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BIO 110 - Anatomy & Physiology > LO 17 > Flashcards

LO 17 Flashcards

1
Q

Describe the overall structure of the digestive system

A
  1. Irregular tube
  2. Open at both ends
  3. Alimentary canal or gastrointestinal (GI) tract
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2
Q

What are the functions of the digestive system?

A
  1. Digestion
  2. Absorption
  3. Metabolism
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3
Q

Describe the wall of the digestive tract

A
  1. Four layers of tissue
  2. Structure varies among organs
  3. From inside to outside, they are: Mucosa, Submucosa, Muscularis, Serosa
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4
Q

Describe the mucosa layer of the digestive tract

A
  1. Produces mucus to coat lining of ‘tube’.
  2. Functions include: Secretion of mucus, digestive enzymes and hormones; Absorbing the end products of digestion; Protection against pathogens
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5
Q

Describe the submucosa layer of the digestive tract

A
  1. Connective tissue layer
  2. Contains blood vessels, lymphatic vessels and nerves
  3. Contains lots of elastic fibres, allowing the tube to stretch and recoil (especially the stomach)
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6
Q

Describe the muscularis layer of the digestive tract

A
  1. Mixes & churns food
  2. Peristalsis
  3. Consists of 2 or 3 layers (depending on location in GI tract): Inner circular (lots at sphincters); Outer longitudinal; Oblique
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7
Q

Describe the serosa layer of the digestive tract

A
  1. Protective outermost layer
  2. Composed of visceral and parietal peritoneum in abdominal cavity
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8
Q

Describe the mouth in terms of the digestive system

A
  1. Where process of digestion begins!
  2. Hollow ‘chamber’
  3. aka ‘oral cavity’
  4. Lined with mucosa
  5. ‘parts’: Roof, Floor, Walls
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9
Q

Describe the roof of the mouth

A
  1. Hard palate (maxillary & palatine bones)
  2. Soft palate (arch-shaped muscle; separates mouth from pharynx)
  3. Uvula – projection of soft palate
  4. Uvula & soft palate prevent food & liquid from entering nasal cavities
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10
Q

Describe the floor of the mouth

A
  1. Tongue and its muscles
  2. Tongue anchored to floor of mouth by the frenulum
  3. Consist of a tip, a body and a root
  4. Small nipple-like projections on tongue, called papillae - Taste buds found in many papillae
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11
Q

What is ankyloglossia?

A
  1. “Tongue-tied”
  2. Frenulum is unusually short and thick
  3. Can be mild (bands) to complete (entire tongue is attached to the floor of the mouth)
  4. Affects feeding/eating, swallowing, oral hygiene/structure, speech
  5. May recede on its own; surgery is an option
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12
Q

Describe the walls of the mouth

A
  1. Lateral walls formed by the cheeks
  2. ‘buccinator muscle’
  3. Anterior wall formed by the lips
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13
Q

Describe gingivitis

A
  1. Inflammation of the gums
  2. Generally limited to superficial gum tissue
  3. Can lead to periodontitis
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14
Q

Describe periodontitis

A
  1. Inflammation of periodontal membrane & supporting tissues (including bone around teeth)
  2. Can lead to loose teeth/loss of teeth
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15
Q

Describe dental carries

A
  1. Disease of enamel, dentin and cementum
  2. Caused by food debris, bacteria & plaque
  3. Leads to the formation of a cavity
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16
Q

Describe the salivary glands

A
  1. Secrete saliva (salivary amylase + mucus)
  2. Parotid glands (largest)
  3. Submandibular glands (‘below mandible’)
  4. Sublingual glands (‘below tongue)
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17
Q

Describe the pharynx

A
  1. Tube-like structure made of muscle and lined with mucous membrane
  2. Dual function: digestion & respiration
  3. Air must pass through the pharynx on its way to the lungs
  4. Food must pass through the pharynx on its way to the stomach
  5. Three divisions: nasopharynx, oropharynx, laryngopharynx
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18
Q

Describe the esophagus

A
  1. Muscular, mucus-lined tube (25cm long)
  2. Connects the pharynx with the stomach
  3. Peristaltic action conducts food to the stomach
  4. Peristalsis- muscle contraction that squeezes food along the digestive tract
  5. Mucous secretion facilitates passage of food
  6. Collapses
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19
Q

Describe the stomach

A
  1. In upper abdominal cavity (just under diaphragm)
  2. Temporary ‘storage’ sac for chewed food
  3. Where chemical digestion of protein begins
  4. Contains HCl (hydrochloric acid) & digestive juices
  5. About the size of a large sausage when empty - expands after large meal
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20
Q

What is the cardiac sphincter (lower esophageal sphincter)?

