Chp 23 PP Flashcards
1
Q
Digestive Processes
A
1) Ingestion
2) Movement of food
3) Digestion
- Mechanical digestion
- Chemical digestion
4) Absorption
5) Defecation
2
Q
Digestive organs divided into 2 main groups
A
1) GI (alimentary) tract
2) Accessory structures
- cheeks, teeth, tongue, salivary glands
- liver, gallbladder, pancreas
3
Q
3 pairs salivary glands
A
- Parotid glands
- Submandibular glands
- Sublingual glands
4
Q
digests carbohydrates
A
salivary amylase
5
Q
Functions of Saliva
A
- Water dissolves food for taste and digestion
- Mucous moistens and lubricates food
- Mucous lubricates oral surfaces for smooth actions in swallowing and speech
- Cl- ions activate amylase
- HCO3- and PO4- ions buffer bacterial acids
- IgA, lysozymes, cyanide, defensins: protect against microorganisms
6
Q
what stimulates salivation
A
Food (mechanically, chemically)
behavioral – memories from cortex
starts digestion
continues after ingestion is complete
irritating foods or nausea
7
Q
Functions of Saliva
A
Water dissolves food for taste and digestion
Mucous moistens and lubricates food
Mucous lubricates oral surfaces for smooth actions in swallowing and speech
Cl- ions activate amylase
HCO3- and PO4- ions buffer bacterial acids
IgA, lysozymes, cyanide, defensins: protect against microorganisms
8
Q
Secretion of Saliva - 1-1.5 L l day is under what control
A
Primarily under nervous control
9
Q
if your parasympathetic nervous system is turned on what happens to the salivary secretions
A
normal salivary secretions
saliva swallowed
most reabsorbed
10
Q
if your sympathetic nervous system is turned on what happens to salivary glands
A
reduced flow (dry mouth)
11
Q
mastication
A
Chewing
12
Q
Food mixed with saliva
Shaped into a
A
bolus
13
Q
salivary amylase breaks down and converts polysaccharides (starches
A
to disaccharides (maltose) and monosaccharides (glucose) [no enzymatic action with cellulose which is also a polymer of glucose]
14
Q
how is bolus moved to the stomach
A
through three phases…
buccal
pharyngeal
Esophageal
facilitated by saliva
15
Q
what parts of the body are used to move bolus from the mouth to stomach
A
mouth
pharynx
esophagus
16
Q
buccal phase is
A
Voluntary
Moves bolus to oropharynx
17
Q
Pharyngeal phase
A
-Involuntary
Receptors in oropharynx stimulate medulla and pons to:
1) Block mouth with tongue
2) Block nasopharynx with soft palate
3) Raise larynx to seal epiglottis, blocking airways
4) Relax upper esophageal sphincter
-Bolus is moved through pharynx into esophagus
18
Q
Esophageal stage
A
- Upper esophageal sphincter closes
- Gastroesopaheal sphincter opens
- Esophagus controls involuntary peristaltic movement
- Epiglottis reopens
- Bolus moves from esophagus to stomach
19
Q
Peristalsis
A
Involuntary, rhythmic contraction of muscularis
Controlled by medullary centers
A movement activity: inner circular layer of smooth muscle contracts behind bolus to push it forward; outer longitudinal muscle contracts to pull esophagus wall up
20
Q
Physiology of Esophagus
A
Upper esophageal sphincter
Peristalsis
Lower esophageal (“cardiac”) sphincter
Sharp transition from nonkeratinized stratified squamous epithelium to simple columnar epithilium
Esophageal epithelium resistant to abrasion but not to acid and proteolytic enzyme attack – acid reflux disease
21
Q
Physiology of digestion - Mechanical digestion
A
- peristaltic movement (mixing waves) back and forth between body and pylorus
- 3 muscle layers: longitudinal, circular, and oblique
- chyme
22
Q
Physiology of digestion - Chemical digestion
A
parietal cells secrete intrinsic factor for B12 absorption
parietal cells secrete HCl by active transport
chief cells secrete pepsinogen (inactive precursor)
23
Q
parietal cells secrete HCl by active transport
A
- kills microbes, denatures proteins
- causes some acid hydrolysis of food molecules
- stimulates secretion of hormones for bile & pancreatic juice flow
