Test 3 Flashcards
1
Q
Chemical Digestion
A
Enzymatic breakdown of large molecules into monomers
2
Q
protection
A
- the mucus secretions in the stomach that help protect the mucosa against HCl
- Protection of the body against infection (acids, enzymes, lymphatic tissues destroy infectious particles.
3
Q
what are the parts of digestion
A
Ingestion mechanical digestion chemical digestion absorption defecation protection propulsion
4
Q
catabolism
A
the breaking of large molecules to smaller molecules
5
Q
protein
A
subunits: amino acids
enzyme: Protease
6
Q
carbohydrate
A
subunit: simple sugars
enzyme: amylase
7
Q
lipids
A
subunit: fatty acids
enzyme: lipase
8
Q
peritoneum
A
a serous membrane (double-layered membrane with fluid in between) that lines the abdominal cavity.
9
Q
visceral peritoneum
A
exterior surface of abdominal organs
10
Q
parietal peritoneum
A
lines the body wall.
11
Q
What is the fluid in the peritoneum called
A
Peritoneal fluid
12
Q
mesentery
A
double-fold of peritoneum that is fused together; mesenteries extend from the body wall to the organs.
13
Q
reason for mesentery
A
- To hold and support blood vessels, lymphatic vessels, and nerves that supply the organs of digestion.
- To hold organs in place in the body (prevent intestines from becoming tangled, help resist the force of gravity against the organs)
- Fat storage.
14
Q
types of movement in the digestive tract
A
- Propulsion
- Segmentation
15
Q
propulsion
A
is the term for food moving distally (away from mouth) in the GI tract.
16
Q
two parts of propulsion
A
swallowing and peristalsis
17
Q
peristalsis
A
are alternative waves of contraction and relaxation of muscles
18
Q
segmentation
A
segments of the GI tract contract and relax.
-Food is moved forward and then backwards, this is a kind of mechanical processing to mix and break down food. Non-directional movement (is not propulsive)
19
Q
parts of the alimentary canal
A
- Mucosa (closest to lumen), 2. Submucosa 3. Muscularis Externa 4. Serosa (or adventitia)
20
Q
functions of mucosa
A
Secretes mucus (goblet cells)
May secrete enzymes
Often absorbs monomers
Acts as a barrier that protects the body from infection
21
Q
potential parts of the mucosa
A
Epithelium
- Lamina propria (connective tissue)
- Muscularis mucosae
22
Q
submucosa
A
Made of dense connective tissue
Contains nerves, lymph & blood vessels, glands are often located in this layer.
May contain specialized structures like Peyer’s Patches (Ileum) and Brunner’s glands (duodenum)
23
Q
Peyer’s patches
A
masses of lymphoid tissue that fights infection.
located in the ileum
24
Q
brunner’s glands
A
secrete alkaline (high pH) mucus that helps to neutralize stomach acid located in the duodenum
25
muscularis externa
Muscularis Externa:
Mixes/propels food
Usually 2 layers of smooth muscle: Circular and Longitudinal
Innervated by myenteric plexus nerves
26
Serosa/adventitia
Contains epithelium & connective tissue
The serosa layer is made of visceral peritoneum (reduces friction)
In some parts of the GI tract (esophagus), this outer layer is adventitia, a fibrous layer that attaches the part of the body wall (different then the function of serosa).
27
serosa compared to adventitia
serosa is visceral peritoneum and adventitia is a fibrous outer layer that is used to connect to the alimentary canal to the things around it.
28
nervous system control
Short reflexes:
| Long reflexes:
29
Short reflexes
: controls segmentation and peristalsis
30
Long reflexes
integrates the central nervous system and extrinsic autonomic nervous system, either enhancing or inhibiting digestive activities.
31
local factors
pH, physical or chemical stimulation.
32
hormonal
18+ hormones that control most aspects of GI function.
33
things that control the digestive process
nervous system
local factors
hormonal
34
digestive processes that occur in the oral cavity
Ingestion (this only happens in the mouth!)
Begins mechanical breakdown by chewing
Starts chemical digestion (breakdown of carbohydrates by salivary amylase)
Initiates propulsion by swallowing
35
types of teeth
1. Incisors cut food
2. Canines tear food
3. Premolars crush food
4. Molars grind food
36
make up of saliva
- Water (the main ingredient)
- Electrolytes (like K+, Cl-, Na+)
- Proteins, including enzymes and mucins
- Antibodies and lysozyme (inhibit infection)
37
functions of saliva
1. Cleanses the mouth
2. Dissolves food chemicals so that they can be tasted
3. Moistens food (lubricates food, makes chewing and swallowing easier)
4. Begins chemical digestion with the enzyme amylase.
38
what part of the alimentary canal has SSE
the pharynx and esophagus
39
what is the esophagus
a hollow muscular tube that begins posterior to the pharynx, and joins the stomach at the cardiac sphincter.
