Digestive System Flashcards
(98 cards)
1
Q
What are the 4 main roles of stomach?
A
- Stores food (2-6 hours)
- Regulates the release of food in the small intestine
- Liquefying food
- Starts chemical digestion of proteins
2
Q
What is called food that enters the duodenum from the stomach?
A
Chyme
3
Q
Mucus cells secrete mucus for what?
A
To protect the cells of the stomach. (New stomach lining every 3 days)
4
Q
Parietal cells secrete what?
A
HCl
5
Q
Chief cells secrete what?
A
Pepsinogen
6
Q
How does pepsinogen become active?
A
It becomes active as Pepsin in the presence of HCl
7
Q
What is called the mixture of Pepsin+HCl?
A
Gastric juice
8
Q
Weak circular muscle surround what and prevent what?
A
It surrounds the cardia, and help prevent reflux of ingesta (stomach content)
9
Q
What happens when the stomach fills with food?
A
It closes the end of the esophagus
10
Q
The closure of the esophagus when the stomach fills with food is very strong in which animals?
A
In rabbits and horses, so reflux and vomiting are nearly impossible
11
Q
At the junction of the esophagus and stomach, what happens to the type of cells?
A
The stratified squamous epithelium of the esophagus changes abruptly to the simple columnar epithelium of the stomach
12
Q
What is the difference between a monogastric and ruminants?
A
Monogastric have a single chamber, while ruminants have part of multi-chambered structure
13
Q
Monogastric is made of how many areas?
A
5:
1. Cardia
2. Fundus
3. Body
4. Pyloric antrum
5. Pylorus
14
Q
What happens in the fundus?
A
Muscles relax (=expand) when swallowing
15
Q
What happen to the body
A
Muscles relax (=expand) when swallowing
16
Q
What happens to the pyloric antrum?
A
Muscles contract (=grind) when swallowing
17
Q
What is the function of the pylorus?
A
It regulates one-way movement towards the duodenum
18
Q
What is the duodenum?
A
First part of the small intestine that receives partially digested food from the stomach, absorbs nutrients and discharges digested food into the jejunum.
19
Q
Liquids will reach duodenum slower or faster than solids?
A
Liquids are faster than solids
20
Q
What happens when there is an increase of HCl in duodenum?
A
Secretin is release from it to relax fundus and inhibit peristalsis of body/antrum
21
Q
What happens when there is an increase of lipids/proteins in duodenum?
A
Cholecystokinin (CCK) has the same effects as secretin + raise pH + promotes secretion of alkaline bile into duodenum
22
Q
What is the function of goblet cells of gastric glands?
A
Mucin + bicarbonate ion to counter HCl
23
Q
What are the 3 main roles of the small intestine?
A
- Chemical absorption
- Absorption
- 3 specialized regions: Duodenum, jejunum (longest portion) and ileum (separated from the colon by ileocecal sphincter; muscle that moves content into the colon
24
Q
Why does absorption works great in the small intestine?
A
Because of its structure: Circular folds + Villi (x10) + Microvilli (x20) = surface area of 300 to 600 m^2
25
Most of the digestion in the small intestine is performed by what?
Pancreatic enzymes
26
Bile is made of what?
- Water + ions + cholesterol
27
Where is bile produced and stored?
Bile is produced by the liver, and stored in the gallbladder
28
What is the function of bile?
Acts to separate fat into small droplets (problem: fat is insoluble in water, and lipase is soluble in water)
29
What are brush border enzymes?
They perform the final digestion of food into the simple components that can be absorbed by intestinal cells. Those enzymes are not secreted. Instead, they remain bound to the plasma membrane of the enterocytes.
30
Where is the majority of the nutrients absorbed?
Into the bloodstream
31
What occurs during carbohydrate digestion?
Amylase (saliva, pancreas into duodenum) converts starch into disaccharides, which are then converted into monosaccharides by enzymes found in the microvilli
32
What occurs during protein digestion?
- Pepsin
- Pancreas makes trypsin, chymotrypsin, elastin, aminopeptidase and carboxypeptidase
- Villi peptidases complete digestion of proteins into single amino acids
33
What happens during emulsification (fat digestion) ?
