GI and Respiratory Physl Flashcards
1
Q
Functions of the GI tract?
A
Digestion
Absorption
Excretion
Host defense
2
Q
Digestion
A
Physical breaking down of food consumed into absorbable nutrients for the body to use, through the use of GIT motility, pH changes, enzymes and detergents.
3
Q
Absorbtion
A
Taking in nutrients consumed from the intestines to the blood of lymphatic system, for body to use.
4
Q
Excretion
A
Removal of waste products that could not be absorbed by the body.
5
Q
Host defense
A
GIT forms a barrier with outside environment and contains a highly developed immune system; GIT can inactivate harmful bacteria
6
Q
Components of the GI tract
A
Mouth, pharynx, esophagus, stomach, small intestine (duodenum, jejenum, illeum), large intestine
7
Q
Accessory organs
A
Pancrease, liver, gallbladder
8
Q
GI tube structure
A
Top third of esophagus: skeletal muscle
Rest of GI tract: smooth muscle
9
Q
Villi
A
Found in the intestinal tube
Project into the lumen
Below surface there is a crypt or invagination
10
Q
Layers of the GIT
A
Mucosa
Submucosa
Muscaleris externa
Serosal layer
11
Q
3 layers of the mucosa
A
Epithelium
Lamina propria
Muscalaris mucosa
12
Q
Epithelium & its function
A
Layer of cells that lines all body cavities and surfaces
Function:
-selective uptake of nutrients, electrolytes, water
-prevent harmful substances from coming through
13
Q
Apical surface
A
Faces the inside of the tube/lumen
14
Q
Basolateral surface
A
Closest to the blood surface, away from the lumen
15
Q
How is SA increased?
A
Presence of villi, microvilli, and crypts
Folds
16
Q
Where do epithelial cells come from?
A
From stem cells within the crypt that differentiate into a variety of cells
17
Q
2 pathways that chemicals use to cross the epitherlial layer?
A
Paracellular pathway
Transcellular pathway
18
Q
Paracellular pathway
A
Chemicals move between cells across the tight junctions; only water and small ions can diffuse across
19
Q
Transcellular pathway
A
Cross the cell by using transport proteins
20
Q
Lamina propria
A
Consists of connective tissue, blood vessels, nerve fibers, lymphatic vessels, inflammatory cells
21
Q
Muscularis mucosa
A
Thin layer of smooth muscle
May be involved in moving villi
22
Q
Submucosa
A
Under mucosa layer
Contains blood vessels, lymphatic vessels, submucosal nerve plexus, connective tissue
23
Q
Submucosal nerve plexus
A
Relays info to and from the mucosa
Influences secretion
24
Q
Muscularis externa
A
Contains circular muscle, myenteric nerve plexus, longitudinal muscle
25
Circular muscle
Fibers are in a circular pattern to contract and relax in order to open/close the tube
26
Myenteric nerve plexus
Regulates the smooth muscle function of the GIT
27
Longitudinal muscle
Lengthens/shortens to control length of tube
28
Serosa
Connective tissue layer and forms connections between the intestine wall and abdominal wall
29
Portal circulation and its purpose?
Carries blood from intestinal tract to the liver
| Important in removal of harmful substances, via the liver
30
Hepatic artery
Carries oxygenated blood from the heart to the GI organs and liver
31
Hepatic portal vein
Carries less oxygenated blood to the liver that has already been perfused by the GI tract organs
32
In series circulation vs in parallel
For in parallel, blood goes directly to the target organ, while in series, blood perfuses the organ/tissue after already perfusing a separate one prior to.
Liver predominantly has in series circulation, leading to blood high in nutrients but lower in oxygen.
33
What 2 factors regulate secretion and motility in the GI tract?
Volume and composition of what's inside
34
Reflexes regulating secretion and motility in the GI tract are initiated by? (3)
1. Distension of GI wall by volume of luminal contents
2. Osmolarity of contents pH
3. Concentration of specific contents like monosaccharides, fatty acids, peptides, amino acids
35
Reflexes are propogated by which receptors?
