamous or simple
columnar), specialized cells (goblet cells, enterocytes), and notable features (gastric glands,
gastric pits, lacteals, villi, microvilli, Brunner glands, Peyer patches).

Answer 2

• oral cavity ingestion, make moisture/enzymes via non-keratinized stratified squamous epithelium
• esophagus transfer food bolus via non-keratinized stratified squamous epithelium and mucus secretion viagoblet cells
• stomach mechanical breakdown via oblique layer and enzymatic breakdown via simple columnar epithelium, expands via rugae in mucosa
  gastric pits in mucosa are depressions that open into gastric glands in the lamina propia (secretion)
• small intestine enzymatic digestion via mucus-secreting goblet cells and nutrient absorption via enterocytes, which havevili projections to increase SA, contain lacteals for vessels/lymph channels
  Microvilli (brush border) are smaller projections directly from enterocytes
  simple columnar epithelium

1st part of SI= Duodenum
Brunner glands secret bicarb for gastric acid neutralization

2nd part= jejunum

3rd part= ileum
many goblet cells (mucus) and Peyer patches (lymphoid tissue)

• Colon (large intestine) water and electrolyte absorption via simple columnar epithelium with many enterocytes (absorption) and goblet cells (mucus)

Question 3

Describe blood flow through the liver as it enters via either the hepatic artery or hepatic portal vein, moves through a hepatic lobule, and is ultimately returned to the heart.

Answer 3

Hepatic a. / portal v.
hepatic arteriole / venule
sinusoid
central vein
hepatic veins
inferior vena cava

Question 4

Identify the major histological components of a hepatic lobule and describe each component’s
function (hepatic arteriole, hepatic venule, bile duct, central vein, hepatocyte, sinusoid, space
of Disse).

Answer 4

3 bile duct collects bile that is channeled from liver cells via canaliculi

• hepatocytes liver cells
• hepatic lobule is a structural unit of the liver with hepatic portal triad in the corner
  #1 hepatic arterioles carry ox blood hepatic artery -> liver cells
  #2 hepatic venules carry deox blood from GI-> hepatic portal vein-> liver cells

blood from hep a. and v. mixes in sinusoids, which has large gaps b/w endothelial cells
Space of Disse describes space b/w sinusoid lumen and liver cells (filtrate may interact w/ liver cells)

blood from sinusoids collected in central vein and drains into inferior vena cava

Question 5

Describe the path bile takes from a its generation in the hepatocyte, to its storage of secretion through the biliary system.

Answer 5

hepatocyte
canaliculi
bile ducts
biliary system