40
cardiac sphincter
the sphincter on the superior section of the stomach
41
four layers of the esophagus
Mucosa: Stratified squamous epithelium
Submucosa: contains esophageal glands (secrete mucus, lubricates bolus of food)
Muscularis externa - Circular muscle in superior region prevents air from entering the esophagus and stomach during breathing
Superior 1/3 = skeletal muscle, Middle 1/3 = mix of smooth/skeletal muscle,
Inferior 1/3 = smooth muscle
No serosal layer, adventitia instead
42
buccal phase
voluntary swallowing
43
Pharyngeal-esophageal phase
involuntary start of peristalsis
44
bolus
food before stomach
45
chyme
food after stomach
46
Histology of the stomach:
Mucosa
Lined with simple columnar epithelium
Contains gastric pits: these are lined by specialized cells that produce gastric juices (includes hydrochloric acid, pepsin, gastric lipase, hormones)
Hydrochloric acid (HCl) leads to a stomach pH of 1.5-3.5 (very acidic).
Muscularis Externa
3 layers of muscle (compared to the 2 layers in much of the rest of the GI tract)
oblique, circular, longitudinal
47
reflex Phase
Occurs before the food enters the stomach
Brain triggers stomach to secrete gastric juices, prepares the stomach for digestion
Triggered by:
Sight or thought of food
Stimulation of taste and smell receptors
Inhibited by:
Loss of appetite (can be caused by depression)
48
Gastric Phase
1. Gastric secretion is triggered by food entering the stomach
2. Distension triggers short & long reflex
Peptides create low acidity (high pH), Gastrin is secreted
Gastrin increases HCl production
More protein in a meal= more gastrin and HCl released.
Triggered by:
Stomach distension
Food chemicals (i.e. peptides)
High pH
Inhibited by:
Stomach pH below 2.0 (decreases gastrin production, reduces HCl)
Emotional stress/fear
49
The intestinal phase (as food is leaving stomach)
triggered by:
Chyme fills the duodenum, which stimulates mucosal cells to release intestinal gastrin.
The intestinal phase (or food leaving stomach) is inhibited/slowed by:
Distension of duodenum
Fatty or acidic chyme triggers a reflex that inhibits HCl production in the stomach.
50
Gastric emptying happens in 3 stages:
1) Propulsion- peristaltic waves move bolus toward the pylorus
2) Grinding- vigorous mixing and churning occurs near the pylorus, a small portion of chyme is moved into the pylorus and then duodenum.
3) Retropulsion- the pyloric sphincter is closed, which forces most of the stomach contents backwards into the stomach. This allows the stomach contents to be digested for long enough, and to prevent the duodenum from being overloaded.
51
parts of the small intestine
1) Duodenum:
2) Jejunum:
3) Ileum:
52
1) Duodenum:
Shortest segment
Contains Brunner's glands in the submucosa
Duodenal ampulla, a union of the common bile duct and pancreatic duct
This ampulla carries secretions from the accessory organs: the liver, gallbladder, and pancreas to alimentary canal (specifically into the duodenum)
53
2) Jejunum
middle section
54
3) Ileum:
The longest segment of the small intestine.
Contains Peyer's patches in the submucosa
The last part of small intestine, empties into the large intestine
55
role of the small intestine
The small intestine plays key role in digestion and absorption of nutrients
90% of nutrient absorption occurs in the small intestine
56
liver functions
1) Metabolic regulation: waste product removal, nutrient storage (such as glycogen, a storage form of glucose)
2) Hematological regulation: the liver is the largest blood reservoir in the body, is important in removal of toxins from the blood.
3) Bile production (important for digesting fats).
57
gallbladder
stores and concentrates bile.
58
bile
a thick digestive fluid that helps digestion by emulsifying fats
59
bile salts
are acids derived from cholesterol. Bile salts emulsify fats before broken down by enzymes
60
bile pigments
Bilirubin is a waste product that comes from hemoglobin (old, worn-out red blood cells are filtered by the liver (hematological regulation).
Metabolized in gut to form urobilinogen, a substance that makes feces brown.
61
hepatocytes
(liver cells) are arranged into lobules, which are separated by a septum. In the septa between lobules are numerous portal triads.
-make bile and glycogen and detox blood
62
Portal triads
contain a bile duct, a portal venule, and a portal arteriole
Blood flows from portal venule and portal arteriole through sinusoids to the central vein (responsible for the blood flow out of liver).
63
Hepatic macrophages
cleanse blood as it is filtered through the liver.
64
the pancreas
a mixed endocrine and exocrine gland
Exocrine portion functions in digestion
Exocrine gland composed of two cell types: Acinar and Duct cells
65
acinar cells
produce digestive enzymes: Proteases, Amylase, Lipase
66
Duct cells
a bicarbonate -rich fluid (pH ~ 8)
| This helps to neutralize stomach acid
67
what pH do enzymes work best that are used in small intestine.
pancreatic amylase, lipase, & proteases work best close to a neutral pH
68
pancreatic amylase
continues the digestion of starch that began with salivary amylase. This process was disrupted by amylase being destroyed by the stomach’s low pH.