Breaking up of fat globules into much smaller emulsion droplets
34
Are lipids hydrophilic or hydrophobic?
Lipids are hydrophobic, poorly soluble in the aqueous environment of the digestive tract
35
What does pyloric antrum do during fat digestion?
Breaks fat globules into small emulsion droplets
36
Bile acids do what?
They are amphipathic, and they are secreted from the liver into the duodenum to stop droplets from forming back into globules
37
What does pancreas secrete?
Lipase to convert droplets into smaller pieces (micelles)
38
Micelles are absorbed by what?
Villi
39
What are chylomicrons?
Fat digestion products coated with proteins?
40
What happens to them because of the fact that they are too big?
They cannot enter blood capillaries. Instead, they enter the lacteal vessel, which is a lymph vessel, to eventually enter the bloodstream.
41
What is the function of the large intestine?
- Absorb most (90%) of the water remaining (adjusting consistency of waste)
- Stores feces
- Eliminate feces from the body
- Also absorbs sodium an potassium ions
- Bacteria produces vitamin K (we are unable to produced it)
42
What is defecation?
Expelling feces
43
What is the rectum?
- Terminal portion of the large intestine, similar mucus-secreting glands
44
Rectum acts as what?
A reservoir of feces
45
What are sensory receptors for?
Detect stretching, which stimulates defecation
46
What happens as the rectum fills?
The stretch receptors cause relaxation of the internal sphincter, allows more fecal content to move, more receptors are triggered...
47
What happens to the voluntary motor neurons of the external sphincter when defecation occurs?
They are inhibited
48
What is the anus?
Internal (involuntary) and external (voluntary) muscular sphincter
49
What are the functions of the liver?
- Filters materials absorbed by the GI tract before entering systemic circulation
- Storage of further transforms, depending on the body's needs
- Produces bile (stored in the gallbladder; horses don't have one)
- Produces blood protein albumin (maintain fluid balance within blood)
50
What forms and breaks glycogen?
- Glycogenesis forms glycogen
- Glycogenolysis breaks glycogen
51
Which system is concerned with the liver?
Hepatic portal system
52
What are the functions of pancreas?
- Exocrine (amylase, protease, lipase, bicarbonate secreted into the small intestine)
- Endocrine gland (insulin, glucagon secreted int the bloodstream)
53
Energy is measured in what?
Calories (amount needed to raise 1g of water 1degree)
54
How are the substances that the body cannot make called?
Essential (like essential amino acids)
55
What can provide energy?
Lipids, carbohydrates and proteins
56
What is needed but does not provide energy?
Vitamins, minerals, water and fiber
57
What are dietary fibers?
They are the indigestible portion of food derived from plants
58
Alimentary canal includes what?
- Mouth
- Pharynx
- Esophagus
- Stomach
- Small intestine
- Large intestine
- Anus
59
Accessory organs include what?
- Teeth
- Tongue
- Gall bladder
- Glands (salivary glands, liver, pancreas)
60
Most digestive organs reside where?
In the abdominopelvic cavity
61
What is the peritoneum?
Serous membrane of that cavity, secretes fluid to help reduce friction
62
What is the mensentery?
- Double layer of peritoneum
- Provides routes for blood vessels, lymphatic vessels, nerves, to reach the organs
- Hold organs in place
- Store fat
63
Retroperitoneal organs include what?
Parts of the pancreas, duodenum, parts of the large intestine
64
What can mucosa secrete?
- Mucus, which allows food to slide easily (also a form of protection), mostly simple columnar epithelium
- Digestive enzymes, which chemically digests food
- Hormones
- Can be highly folded for better absorption of nutrients
65
What is submucosa?
- Consists of connective (support) tissue, elastic fibers
- Contains blood vessels, lymph vessels and nerves
66
What is muscularis?
- Responsible for movement and mixing food with digestive secretions
- In most sections, it is a double layer (q circular and 1 longitudinal) of smooth muscles (stomach has 3 layers)
67
What is Peristalsis?
Name of the movement that propels the food down the tube
68
How are sphincters formed?