Mechanoreceptors- activated by pressure, stretch
Osmoreceptors- activated by change in osmolarity
Chemoreceptors- activated by chemicals
36
Enteric/intrinsic regulation
Occurs completely within the GI
Involves the myenteric and submucosal plexi.
Critical for involuntary functions like digestion
Can function independently of the CNS
37
Extrinsic regulation
Occurs outside the GI walls, in the ANS
38
Sympathetic GI responses
- small volume of thick saliva
| - peristalsis and secretion inhibited
39
Parasympathetic GI responses
- large volume of watery saliva
- increases peristalsis and secretion
- stimulates bile release
40
Long reflex
Extrinsic pathway. CNS is stimulated by smell of food for example and eventually GI tract is stimulated to break down food.
41
Short reflex
Intrinsic pathway. Same response is geenrated in Gi tract without any input from CNS. Simply due to food consumption and receptors detecting it, causing a response.
42
4 types of chemical messenger regulation?
Endocrine
Neurocrine
Paracrine
Autocrine
43
Endocrine regulation
Hormone-secreting gland secretes a hormone into the blood, and then travels via blood to its target cells
44
Neurocrine regulation
Nerve cell produces an electrical signal which causes release of a NT that travels across a synapse to a post synaptic target cell (usually an effector, or nerve cell)
45
Paracrine regulation
Cell releases a paracrine substance which diffuses through ISF and acts on target cells nearby the release site.
46
Autocrine regulation
Cell releases autocrine substance which acts in the cell that released it
47
CCK is stimulated by?
Presence of fatty acids and amino acids
48
What doe CCK do?
Stimulated pancreas to increase digestive enzyme secretion, and stimulates gallbladder to contract in order to release bile acids for fat breakdown
49
Intestinal motility? How is it stimulated?
Causes contents to move along GI tract. Stimulated by contraction and relaxation of the 2 muscle layers
50
Peristalsis and how it works?
Main driving force for food moving down the GI tract.
| Circular muscle contracts on oral side of bolus while longitudinal muscle relaxes, and vice versa.
51
Segmentation and its functions?
Contraction and relaxation of intestinal segments (little movement towards large intestine)
Allows mixing of contents
Causes delayed transit time, allowing more time to absorb nutrients
52
Pacemaker cells
Located in the smooth muscle of GIT and are constantly under spontaneous depolarization-repolarization cycles
53
Slow waves
Give the GIT the basic electrical rhythm
With an excitatory input, slow waves are depolarized over threshold and an action potential occurs leading to muscle contraction.
54
Frequency of contraction is dictated by?
Basic electrical rhythm
55
Force of contraction is dictated by?
Hormonal and neuronal input
56
3 phases of GI control?
Cephalic
Gastric
Intestinal
57
Cephalic phase and how its initiated? Reflexes?
Initiated by stimulation of receptors in the head through sight, smell, taste, chewing of food, emotional state.
Reflexes regulated by parasympathetic fibers that activate neurons in the neuronal plexuses.
58
Gastric phase and how its initiated? Reflexes?
Receptors in stomach are stimulated by stretching, distension, acidity, peptide, amino acids.
Short (gastrin) and long (ACH) neural reflexes.
59
Intestinal phase and how its initiated? Reflexes?
Receptors in intestine are stimulated by osmolarity, stretch, distention, digestive products.
Short and long neural reflexes and by CCK, secretin, GIP hormones.
60
Hypothalamus role
Maintains homeostasis
Command centre for neural and endocrine control coordination
Control of behaviour
61
Feeding centre? Lesion causes what?
Located in the lateral region of hypothalamus
Activation of this centre increases hunger
Lesion causes weight loss
62
Satiety centre? Lesion causes what?