24
Q
chief cells secrete pepsinogen (inactive precurso)
A
- activated to pepsin by HCl acid and by other pepsins
- only an effective protease at acid pH
- cleaves proteins into smaller peptides
25
Stomach: Mucosa contains
Gastric gland chief cells
Simple columnar epithelium with goblet cells and gastric pits
Simple columnar epithelium with goblet cells and gastric pits
Goblet & gastric pit mucous cells secrete mucin
Gastric gland G cells (enteroendocrine)
26
Gastric gland chief cells secrete
Secrete pepsinogen (inactive precursor)
Secrete rennin in neonates
Secrete gastric lipase in neonates
27
```
chief cells
Secrete pepsinogen (inactive precursor)
```
activated to pepsin by HCl acid and by other activated pepsin enzymes
only an effective protease at acid pH
cleaves proteins into smaller peptides
28
chief cells Secrete rennin in neonates
curdles milk to increase time for gastric processing
29
chief cells Secrete gastric lipase in neonates
splits short chain triglycerides common in milk
| limited role in digestion since it works best at pH 5-6
30
Simple columnar epithelium with goblet cells and gastric pits
Secretes
2-3 L l day
31
Gastric gland parietal cells
| Secrete
intrinsic factor for B12 absorption
HCl by active transport
- kills microbes, denatures proteins
- causes some acid hydrolysis of food molecules
- stimulates secretion of hormones for bile & pancreatic juice flow
32
Goblet & gastric pit mucous cells secrete
mucin
| 1-3 mm mucus layer in the stomach prevents self-digestion
33
Gastric gland G cells (enteroendocrine)
| Secrete
gastrin, histamine, serotonin, somatostatin
34
Absorption
| of mucosa
Impermeable to diffusion of most molecules into the bloodstream
Absorbs a few lipid soluble compounds:
certain drugs (e,g., aspirin)
alcohol
35
Physiology of the liver - processes vital to life
- Storage – oil-soluble vitamins, iron, other nutrients and minerals
- Phagocytosis
- Removal of dietary toxins, hormones, drugs
- --detoxify or store or secrete compounds into bile
- --metabolize thyroid, steroid hormones
- Synthesis of bile salts
- Excretion of bile - bilirubin
- Activation of Vitamin D (?)
36
Pathologies of the liver –
hepatitis (viral, toxic), cirrhosis, cancer
37
Gall Bladder shape
Pear-shaped sac, 7-10 cm long
38
Gall Bladder physiology
- stores and concentrates bile between meals
- CCK stimulates bile release for fatty meals
- when the small intestine is empty, the hepatopancreatic sphincter closes, forcing bile into the gallbladder for storage
39
cirrhosis
harden liver
40
Summary: Digestive Hormones
```
enteroendocrines
Gastrin
Gastric Inhibitory Peptide
Secretin
Cholecystokinin
```
41
Small Intestine: Segmentation
primary action of small intestine when food is present
a form of mechanical digestion
a mixing activity
alternate contraction, relaxation of antagonistic smooth (circular and longitudinal) muscle segments in the intestine
controlled by the autonomic nervous system
42
Small Intestine: Peristalsis
as absorption continues, distension decreases and true peristalsis starts
a movement which propels chyme onward
these weak movements which occur only after most nutrients have been absorbed
43
only fat soluble vitamins
ADEK
44
vitamins that can be toxic to the liver
ADEK
45
Stomach Regulated by combination of
neuronal and hormonal factors
46
3 phases of stomach
Cephalic
Gastric
Intestinal
47
Cephalic phase
stimuli
effect
```
Stimuli
sight
smell
taste
thoughts/memories
```
Effect
Parasympathetic impulses increase gastric secretion
48
Gastric phase neural mechanism
negative feedback
49
in the gastric phase distension activates
stretch receptors causing myenteric and vagovagal reflexes to release Ach
Ach stimulates gastric juice secretion
50
In the gastric phase chemoreceptors respond to
partially digested proteins, caffeine and rising pH
| Stimulate gastrin secretion from G cells
51
```
Gastric phase (cont.)
