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Anatomy and physiology-Degree > Digestive system > Flashcards

Digestive system Flashcards

1
Q

what is the Digestive tract also called?

A

alimentary tract or canal

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2
Q

what are some of the parts of the Digestive tract and accessory organs?

A

◦ Tube from oral cavity to
anus
◦ GI tract: refers to
stomach and intestines

 Accessory organs
◦ Primarily glands, secrete fluids into tract

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3
Q

what are the functions of the digestive tract? part 1

A
  1. Ingestion: introduction of food into stomach
  2. Mastication: chewing
    ◦ Increases surface area
  3. Propulsion
    ◦ Deglutition: swallowing
    ◦ Peristalsis: moves material through digestive tract
  4. Mixing – contractions to increases contact with enzymes
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4
Q

what are the functions of the digestive tract? part 2

A
  1. Secretion: lubricate, liquify, digest
    ◦ Mucus: secreted along entire digestive tract, lubricates food and lining, protects from mechanical digestion, acid and digestive enzymes
    ◦ Water: makes food easier to digest and absorb
    ◦ Bile: emulsifies fats
    ◦ Enzymes: chemical digestion
  2. Digestion: Mechanical and chemical
  3. Absorption: Movement from tract into circulation or lymph
  4. Elimination: Waste products removed from body;
    Defecation
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5
Q

what is the Histology of the digestive tract-Mucosa?

A

Mucosa. Innermost layer, consisting of:

  1. Mucous epithelium
  2. Lamina propria: loose C.T.
  3. Muscularis mucosae: smooth muscle.

• Mucosa extends into lamina propria in places to
form intestinal glands or crypts.

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6
Q

what is the Histology of the digestive tract-Submucosa?

A

Thick C.T. layer with nerves,

blood vessels, small glands. Parasympathetic submucosal plexus.

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7
Q

what is the Histology of the digestive tract-Muscularis?

A

2 or 3 layers of smooth muscle, including circular and longitudinal layers.

Muscularis contains the myenteric plexus between circular and longitudinal layers. Plexus controls movements along GI tract.

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8
Q

what is the Histology of the digestive tract-Serosa or adventitia?

A

Connective tissue.

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9
Q

regulation of the Digestive system-Nervous system?

A

• Local: enteric nervous system
◦ Coordinates peristalsis and
regulates local reflexes

• General: coordination with the CNS.
◦ May initiate reflexes because of sight, smell, or taste of food.
◦ Primarily parasympathetic

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10
Q

regulation of the Digestive system-Chemical system?

A

• Production of hormones
– Gastrin, secretin

• Production of paracrine
chemicals like histamine

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11
Q

Saliva and its function

A

• Compound alveolar salivary glands produce saliva

◦ Prevents bacterial infection
◦ Lubrication
◦ Contains salivary amylase that breaks down
◦ Helps to form bolus for swallowing
◦ Parasympathetic input causes salivary production

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12
Q

stomach and its openings

A

◦ Gastroesophageal: from oesophagus

◦ Pyloric: to duodenum

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13
Q

what is the first stage of the Cephalic phase?

A

The taste, smell, or thought of food or tactile sensations of food in the mouth stimulates oblongata

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14
Q

what is the second stage of the Cephalic phase?

A

Vagus nerves carry parasympathetic action potentials to the stomach, where enteric plexus neurons are activated.

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15
Q

what is the third stage of the Cephalic phase?

A

Postganglionic neurons stimulate secretion by parietal and chief cells and stimulate gastrin and histamine secretion by endocrine cells

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16
Q

what is the fourth stage of the Cephalic phase?

A

Gastrin is carried through the circulation back to the stomach, where, along with histamine, it stimulates secretion

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17
Q

what is the first stage of the Gastric phase?

A

Distention of the stomach stimulates mechanoreceptors and activates a parasympathetic reflex. Action potentials generated by the mechanoreceptors are carried by the vagus nerves to the medulla oblongata

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18
Q

what is the second stage of the Gastric phase?

A

The medulla oblongata increases action potentials in the vagus nerves that stimulate secretions by parietal and chief cells and stimulate gastrin and histamine secretion by endocrine cells

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19
Q

what is the third stage of the Gastric phase?

A

Distention of the stomach also activates local reflexes that increase stomach secretions

20
Q

what is the fourth stage of the Gastric phase?

A

Gastrin is carried through the circulation back to the stomach, where, along with histamine, it stimulates secretion.

21
Q

what is the first stage of the Intestinal phase?

A

Chyme in the duodenum with a pH less than 2 or containing fat digestion products 9 lipids) inhibits gastric secretion by three mechanisms (2-4)

22
Q

what is the second stage of the Intestinal phase?

A

chemoreceptors in the duodenum are stimulated by H+ (low pH) or lipids. Action potentials generated by the chemoreceptors are carried by the vagus nerves to the medulla oblongata, where the inhibit parasympathetic action potentials, thereby decreasing gastric secretion

23
Q

what is the third stage of the Intestinal phase?

A

local reflexes activated by H+ or lipids also inhibit gastric secretion

24
Q

what is the fourth stage of the Intestinal phase?

A

secretin and cholecystokinin produced by the duodenum decrease gastric secretions in the stomach.