Located in the ventromedial region of hypothalamus
Activation makes you feel full
Lesion causes weight gain by overeating
63
Orexigenic factors and examples
```
Increase appetite
Neuropeptide Y (secreted by hypothalamus)
Ghrelin (by stomach endocrine cells)
```
64
Anorexigenic factors and examples
```
Decrease appetite
Leptin (by adipose tissue)
Insulin (by pancreas)
Peptide YY (by intestine)
Melanocortin (by hypothalamus)
```
65
How does ghrelin work?
Secreted by endocrine cells of stomach when body is in fasting state. Ghrelin is released in blood and travels to hypothalamus to stimulate release of neuropeptide Y to try to increase food intake.
66
Lack of leptin results in?
No appetite regulation, obesity
67
What 3 factors stimulate the thirst centre?
1. Increased plasma osmolarity
2. Decreased plasma volume
3. Dry mouth or throat
4. Prevention of over hydration
68
Increased plasma osmolarity
Stimulates osmoreceptors and the release of vasopressin or ADH to conserve water at kidney
69
Decreased plasma volume
Decrease in blood volume and pressure stimulates baroreceptors and will alter sympathetic and parasympathetic outflow to increase arterial pressure to normal levels
70
Intrarenal baroreceptors
When blood pressure in kidneys decreases, baroreceptors are stimulated and acitvation of the renin-angiotensin system occurs. This system produces angiotensin II affects hypothalamus and has been shown to to increase thirst in animals.
71
3 main pairs of salivary glands?
Parotid
Submandibular
Sublingual
72
Composition of saliva
Hypotonic and slightly alkaline.
Made of water, electrolytes (potassium and bicarbonate), digestive enzymes (lipase, amylase), glycoproteins (mucin), antimicrobial factors (lysozyme, lactoferrin)
73
Lysozyme
Breaks down bacterial cell walls
74
Lactoferrin
Prevents multiplication of bacteria by chelating iron
75
Functions of saliva (6)
Moistens/lubricates food to make it easier to swallow
Initiates digestion with digestive enzymes
Allows small bit of food to dissolve through taste buds
Prevents microbial colonization due to antibacterial factors
Aids in speech
Buffer- neutralizes acidic food or acid reflux
76
3 cell types that make up salivary glands?
Acinar cells
Ductal cells
Myopithelial cells
77
Acinar cells
Secrete initial saliva
78
Ductal cells
Create the alkaline hypotonic nature of saliva
79
Myoepithelial cells
Contain characteristics of both epithelial cells and smooth muscle cells
80
Saliva movement
Moves from the acinus to striated duct via myoepithelial cells contracting the acinus end, moving contents towards striated duct.
81
Tight junctions of acinar cells vs ductal cells
Acinar cells have leaky tight junctions, allowing for passage of water and small ions while ductal cells do not allow water to pass
82
Why is the primary secretion of saliva isotonic?
Because there is no limit on how much water and sodium pass through the leaky acinar tight junctions.
83
Parasympathetic pathway for regulation of salivary gland function..how is it stimulated? How can it be inhibited?
Dominant regulatory pathway
Stimulated by smell/taste of food, or pressure receptors in mouth, or during nausea
Can be inhibited by tiredness, fear, fatigue
84
Sympathetic pathway for regulation of salivary gland function..how is it stimulated?
Minor pathway
Increases saliva flow
Increases protein secretion from acinar cells and stimulates myoepithelial cells to contract to increase flow
85
Amylase
Enzyme found in saliva that breaks down starch
| Can only break alpha-1,4 linkages
86
Plant starch is made up of?
Glucose polymers amylose and amylopectin
87
Amylose
Straight chain of glucose polymers with alpha-1,4 linkages
88
Amylopectin
Chain of glucose polymers with both alpha-1.4 and 1,6 linkages
89
Breakdown of amylose creates?
Maltose and maltotriose
90
Breakdown of amylopectin creates?
Maltose, maltotriose, and alpha limit dextrin due to the alpha 1,6-linkages not being broken
91
Lingual lipase
Breaks down fats , can remain active in stomach
92
When are amylase and lingual lipase especially important?
