The digestive system

Question 1

Organs of the Gastrointestinal tract: Mouth(oral cavity)

Answer 1

-lined with stratified squamous epithelium
A). teeth: organs of mastication, 20 deciduous, and 32 permanent

B). Tongue:

• skeletal muscle serving in speech, mastication, swallowing, and taste.
• restrained by the lingual frenulumC). Salivary Glands:
• saliva for lubrication and preliminary carbohydrate digestion
• paratod: duct entry lateral to the upper second molar
• submandibular: ducts emerge along both sides of the lingual frenulum
• sublingual: ducts open into floor of mouth

Question 2

Organs of the Gastrointestinal tract: Oropharynx

Answer 2

guarded bilaterally with Palatine tonsils

Question 3

Organs of the Gastrointestinal tract: Esophagus

Answer 3

1. stratified squamous epithelium
   2 food conduction tube posterior to the trachea
2. 1/3 voluntary and 2/3 involuntary(smooth muscle)
3. initiates peristalsis (wavic contraction along a tube)

Question 4

Organs of the Gastrointestinal tract: stomach

Answer 4

• simple columnar epithelium
• food storage organ
• entrance at lower esophageal sphincter
• exit at pyloric sphincter
• “rugae”: internal folds of mucosa
• gastric glands—>HCl and enzymes for protein digestion

Question 5

Organs of the Gastrointestinal tract: small intestine

Answer 5

• site of most digestion and absorption
• duodenum
• jejunum }
• ileum } suspended by mesentery from dorsal body wall

Question 6

Microanatomy of the small intestine:

Answer 6

1. plicae circularis:
   
   • circular folds, increasing surface area
2. villi:
   
   • vascular projections from the tunica mucosa
3. intestinal glands:
   
   • secrete digestive enzymes
4. goblet cells:
   - secrete mucus to protect epithelial cells
5. tunica mucosa:
   
   • simple columnar epithelium
   • lamina propria: underlying connective tissue with blood capillaries and lacteals.
   • muscularis mucosa: smooth muscle
6. tunica submucosa (areolar connective tissue):
   
   • longitudinal group of vessels, nerves, lymphatics)
7. tunica muscularis (smooth muscle):
   
   • contributes to Gi peristalsis
   • circular layer
   • longitudinal layer
8. tunica serous (simple squamous and connective tissue)

Question 7

Organs of the Gastrointestinal tract: Large intestines

Answer 7

• site for absorption of water, vitamins, and minerals
  1. proximal colon:
  
  • cecum: recieves material via the ileocecal sphincter associated with the vermiform appendix
    
    2. distal colon
  • ascending—-> transverse
  • sigmoid

Question 8

Rectum and Anal Canal

Answer 8

• organ for defecation
• lined with stratified squamous epithelium

Anus:

• internal sphincter (smooth muscle)
• external sphincter (skeletal muscle)

Question 9

Digestive processes and related organs

Answer 9

-peritoneum: serous membrane lining the abdominal cavity and digestive organs
1. functions: g.i. support, lubrication, and containment
2. layers:
-parietal: lines abdominal walls
-visceral: extends between and covers organs
3. Subparts:
A). Mesentary:
-fan-shaped, double layer of visceral peritoneum
-encircles jejunum/ileum and anchors them to the dorsal body wall
- acts as a surface for blood vessel conduction
- prevents entanglement
B). Greater omentum:
-apron shaped, quadruple layer of visceral peritoneum
-extends between stomach and transverse colon
- serves in fat deposition and lubrication
C). Lesser omentum:
-two layer sheet of visceral peritoneum
-extends between liver and stomach
-encloses bile duct, hepatic artery and portal vein
D). Mesocolon

Question 10

Digestive functions of liver

Answer 10

1. bile production for fat digestion
2. storage of some fat, fat- soluble vitamins and iron
3. removal and storage of glucose as received via portal circulation
4. interconversion of nutrients (e.g. carbs to fat)

Question 11

Structure of liver:

Answer 11

• attached to the diaphragm by falciform ligament
• four lobes: right, left, caudate (posterior), quadrate (inferior)
• round ligament=former umbilical vein of fetus
  1. gallbladder:
  
  • reservoir for bile production in the liver
  • receives bile via hepatic and cystic ducts
  • drains via cystic and common bile duct into the duodenum via the hepatopancreatic papilla

Question 12

Pancreas:

Answer 12

1. Digestive functions:
   
   • exocrine secretion of digestive enzymes
   • insulin
2. structure:
   
   • attached to inner curvature of duodenum
   • 4 to 8” long; hammer shaped
   • multiple internal ducts lead to hepatopancreatic papilla

Question 13

Digestive processes

Answer 13

1. Ingestion:
   -mastication, mechanical breakdown by teeth/ tongue
2. digestion:
   -molecular breakdown of carbohydrates and proteins by enzymes from salivary glands, stomach, pancreas, and duodenum
   -molecular breakdown of fats by enzymes from pancreas and bile from the liver
3. absorption:
   
   • movement of molecules into circulatory or lymphatic systems
   • transported into the capillaries of the small intestine
     epithelial cells of villi—>lacteals—>lymphatic vessels in submucosa—> thoracic duct—> left subclavian vein
4. defecation
   -elimination of feces: dietary fiber (non -digestible food), sloughed intestinal cells and bacteria.