25
Q

small intestine characteristics and divisions

A

• Site of greatest amount of
digestion and absorption
of nutrients and water

• Divisions:
◦ Duodenum- first 25 cm
◦ Jejunum- 2.5 m
◦ Ileum- 3.5 m

26
Q

Small intestine-Duodenum

A

• Curves to the left; head

of pancreas in the curve

27
Q

what are the modifications to increase surface area of the small intestine?

A 
• Increase surface
area 600 fold:
̶ Plicae circulares
̶ Villi
̶ Microvilli
28
Q

small-intestine-Jejunum and Ileum

A

• Similar in structure to the duodenum

  • Gradual decrease in:
  • Diameter
  • Thickness of intestinal walls
  • Number of circular folds
  • Number of villi

• Duodenum and Jejunum are the major site of nutrient
absorption

29
Q

what is the first stage of the Liver, Gallbladder, Pancreas and Ducts?

A

The hepatic ducts, which carry bile from the liver lobes, combine to form the common hepatic duct.

30
Q

what is the second stage of the Liver, Gallbladder, Pancreas and Ducts?

A

The common hepatic duct combines with the cystic duct from the gallbladder to form the common bile duct.

31
Q

what is the third stage of the Liver, Gallbladder, Pancreas and Ducts?

A

The common bile duct and the pancreatic duct combine to form the hepatopancreatic ampulla

32
Q

what is the fourth stage of the Liver, Gallbladder, Pancreas and Ducts?

A

The hepatopancreatic ampulla empties bile and pancreatic secretions into the duodenum at the major duodenal papilla

33
Q

what is the fifth stage of the Liver, Gallbladder, Pancreas and Ducts?

A

The accessory pancreatic duct empties pancreatic secretions into the duodenum at the minor duodenal papilla

34
Q

what are the functions of the liver? part 1

A

• Bile production: 600-1000 mL/day. Bile salts,
cholesterol, fats, fat-soluble hormones, lecithin

◦ Neutralizes and dilutes stomach acid

◦ Bile salts emulsify fats. Most are reabsorbed in the ileum.

◦ Secretin (from the duodenum) stimulates bile secretions, increasing water and bicarbonate ion content of the bile

• Storage
◦ Glycogen, fat, vitamins, copper and iron. Hepatic portal blood comes to liver from small intestine.

35
Q

what are the functions of the liver? part 2

A

• Nutrient interconversion

• Detoxification
◦ Hepatocytes remove ammonia and convert to urea

• Phagocytosis

• Synthesis
◦ Albumins, fibrinogen, globulins, heparin, clotting factors

36
Q

Pancreas-Endocrine and Exocrine

A
  • Pancreas both endocrine and exocrine
  • Endocrine: pancreatic islets. Produce insulin, glucose, and somatostatin
  • Exocrine: grape-like clusters form lobules separated by septa.
37
Q

Large intestine characteristics and what does it consist of?

A

• Consists of cecum, colon, rectum, anal canal

• Movements sluggish (18-24 hrs); chyme
converted to faeces.

• 90% of volume of chyme is reabsorbed in the
large intestine

38
Q

Anatomy of the large intestine?

A

 Cecum
◦ Blind sac, appendix attached.

 Colon
◦ Ascending - transverse
◦ Descending - sigmoid

 Rectum
◦ Straight muscular tube,
thick muscular tunic

 Anal canal
◦ Internal anal sphincter (smooth muscle)
◦ External anal sphincter (skeletal muscle)

39
Q

Digestion and absorption- Digestion function

A

• Digestion
◦ Breakdown of food molecules for absorption into circulation

• Mechanical: breaks large food particles to small

• Chemical: breaking of covalent bonds by digestive
enzymes

40
Q

Digestion and absorption- absorption and transport function

A

• Absorption and transport
◦ Molecules are moved out of digestive tract and into
circulation for distribution throughout body

41
Q

what is the movement of Carbohydrates through the digestive system?

A

Mouth: salivary amylase= polysaccharides

Stomach: same

Duodenum: Pancreatic amylase= Disaccharides

Epithelium of small intestine: Disaccharidses= monosaccharides

42
Q

what is the movement of Lipids through the digestive system?

A

Mouth: Lingual lipase

Stomach: Gastric lipase

Duodenum: Bile salts+ Pancreatic lipase

Epithelium of small intestine: fatty acids, monoglycerides

43
Q

what is the movement of Proteins through the digestive system?

A

Mouth: nothing

Stomach: Pepsin= polypeptides

Duodenum: Trypsin, chymotrypsin, carboxypeptidase= peptides

Epithelium of small intestine: peptidases=amino acids, dipeptides, tripeptides

44
Q

Water and ions- water

A

• Water: can move in
either direction across wall of small intestine depending
on osmotic gradients

45
Q

Water and ions-ions

A

• Ions: sodium, potassium, calcium, magnesium, phosphate are actively transported

46
Q

movement of water in the digestive system?

A

mouth: Ingestion (2 L), salivation gland secretions (1 L)
stomach: gastric secretions (2 L)

Duodenum: Bile (0.7 L), Pancreatic secretions (1.2 L)

Epithelium of small intestine: small intestine secretions (2 L) 92% absorbed in the small intestine, 6%-7% absorbed in the large intestine

(water in feces=ingested+ secreted- absorbed)

Anatomy and physiology-Degree (23 decks)

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