When there are conditions of reduced pancreatic activity (digestive enzyme secretion)
93
Xerostomia
Dry mouth
94
Conditions where saliva secretion is impaired?
Congenital
Schogrens disease- Autoimmune dieases where immune system attacks salivary glands
Drug side effects
Radiation therapy
95
Consequences of salivary gland impairment?
```
Decreased oral pH
Tooth decay
Dry mouth
Esophageal erosions due to no saliva being able to neutralize stomach acid coming up esophagus
Difficulty chewing/swallowing food
```
96
Treatment for impaired salivary production?
Frequent sips of water
| Fluoride treatment for bacteria
97
How is swallowing initiated?
Pressure receptors in the pharynx stimulated by presence of food or liquid entering pharynx
98
Pharynx
Tube at the back of esophagus common to food and air
99
Larynx
Between pharynx and trachea containing vocal chords; voicebox
100
Glottis
Area in larynx around vocal chords where air can pass
101
Epiglottis
Cartilage flap that closes to prevent food from entering lungs
102
Process of swallowing
Chew food
Food moves to back of throat
Soft palette elevates to prevent food from going up nose
Respiration inhibited by impulses from swallowing centre
Larynx raised, epiglottis closes and covers trachea
Food enters esophagus
103
Esophagus anatomy
Mucus is secreted
| Stratified squamous epithelium
104
Stratified vs squamous
```
Stratified= in layers
Squamous= flattened
```
105
Upper esophageal sphinctor
Ring of sketal muscle located below the pharynx
106
Lower esophageal sphinctor
Ring of smooth muscle located where the esophagus joins the stomach.
107
When are esophageal spinctors closed?
Always closed, except for when swallowing, vomiting, or burping,
108
Heart burn causes
Lower esophageal sphincter not closing properly
Big meal
Pregnancy
109
Stomach functions
Storage of food
| Chemical and mechanical breakdown of food
110
Pepsinogen
Secreted by the stomach, and cleaved to form enzyme pepsin
111
Pepsin
Enzyme that initiates protein digestion in stomach
112
HCl
Secreted in stomach, and helps break down macromolecules in food.
Partial sterilization of food
113
Intrinsic factor
Secreted by stomach
| Essential for absorption of vitamin B12 in iliem
114
Fundus and body & what do they secrete?
Both have a thin layer of smooth muscle
Mucus
HCl
Pepsinogen
115
Antrum and what does it secrete?
Has a thicker layer of smooth muscle
Mucus
Pepsinogen
Gastrin
116
Pyloric sphincter
Controls emptying of the stomach
117
Endocrine vs exocrine
Exorcrine chemical messenger requires passage through blood , while exocrine involves secretion into ducts and then directly onto epithelial surface
118
Mucus
Protects the stomach epithelium from digestive enzymes and acid
119
Gastrin
Important in stimulating HCl production and stomach motility
120
Histamine
Stimulates HCl production
121
Somatostatin
Inhibits HCl production
122
Mucous cell
Located at luminal end of gastric gland
| Secretes mucous
123
Parietal cell
Located in fundus
| Secretes intrinsic factor and HCl
124
Chief cell
Found in gastric glands
| Secretes pepsinogen
125
Enteroendocrine cell/G cell
Found in gastric glands in antrum
| Secrete gastrin
126
Enterochromaffin-like cell
Found in gastric glands
| Secretes histamine
127
D cell
Found in gastric glands
| Secretes somatostatin
128
Canaliculi
Increase SA of cells to maximize secretion
129
Na/K ATPase
Primary transport
| 3 Na out, 2 K into cell for every molecule of ATP
130
H/K ATPase
Primary transport
Pumps out a proton (H) into lumen
Cell becomes more basic
131
Carbonic anhydrase
Parietal cell gets rid of base by removing bicarbonate
Catalyzes formation of carbonic acid from h20 and co2
Carbonic acid dissociates into H and bicarbonate
132
Cl/HCO3 exchanger
HCO3 is pumped out in exchange for Cl ion
| Secondary active transport
133
4 chemical messengers that regulate insertion of H/K ATPase into membrane?