A
  1. Ring of muscle at end of esophagus
  2. Prevents stomach contents from refluxing back into esophagus
  3. The one at the bottom of the stomach is the pyloric sphincter
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21
Q

What is a hiatal hernia?

A
  1. Due to weakening of ‘hiatus’ (opening in diaphragm for espophagus)
  2. End of esophagus may bulge
  3. Part/all of stomach can bulge upwards
  4. Can lead to GERD
22
Q

What are the 3 sections of the stomach?

A
  1. Fundus – enlarged portion at top
  2. Body – central part
  3. Pylorus—lower part of stomach - pyloric sphincter muscle closes opening of pylorus into duodenum
23
Q

What are the 3 layers of smooth muscle in the stomach?

A
  1. Oblique – innermost (unique)
  2. Circular – middle
  3. Longitudinal – outer

*These make up the muscularis layer

24
Q

Describe the lining of the stomach

A
  1. mucous membrane
  2. microscopic glands secrete gastric juice & HCl into stomach
  3. Mucous membrane lies in folds (rugae) when stomach is empty
  4. Note: food stays in the stomach anywhere from 30 minutes to 2 hours
25
Q

Describe the pyloric sphincter

A

A ring of muscle tissue at the ‘bottom’ of the stomach that food passes through before entering the small intestine

26
Q

Describe the small intestine

A
  1. Main digestive organ
  2. From pyloric sphincter to the ileocecal valve
  3. 7 m (20 feet) long; 2 cm in diameter
  4. 3 divisions: Duodenum, Jejunum, Ileum
  5. Smooth muscle fibers in wall create peristalsis
  6. Lined with mucus membrane that is highly adapted for secretion
27
Q

Describe the lining of the small intestine

A
  1. Adapted for secretion & nutrient absorption
  2. Microscopic ‘intestinal glands’ secrete digestive juices
  3. Arranged into multiple circular folds called plicae
  4. Plicae covered with villi
  5. Villi contain blood capillaries and lymph lacteals for nutrient absorption
  6. Villi covered by microvilli (‘brush border)
28
Q

Describe the liver

A
  1. Largest gland in body
  2. Fills upper right section of abdominal cavity and extends into left side
  3. Secretes bile (cholesterol + bile salts) to emulsify fat
  4. Bile that is eliminated in feces also carries cholesterol from the body
29
Q

Describe the gallbladder

A
  1. Undersurface of liver
  2. Concentrates & stores bile
30
Q

What are the 3 liver/gallbladder ducts?

A
  1. Hepatic ducts - Drain bile from liver
  2. Cystic duct – Bile enters and leaves GB
  3. Common bile duct - Drains bile from hepatic or cystic ducts into duodenum. Blockage (e.g. stone) results in jaundice
31
Q

Describe how the liver/gallbladder release bile

A
  1. Initiated by the presence of fat in chyme
  2. Detection of fat in chyme stimulates release of the hormone cholecystokinin (CCK) from duodenum’s intestinal mucosa
  3. CCK stimulates the contraction of GB, which stimulates secretion of bile into the duodenum
32
Q

Describe the pancreas

A
  1. Located behind stomach
  2. Inside ‘C’ of duodenum
  3. Main duct empties into duodenum
33
Q

Describe the exocrine action of the pancreas

A
  1. Secretes pancreatic juice into pancreatic ducts
  2. Pancreatic juice is most important digestive juice as it contains enzymes to digest all 3 macronutrients
  3. Also secretes alkaline sodium bicarbonate to ‘buffer’ acidic gastric juice that empties into duodenum
34
Q

Describe the endocrine action of the pancreas

A
  1. Pancreatic islets (islets of Langerhans)
  2. These cells not connected with pancreatic ducts
  3. Secrete hormones, glucagon, and insulin into the blood to regulate blood sugar
35
Q

Describe the large intestine

A
  1. Last part of GI tract - 1.5 m (5 ft) long, 6.3 cm (2.5 inch) diameter
  2. Smooth muscle fibres in wall contract for churning & peristalsis for ultimate evacuation of bowel
  3. Lined with mucus membrane
  4. Absorption of water, salts, vitamins
  5. No villi = less surface area/not well suited for absorption compared to small intestine
  6. Undigested food material enters L.I. after passing through the ileo-cecal valve
  7. Water and salts are reabsorbed from semi-solid chyme as it passes through S.I. and becomes more solid in L.I. = feces
  8. Bacteria in L.I. acts on undigested/unabsorbed food material (e.g. cellulose and other fibres) 🡪 additional nutrients released
  9. Bacteria in L.I. also have other functions including synthesis of vitamin K and some of the B vitamins (e.g. B12)
36
Q

It takes ________ days for fecal matter to pass through L.I.