From thickened layer of muscle
69
What is serosa?
Epithelial tissue + Connective tissue, lubricated so that it reduces friction with the other organs of the body (protection)
70
What occurs during splanchnic circulation?
Arteries that branch of the abdominal aorta to serve digestive organs and hepatic portal (receives 25% of blood supply, increases with meal)
71
What does the celiac trunk serve?
It serves spleen, liver, and stomach
72
What does mesenteric arteries serve?
It serves small and large intestines
73
What occurs in the portal vein?
75% of total liver blood flow is through the portal vein, with the remainder coming from the hepatic artery
- supplies the liver with metabolic substrates
- ensures that substances ingested are first processed by the liver before reaching the systemic circulation (possible toxins that may be ingested can be detoxified + liver is the first organ to absorb nutrients just taken in by the intestines)
74
Sight of food, thought of food, presence of food in the mouth is a stimulus that releases what?
It releases saliva from salivary glands
75
What does the stimulus of chewing food do?
Release of gastric juice (enzymes from stomach and HCl) and mucus from cells of stomach lining
76
The presence of acidic chyme in small intestine is a stimulus that releases what?
It releases enzymes from small intestine and pancreas into the small intestine; release of bile from gallbladder into small intestine; increased motility in small intestine
77
What does the mouth (oral and buccal cavity) do?
- Begins mechanical and chemical digestion
- Monitors food quality
- Moistens and manipulates food to permit swallowing
78
What is the palate?
Roof of the mooth
79
What do salivary glands secrete?
(3 pairs) secrete saliva, which contains amylase, an enzyme that digests starch (chain of sugar produced by plants) into shorter chains of sugar
80
What is bolus?
The name given to food that is swallowed
81
What are the functions of the mouth?
- Prehend
- Mechanical digestion
- Chemical digestion (Amylase digests amylose in omnivores, lipase digests lipids in young animals)
82
What is the structure of the mouth?
- Lips, cheeks
- Tongue
- Teeth
- Salivary glands (parotid, mandibular, sublingual)
- Saliva: digestion, lubrication, taste (dissolving chemicals)
- Hard palate
- Soft palate
- Oropharynx
83
Saliva is made of what?
- 99% of water
- Digestive enzymes:
- Salivary amylase
- Lingual lipase (makes only a minor contribution to overall fat digestion)
- Proteins mucin (lubrication), lysozyme, defensins, and IgA
- Metabolic wastes (urea and uric acid)
84
What is the pH of saliva?
pH 6.75-7
85
What is the amount of saliva produced per day?
About 1.5 L
86
Secretion of saliva is activated by what?
By stimuli + parasympathetic nervous system (autonomous)
87
Stress/dehydration will reduce what?
Salivation through sympathetic nervous system (autonomous)
88
What are the electrolytes?
- Na+
- K+
- Cl-
- PO43-
- HCO3-
89
What is the structure of teeth (mastication)?
- Incisors (cut)
- Canines (tear, pierce)
- Premolars and molars (grind, crush)
90
What is the hardest surface in teeth structure?
Enamel (calcium, hydroxyapatite). It cannot regenerate because cells are lost when tooth erupts
91
What is dentin?
Dentin is protein-rich, more flexible than enamel, shock absorber
92
Why are enamel, dentin and cement not bone?
Because they are not vascular
93
The primary dentition consists of how many teeth?
- 2 incisors
- 1 canine
- 2 molars
*On each side of each jaw, for a total of 20 teeth
94
The permanent dentition consists of how many teeth?
- 2 incisors
- 1 canine
- 2 premolars
- 3 molars
*On each side of each jaw, for a total of 32 teeth
95
What is the pharynx (throat)?
- Oropharynx
- Laryngopharynx: Shared passageway by the respiratory and digestive system
96
Swallowing consists of what?
- A voluntary phase, where the esophagus is closed
- An involuntary phase, where the epiglottis closes the opening to the respiratory system, preventing food from entering, and the esophagus is open.
97
What is the esophagus?
Muscular tube that conducts food from the pharynx to the stomach
98
Deglutition involves what?
The mouth, the pharynx, and oesophagus