69
brush border enzymes
complete the breakdown of starch into individual simple sugars that can be absorbed by the blood stream.
70
small intestine mucosa
Contains villi and microvilli
Lined by simple columnar epithelium
contains many goblet cells (mucus secretion)
Intestinal crypts: secrete intestinal juices that contribute to digestion/absorption, secrete lysozyme (fights infection)
71
sub mucosa
the Duodenum contains Brunner's glands, which secrete alkaline (high pH) mucus that helps to neutralize stomach acid in the duodenum
The Ileum contains Peyer's Patches, which are masses of lymphoid tissue that fights infection.
72
1) Plicae circularis (circular folds)
- permanent folds in the mucosa and submucosa
| - help to mix the chyme and slow down the movement of chyme
73
2) Villi
- Finger-like projections of mucosa; increase surface area
- Lacteals: Modified lymphatic capillaries that absorb lipids
- Also contain capillaries which absorb other nutrients into the bloodstream.
74
3) Microvilli (“brush border”)
- Tiny finger-like projections of the endothelial cell membranes (like villi on top of the villi!)
- Contains the “brush border” enzymes needed to activate pancreatic enzymes
75
what controls segmentation
controlled by pacemaker cells
76
absorption in large intestine
water from indigestible food & vitamins from bacterial products
77
which vitamins are absorbed in the large intestine?
K & some B’s
78
propulsion in the large intestine
Haustral (pockets) contractions – every 30 min, local control
Mass movements (peristalsis) – long, slow, powerful contractions that propel the feces distally.
Intestinal reflexes: Triggered by food in stomach, small and large intestine
Mediated by enteric nerves & hormones
79
Anal columns
allow flatulence to occur without defecation
80
defecation proces
Stretching of rectum signals the sigmoid/rectum to contract; anal sphincters relax
Conscious control can override contraction; decide if the anal sphincter should open, or temporarily remain constricted.
81
microbiome facts
-There are nearly 10x as many bacterial cells living on/in us then there are human cells!
-There are ~2 ¼ pounds of bacteria in a person's large intestine
-Gut bacteria supply nutrients (vitamins K & B), defend against infection by harmful bacteria.
-Breakdown indigestible carbohydrates with fermentation, this produces molecules that the gut can absorb.
-Also produces odorous gases (dimethyl sulfide, methane, etc).
~500 mL gas (flatus) is produced each day.
-The gut begins to be colonized at birth, changes throughout our lives.
-Increasing evidence that our gut bacteria composition can contribute to some health issues, such as obesity.
82
peritonitis
the inflammation of the peritoneal membranes; this causes the serous membranes to stick together.
May be caused by a puncture wound, a perforating ulcer (an ulcer that goes through all 4 layers of the stomach), burst appendix, or poor surgical technique.
It is usually caused by infection, and may be life-threatening.
Most commonly cause is a burst appendix, which sprays bacteria-laden feces into the (normally sterile) peritoneum.
83
Heartburn/ acid reflux
occurs when acid moves up into the esophagus past the cardiac sphincter, causing a painful burning sensation behind the heart.
84
Gastric Ulcer
are a breach in the mucosal barrier
(a penetrating ulcer can lead to peritonitis!)
90% of all ulcers are caused by bacteria called H. pylori.
Other causes? Usually due to long-term NSAID use.
85
Gallstones
-hardened deposits of bile
-Usually will not have symptoms unless a gallstone becomes lodged in one of the ducts (cystic, common bile, pancreatic ducts).
Gallstones can get stuck in a duct and cause blockage, this leads to pain from the stone’s lodging and backup/blockage of secretions.
Symptoms: sudden intense pain, nausea, high fever with chills.
The exact cause of gallstones is unknown; seems to be related to too much cholesterol or bilirubin in the bile.
If symptomatic, gallstones can be treated with ultrasound vibrations, drugs to dissolve the stones, laser vaporization, or surgical gallbladder removal.
86
Nucleic acids
Pancreatic nucleases turn DNA and RNA into nucleotide monomers
Nucleotides (monomers of DNA and RNA) are broken by brush border enzymes
Products actively transported across epithelium
87
Vitamins
Fat soluble absorbed into body in micelles
Water soluble diffuse in small intestine
Vitamin B12: too large & charged – binds to a factor produced by cells in gastric pits & then complex is endocytosed
88
electrolytes
Come from food & secretions
Most diffuse through membranes, some are pumped across membranes
Some are hormonally regulated – Na, Ca & Fe
89
Water
Osmosis (diffusion of water from high to low concentration)
>90% of water is absorbed at the small intestines
~6% of water is reabsorbed at the large intestine.
90
what is a calorie
1 calorie can heat one kilogram of water one degree C
91
Temperature too high
Vasodilation
| Sweat glands stimulated
92
body temperature too low
The sympathetic nervous system decreases blood flow to dermis
Blood is shunted to deep veins for countercurrent exchange
Shivering (muscle movement generates heat).