Gastrin
```
```
Inhibited at pH < 2
Gastrin transported in the blood to the gastric glands
Greatly stimulates HCl secretion
Stimulates histamine secretion
Slightly stimulates pepsinogen secretion
Contracts lower esophageal sphincter
Increases gastric motility
Relaxes pyloric sphincter
```
52
Control of HCl secreting parietal cells happens in what phase
Gastric phase
53
gastric phase is stimulated by three signal chemicals
gastrin
acetylcholine
histamine
54
All three needed for strong H+ secretion
gastrin
acetylcholine
histamine
55
blockage of the histamine H2 receptor decreases
HCl secretion
56
Intestinal phase has
excitatory and inhibitory components:
57
Intestinal phase.... Excitatory
Very short phase
Initiated by chyme entry into duodenum
Stretch receptors stimulate release of intestinal (enteric) gastrin
Chemoreceptors detect fatty acids, & glucose in the duodenum
Stimulate enteric gastrin release
58
Intestinal phase...
| Inhibitory
Enterogastric reflex:
| Enterogastrone secretion
59
Enterogastric reflex
stretch receptors, chemoreceptors trigger 3 reflexes that
1) Inhibit vagoval reflex
2) Inhibit myenteric reflex
3) Activate sympathetic nervous system to close pyloric sphincter
- Inhibit gastric secretion
60
Enterogastrone secretion
Enteroendocrine cells in the small intestine release:
- Cholecystokinin (CCK)
- Gastric inhibitory peptide (GIP)
- Secretin
- Vasoactive intestinal peptide (VIP)
Hormones inhibit gastric secretion
61
Food normally passes through stomach in
4 hours
62
regulate gastric emptying
Hormonal/neuronal reflexes
63
Large meals and large amounts of liquid increase stomach
stomach distension increasing rate of emptying
64
Stomach emptying inhibited by the
enterogastric reflex, enterogastrones, and fat in the duodenum
65
Pancreatic juice
Mostly water some salts, bicarbonate, enzymes
alkaline, pH 7.1-8.2
buffers acidic gastric juice, stops pepsin activity, creates proper alkaline pH for enzymes acting in the intestine
66
pancreatic juice enzymes include
pancreatic amylase
trypsinogen,
chymotrypsinogen,
procarboxypeptidase (inactive zymogens)
pancreatic lipase
ribonuclease and deoxyribonuclease
67
Regulation of Pancreatic Secretion is done by
Neural control from parasympathetic division of ANS via vagus nerve
Autoregulation by sensing the presence of fatty acids and amino acids in the acidic chyme
Hormonal control by the secretion of enteroendocrines from duodenum
Secretin – stimulates secretion of water, HCO3-
CCK – stimulates secretion of enzymes
68
Liver: Blood Supply- two sources
Hepatic artery - oxygenated blood from aorta
Hepatic portal vein -deoxygenated blood:
- absorbed nutrients and toxins from the stomach and intestines
- hormones from the pancreas
- breakdown products of RBCs from the spleen
Blood mixes in the sinusoids
69
(liver cells) modify and exchange molecules with the blood
Hepatocytes
70
livers central veins return blood to
the systemic circulation via the hepatic vein and inferior vena cava
71
Liver bile secretion Bile from the hepatocytes enters
bile capillaries (canaliculi)
Canaliculi empty into small bile ducts
Hepatic ducts join the cystic duct from the gallbladder to form the common bile duct
Gallbladder stores bile
Common bile duct meets pancreatic duct at the hepatopancreatic ampulla (of Vater)
72
Bile
800-1000 ml/day
Yellow, brownish, or olive-green liquid
pH 7.6-8.6, mostly water, bile salts, bile acids, cholesterol, lecithin (phospholipid), bile pigments, ions
Part digestive secretion, part excretory product
- bile salts help in emulsification of ingested fats
- bilirubin and other bile pigments are wastes from lipid catabolism
73
Regulation of bile production/secretion
| nervous control from
parasympathetic division of ANS via vagus nerve
74
Regulation of bile production/secretion
| autoregulation by sensing the
resence of fatty acids and amino acids in the acidic chyme
75
Regulation of bile production/secretion