Gastrin
Histamine
ACH
Somatostatin
134
Advantage of having inactive precursor?
Prevents autodigestion
135
3 phases of gastric secretion?
Cephalic phase
Gastric phase
Instestinal phase
136
Cephalic phase & how is acid secreted?
Brain is stimulated by sight, smell, or taste of food which provides excitatory stimulation via vagus nerve to the stomach
Vagal nuclei in brain cause parasympathetic nerve to release ACH at parietal cells and acid is secreted
137
Gastric phase & how is acid secreted?
Occurs when food reaches the stomach
Stimulated mainly by presence of food causing G cells to release gastrin into blood.
Gastrin interacts with parietal cell to increase acid production
138
Intestinal phase & how is acid secreted?
Occurs when partially broken down food from stomach enters SI
INHIBITORY phase due to presence of fat, acid, digestion products (slow digestion is wanted so phase is inhibitory)
Mediated by secretin and CCK, which have a negative influence on gastrin production
139
3 ways ACH can stimulate acid secretion at parietal cell?
1. Stimulates ECL cells to release histamine
2. Inhibits somatostatin production in D cells
3. Stimulates G cells to produce gastrin
140
In what way does gastrin stimulate acid secretion at parietal cell?
1. Stimulates ECL cells to release histamine
141
What happens once acid secretion is happening at a high rate?
ACH released from parasympathetic nerves and the stimulation is reduced as acid is produced and as you are eating.
Acid produced has an inhibitory effect on gastrin release from G cells
142
Somatostatin inhibits what?
Gastrin release from G cells
| Histamine release from ECL cells
143
Peristaltic waves
Weak contractions in the stomach
144
Pyloric sphinctor & what happens when it closes?
Located between antrum of stomach and duodenum.
| When it closes, some food is able to enter the duodenum, but most is retained in stomach for further digestion.
145
What determines strength of contraction?
Amount of stimulus
146
What determines the frequency of contraction?
Basic electrical rhythm
147
Causes of vomiting?
Psychogenic (you think of something like a food and its triggered)
Ear infection (motion sickness)
GI disturbances
Pressure in CNS
Chemoreceptors in GI tract and brain detect toxins
148
Where is the vomiting centre?
Medulla oblongata
149
What mechanisms happen when vomiting centre is stimulated?
```
Increased saliva production
Breath held in mid-inspiration
Nausea
Glottis closes off trachea
Lower esophageal sphinctor and esophagus relax
Diaphragm and abdominal muscles contract
Reverse peristalsis
```
150
Consequences of vomiting
Dehydration
Electrolyte imbalance
Metabolic alkalosis-elevated pH of a tissue due to acid lost
Tooth enamel erosion from acid
151
Peptic ulcer
Erosion of GI tract mucousa
| Can occur in stomach, esophagus or duodenum
152
Causes of ulcers?
Imbalance of aggressive factors (pepsin and acid) and protective factors (mucus and bicarbonate)
Infection from bacterium Helicobacter Pylori
Non-bacterial factors like smoking, excessive alcohol, drugs that reduce prostaglandin production
153
Ulcer treatment
Antibiotics
H/K pump inhibitors
Histamine receptor antagonists
Prostaglandin type drugs
154
Gastric bypass surgery
Stomach is divided into a smaller pouch which connects to SI, limiting how much food is absorbed. Used to weight loss
155
Is the stomach essential for life?
No, but complications can arise
156
Consequences of having stomach tied off or removed?
Intrinsic factor cannot be secreted without a stomach, so people must get vitamin B12 injections to prevent anemia.
