Chapter 24 - Digestive System

Question 1

Functions of Digestive System

Answer 1

1. ingestion - intake of food
2. digestion - mechanical and chemical breakdown
3. absorption - uptake of nutrients
4. compaction - absorption of water, consolidation of indigestible residue
5. defecation - elimination of feces

Question 2

Alimentary Canal

Answer 2

mouth through anus

Question 3

Gastrointestinal (GI) Tract

Answer 3

stomach and intestines

Question 4

Enteric Nervous System

Answer 4

• nervous network exclusive to the esophagus, stomach, and intestines
• submucosal plexus (submucosa) - controls movements of the muscularis mucosae and glandular secretions
• myenteric plexus (between layers of the muscularis externa) - controls peristalsis and other contractions of the muscularis externa

Question 5

Accessory Organs of the Digestive System

Answer 5

• teeth
• tongue
• salivary glands
• liver
• gall bladder
• pancreas

Question 6

General Histology

Answer 6

• Mucosa
  
  • Epithelium
  • Lamina propria (loose connective tissue)
  • Muscularis mucosae (smooth muscle)
• Submucosa (loose connective tissue with vessels and nerves)
• Muscularis Externa (smooth muscle for propulsion and mixing, inner circular layer & outer longitudinal layer)
• Serosa or Adventitia (areolar tissue topped with simple squamous mesothelium)

Question 7

Mesenteries

Answer 7

connective tissue sheets holding abdominal viscera in place

Question 8

Posterior and Anterior Messenteries

Answer 8

two-layered membrane that may hang freely or connect organs together or to abdominal wall

Question 9

Lesser Omentum

Answer 9

messentery, extend from lesser curvature of stomach to liver

Question 10

Greater Omentum

Answer 10

messentery, hangs down like an apron from stomach’s greater curvature

Question 11

Mesocolon

Answer 11

messentery of the colon

Question 12

Mouth

Answer 12

• oral (buccal) cavity
• oral fissure to fauces
• cheeks and lips
  
  • labial frenulum - median fold attaching lip to gum
  • vestibule - space just inside lips and cheeks
• palate
  
  • hard (bony)
  • soft - include uvula

Question 13

Tongue

Answer 13

• lingual papillae (vallate, foliate, fungiform)
• body - anterior 2/3
• root - posterior 1/3
• lingual frenulum - attachment to floor of mouth

Question 14

Teeth

Answer 14

• “Dentition”
• incisors - chisels
• canines - puncture and shred
• premolars and molars - crush and grind
• 20 deciduous vs. 32 permanent
• embedded in mandible and maxilla
  
  • alveolus - socket
  • periodontal ligament
  • cementum of root
• gingiva surrounds neck
• internal structures
  
  • dentin
  • pulp cavity, root canal (spaces for nerves and vessels)

Question 15

Salivary Glands

Answer 15

1. parotid - near ear
2. sumandibular - under jaw
3. sublingual - under tongue
   - tubuloacinar structure
   - mucous and serous cells
   - saliva contains:
   
   • amylase and lipase
   • mucus
   • lysozyme
   • immunoglobulin A
   • electrolytes

Question 16

Pharynx and Esophagus

Answer 16

• oropharynx and laryngopharynx pass food
  
  • walls contain skeletal muscle
  • nonkeratinized stratified squamous epithelium
• esophagus is posterior to trachea
  
  • starts behind larynx
  • passes through esophageal hiatus of diaphragm
  • ends at lower esophageal sphincter located at the cardiac orifice to stomach
• digultation = swallowing, coordinated by swallowing center of medulla

Question 17

Microscopic Anatomy of the Stomach

Answer 17

• gastric pits of mucous with glands
  
  • mucous cells - mucus
  • regenerative cells - new cells
  • parietal cells - HCl, intrinsic factor, Ghrelin
  • chief cells - pepsinogen, gastric lipase
  • enteroendocrine cells - hormones, gastrin

Question 18

Duodenum

Answer 18

• first 10in. of small intestine
• receives and mixes stomach contents, pancreatic juice, and bile
• major duodenal papilla for bile and pancreatic ducts
• minor duodenal papilla for accessory pancreatic duct
• Brunner’s (duodenal/submucosal) glands with bicarbonate rich mucous

Question 19

Jejunum

Answer 19

• 8ft. middle portion of small intestines
• mostly within umbilical region
• most digestion and absorption occur here
• circular folds (plicae circulares)

Question 20

Ilieum

Answer 20

• 13ft distal portion of small intestitnes
• sparse folds, pink color
• Peyer patches - lymphatic nodules
• ileocecal junction, ileocecal valve

Question 21

Microscopic Anatomy of Small Intestine

Answer 21

• villi
  
  • enterocytes (absorptive cells) have tiny microvilli projections
  • goblet cells
  • lacteals - lymphatics for lipid absorption
• intestinal crypts - goblet cells and absorptive cells
  
  • Paneth cells - enteroendocrine; secrete lysozyme

Question 22

Microscopic Anatomy of Large Intestine

Answer 22

• mostly simple columnar, except anus (nonkeratinized stratified squamous epithelium)
• has intestinal crypts but no villi or circular folds
• abundant lymphatic tissue
• mucosa specialized for fluid and electrolyte absorption

Question 23

Liver

Answer 23

• body’s largest gland
• over 200 functions
  
  • hematological, metabolic, storage, immunity
  • digestive function is bile production
    
    • bilirubin - decomposition of hemoglobin
    • urobilogen - metabolized bilirubin (feces brown)
    • bile acids/lecithin - emulsify fats

Question 24

Microscopic Anatomy of the Liver

Answer 24

• hepatic lobules - small cylinders w/ central vein, radiating plates of hepatocytes
  
  • hepatic sinusoids - leaky capillaries
  • hepatic macrophages - (Kupffer cells) clean blood
  • bile canaliculi -> bile ductules -> right/left hepatic ducts

Question 25

Liver Circulation

Answer 25

- hepatic portal vein - brings nutrient rich blood from veins of GI tract to liver - hepatic artery * brings arterial blood to liver * aorta -> celiac truck -> common hepatic a. -> hepatic artery proper -> hepatic a. - hepatic veins - exit from top of liver and empty into inferior vena cava

Question 26

Gallbladder

Answer 26

- sac on underside of liver - stores and concentrates bile - fundus (head), cervix (neck) - cystic duct

Question 27

Bile Passages

Answer 27

- two hepatic ducts merge -> common hepatic duct - common hepatic duct + cystic duct (from gallbladder) -> bile duct - bile duct + pancreatic duct -> hepatopancreatic ampulla at major duodenal papilla

Question 28

Pancreas

Answer 28

- retroperitoneal - posterior to stomach - head (near duodenum), tail (near spleen) - endocrine islets secrete insulin and glucagon - mostly exocrine tissue secreting pancreatic juice * enzymes, zymogens (inactive precursors of enzymes), sodium bicarbonate, water, and electrolytes - branching ducts * pancreatic duct * accessory pancreatic duct - opens at minor duodenal papilla - acinar cells (exocrine)