A

3 to 5

37
Q

What is constipation?

A

prolonged time in L.I. leads to more water being absorbed and feces become more solid, harder

38
Q

What is diarrhea?

A

fecal matter rushes through the L.I. before the water is absorbed

39
Q

What are the divisions of the large intestine?

A
  1. Cecum - pouch-like structure at the ileocecal valve
  2. Colon - Many divisions from
    Ascending-transverse-descending colon to the Sigmoid colon
  3. Anus - Opening to exterior; Inner anal sphincter (involuntary muscle); Outer anal sphincter (voluntary muscle)
40
Q

Describe the appendix

A
  1. “vermiform” = worm shaped
  2. Blind tube off cecum
  3. No ‘important’ digestive functions in humans
  4. Beavers use to digests wood/tree bark
  5. Lymphatic tissue
  6. Appendicitis
41
Q

Describe the peritoneum

A
  1. Serous membrane lining abdominal cavity and covering abdominal organs.
  2. Parietal layer
  3. Visceral layer
  4. Peritoneal space - fluid moistens and reduces friction
42
Q

Describe the mesentery extension of the peritoneum

A
  1. Shaped like a pleated fan
  2. Extension of parietal peritoneum
  3. Attaches most of small intestine to posterior abdominal wall
43
Q

Describe the greater omentum extension of the peritoneum

A
  1. ‘lace apron’
  2. Pouch-like extension of the visceral peritoneum
  3. Hangs down from lower edge of stomach and transverse colon over intestines
44
Q

What are the 2 extensions of the peritoneum?

A
  1. Mesentery
  2. Greater omentum
45
Q

Define digestion

A

Process by which foods are altered so that they can be absorbed and used by cells

46
Q

What is mechanical digestion?

A
  1. Mastication
  2. Deglutition-swallowing
  3. Peristalsis/churning/movement
47
Q

What is chemical digestion?

A
  1. Digestive enzymes
  2. Breaks macronutrients into the smallest compounds
48
Q

Describe digestive enzymes

A
  1. Responsible for chemical digestion
  2. Are not changed or used up during process
  3. ‘ase’ = enzyme
  4. Specific enzymes for specific nutrients
  5. Temperature and pH dependent
  6. Hydrolysis – chemical ‘splitting’ (breakdown) of larger molecules by water
49
Q

Describe the digestion of carbohydrates

A
  1. Carbohydrates = sugar & starches
  2. Begins in the mouth (salivary amylase)
  3. None occurs in stomach
  4. Most occurs in small intestine
  5. Polysaccharides are broken into disaccharides, which are broken into monosaccharides
  6. Pancreatic amylase breaks polysaccharides down to disaccharides
  7. Intestinal juice enzymes break disaccharides down to monosaccharides
50
Q

Describe the digestion of proteins

A
  1. Proteins break down into amino acids
  2. Begins in stomach
  3. Completed in small intestine
  4. HCl converts pepsinogen into pepsin
  5. Pepsin: Gastric juice, partially digests proteins
  6. Trypsin: Pancreatic enzyme, continues digestion of proteins
  7. Peptidases: Intestinal enzymes, complete digestion resulting in amino acids
51
Q

Describe the digestion of fat

A
  1. Fat breaks down into glycerol + fatty acids
  2. Most require emulsification by bile
  3. Bile-contains no enzymes but emulsifies fats
  4. Pancreatic lipase - changes emulsified fats to fatty acids and glycerol in small intestine
52
Q

Describe absorption

A
  1. Movement of digested food molecules (amino acids, glucose, fatty acids, glycerol) from the mucous membrane of the intestine into blood or lymph
  2. Small intestine: foods and most water
  3. Large intestine: Some water and vitamins synthesized in the large intestine

BIO 110 - Anatomy & Physiology (16 decks)

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