Stomach is useful in reducing amount of bacteria that enters system
Sterilizes food
157
Exocrine pancreas and function
Secretes substances into ducts that drain onto spithelial surface
Important for digestion
Source of majority of enzymes needed for digestion of carbs, fats, proteins etc
Secretes bicarbonate into duodenum
158
Endocrine pancreas
Ductless gland
Secretion occurs over epithelial basolateral surface for diffusion into blood
Not important in digestion but important in producing hormones regulating the body
159
Sphincter of Oddi/hepatopancreatic sphincter
Common to the bile duct and main pancreatic duct
| Regulates the release of pancreatic and liver contents into SI
160
Pancreatic islets
Produce insulin
161
Acinar vs ductal cells within pancreatic ducts
Acinar- produce and secrete digestive enzymes
| Ductal- secrete bicarbonate
162
Pancreatic juices
Isotonic and alkaline due to bicarbonate
| Contains digestive enzymes and proteolytic enzymes which are stores and secreted in inactive forms
163
CFTR
Cl channel
Cystic fibrosis transmembrane conductance regulator
Allows Cl to diffuse out of duct cell into lumen
164
Ductular cell secretion of HCO3 steps
1. CFTR channels open and Cl diffuses into lumen
2. Cl in lumen exchanged for HCO3 in cell (HCO3 movies out)
3. Neutral pH maintained by exchange of H moving out for Na moving in (secondary active transport)
165
What happens after a meal?
Acid enters lumen of stomach
| Base bicarbonate leaves via blood
166
"The tide"
Anything moving into blood
167
In the stomach what happens to acid and base?
Acid moves into stomach lumen. Base moves into the blood.
168
In the pancreas what happens to acid and base?
Base moves into lumen, acid moves into blood.
169
Why is the pancrease essential to digestion?
Source of major enzymes requried for digesting carbs, fats, proteins, etc
170
Proteases
Enzymes that digest proteins into peptides and amino acids
171
Amylolytic enzymes
Digest starches into sugars
172
Lipases
Digest triglycerides into monoglycerides and free fatty acids
173
Nucleases
Digest nucleic acids into free nucleotides
174
How are enzymes packaged and where are they stored?
Packaged by the pancreatic acinar cells as proenzymes in zymogen granules
Stored at the apical pole of the acinar cell
175
Zymogens
Inactive precursor molecules
176
Enterokinase
Cleaves a pro-protease called tripsinogen into the protease trypsin
177
4 major proteases secreted by pancreas?
Trypsinogen
Chymotrypsinogen
Pro-elastase
Pro-carboxypeptidase A & B
178
Amylolytic enzymes? (1)
Pancreatic amylase
179
Lipolytic enzymes? (3)
Lipase
Phospholipase A2
Cholesterase
180
Trypsinogen: activated by? Active enzyme? Action? End products?
Enterokinase
Trypsin
Hydrolyzes peptide bonds
Peptides and amino acids
181
Chymotrypsinogen: activated by? Active enzyme? Action? End products?
Trypsin
Chymotripsin
Hydrolyzes peptide bonds
Peptides and amino acids
182
Pro-elastase: activated by? Active enzyme? Action? End products?
Trypsin
Elastase
Hydrolyzes peptide bonds
Peptides and amino acids
183
Pro-carboxypeptidase A&B: activated by? Active enzyme? Action? End products?
Trypsin
Carboxypeptidase A&B
Hydrolyzes bonds at C-terminal
Peptides and amino acids
184
Pancretic amylase ? Action and end products?
Cleaves starches to sugars
| Maltose, malitriose, alpha limit dextrins
185
Lipase? Action and end products?
Hydrolyzes triglycerides
| Free fatty acids and 2-monoglycerides
186
Phospholipase A2: Inactive enzyme? Activated by? Action and end products?
Prephospholipase A2
Trypsin
Hydrolyzes phospholipids
Free fatty acids and lysophospholipids
187
Cholesterolesterase? Action and end products?
Hydrolyzes cholesterol esters
| Free fatty acids and cholesterol
188
S-cells role
Produce secretin when acid enters duodenum from stomach
189
Secretin
Hormone that stimulates release of bicarbonate
190
I-cells role
Release CCK when fats and protein enter upper SI from stomach
191
CCK
Hormone that stimulates release of digestive hormones
192
Circulating secretin stimulates?