| hormonal control by
the secretion of the enteroendocrines, CCK and secretin, from the duodenum
76
Liver Lipid metabolism
stores, metabolizes some triglycerides
synthesizes new cholesterol
degrades excess cholesterol for bile salt production
77
Liver Carbohydrate metabolism
regulates blood glucose levels
glycogenesis (insulin)
glycogenolysis (glucagon)
gluconeogenesis (glucagon)
78
Liver protein metabolism
deaminates AA’s by removing amino groups (-NH2) from AA’s
deaminated AA's used for ATP production or changed to carbohydrates or fats as needed
detoxifies ammonia (NH3) by synthesizing urea (1 CO2 + 2 NH3 = urea)
can convert AA's from one to another (transamination)
synthesizes and secretes most plasma proteins
79
Liver metabolize three things
carbohydrate
lipid
protein
80
Physiology of the liver - processes vital to life
| stores
oil-soluble vitamins, iron, other nutrients and minerals
81
Liver removes
dietary toxins, hormones, drugs
detoxify or store or secrete compounds into bile
metabolize thyroid, steroid hormones
82
Liver synthesis
bile salts
83
Liver uses what to break down things
phagocytes
84
Liver excretes
bile - bilirubin
85
Pathologies of the liver
hepatitis (viral, toxic), cirrhosis, cancer
86
Pear-shaped sac, 7-10 cm long
gall bladder
87
gall bladder stores concentrates
bile between meals
88
what stimulates bile release for fatty meals
CCk
89
when the small intestine is empty, the hepatopancreatic sphincter
closes, forcing bile into the gallbladder for storage
90
pathology for the gall bladder is
gall stones
91
what are your digestive hormones aka enteroendocrines
Gastrin
Gastric Inhibitory Peptide
Secretin
Cholecystokinin
92
a form of mechanical digestion in the small intestine
Segmentation
93
primary action of small intestine when food is present
segmentation
94
a mixing activity in the small intestine
segmentation
95
alternate contraction, relaxation of antagonistic smooth (circular and longitudinal) muscle segments in the small intestine
segmentation
96
what system is segmentation controlled by
autonomic nervous system
97
as absorption continues, distension does what and what starts
distension decreases and true peristalsis starts
98
a movement that propels chyme onward
peristalsis
99
these weak movements which occur in the small intestine only after most nutrients have been absorbed
peristalsis
100
Primary active transport electrolyte in the small intestine
Na+
101
facilitated diffusion electrolyte in the small intestine
K+
102
Active Transport electrolyte in the small intestine
Fe
103
which electrolyte in the small intestine is Active transport, vitamin D is a cofactor?
Ca2+
104
Fat-soluble vitamins in the small intestine
ADEK
105
water soluble vitamins in the small intestine
BC
106
What nutrients does the small intestine absorb
Lipids are emulsified by bile salts, forming micelles
107
Small intestine absorbs how many L /day
8.3
108
Total volume of water absorption added to the small intestine/day
9.3
~2.3 L from ingestion
~7.0 L from secretions
109
The rest of the water that isn't absorbed in the small intestine is reabsorbed as
The rest of the water (~1.0L/day) passes to large intestine where most is reabsorbed (~0.9 L/day)
110
Completion of absorption, especially final absorption of H2O
Large Intestine
111
Normal flora manufacture certain vitamins (B complex, K)
| Formation and expulsion of feces
Large Intestine
112
What 4 areas is the large intestine divided into
cecum
colon
rectum
anal canal
113
Chyme passage regulated by?
ileocecal sphincter
114
when the cecum is full, the sphincter is?
contracted
115
Colon movements start when
chyme passes sphincter
116
what does the large intestine digest and through what mechanism
digestion of chyme by bacteria
117
following a meal what occurs in the large intestine
gastroileal reflex: ileal motility increases, sphincter relaxes, chyme moves to the cecum
when the cecum is full, the sphincter contracts