Pancreas and liver duct cells to increase bicarbonate secretion
193
Secretin and CCK bot inhibit what? What does this result in?
Both inhibit gastric secretion, which results in slowed stomach motility and reduced acid secretion
194
Which channel is mutated in cystic fibrosis?
The Cl channel involved in HCO3 secretion
195
Cystic fibrosis
Defective Cl channel
Enzymes do not get flushed from the ducts and never reach the intestine
Retained proteolytic enzymes can result in autodigestion
Patients must recieve supplements of digestive enzymes and antacids
196
People with cystic fibrosis can still produce what?
Digestive enzymes
197
Gallbladder
Sac located under liver
198
Bile ducts
Run from the liver and join to form the common hepatic duct which then joins with the common bile duct
199
Hepatic lobule and structure
Functional unit of the liver
| Has a hexagonal structure and central vein running through centre and a portal triad in each corner
200
Portal triad structure
Consists of a hepatic artery, hepatic portal vein, and a bile duct
201
Hepatocytes
Epithelial cells of the liver that form canalicular networks
| Produce and secrete bile acids
202
Canalicular networks
Tube like structures that join together until they form bile ducts
203
Bile components produced by hepatocytes are put into what?
Canalicular networks, and then flow towards bile ducts
204
Blood flow occurs where?
Other side of the hepatocyte
205
Major functions of the liver?
Detoxifying blood
Formation and secretion of bile
Metabolizing and storing nutrients
Producing circulating proteins
206
Bile
Breaks down fat
207
6 components of bile
```
Bile acids
Cholesterol
Salts
Phospholipids
Bile pigments
Trace metals
```
208
Bile acids
Made from cholesterol
| Emulsification of fats
209
What enzyme does bile work with to digest fat?
Pancreatic lipase
210
Emulsification
Large fat droplets being made smaller
211
What does emulsification require?
Mechanical disruption
| Emulsifying agent to keep droplets from re-agreggating
212
2 things in bile that help with emulsification?
Amphipathic bile acids and phospholipids
213
Micelle and function?
Polar heads facing outside while non polar tails facing inside in a circular formation
Allows easier absorbtion, increased SA for more absorption
214
Bile duct cells
Add bicarbonate, water and other salts to the bile
215
Basic steps of bile acid recycling
1. Bile acids released by liver/gallbladder into duodenum (from hepatocyte to bile)
2. Reabsorbed in SI into portal circulation
3. Transported back into hepatocytes from blood
216
Bile acids are synthesized where?
In hepatocytes
217
How are bile acids transported across apical surface?
Primary active transport in canalicular networks
218
How are bile acids absorbed across epithelial cells in SI?
Na dependant secondary active transport pathway
219
How is bile moved to blood?
Facilitated
220
How is bile acids in blood moved into hepatocytes
Secondary active transporter
221
How can foods high in fiber reduce cholesterol?
These foods bind to bile acids and are excreted in feces, preventing reabsorption of bile acids
222
How do bile salts regulate hepatobiliary secretion?
As more bile salts are absorbed by iliem and returned to liver, more will be secreted into bile
223
How does secretin regulate hepatobiliary secretion?
Increases bicarbonate secretion in bile ducts and in pancreas, stimulated by acid in duodenum
224
How does CCK regulate hepatobiliary secretion?
Production stimulated by digested fats and proteins in upper SI. Increases contraction of gallbladder and relaxes spincter of Oddi causing bile release into duodenum.
225
Cause of gallstones?
Excess cholesterol.
| If concentration of bile becomes too high relative to bile acids, cholesterol will precipitate out
226
Pigment stones?
Amount of bile pigments are increased due to excess RBC breakdown. Bile forms precipitates with Ca.
227
Gallstones consequences?
Obstruction or infection of gallbladder, pancreas, or liver
| Pain, nausea, jaundice, insufficient absorption of fats, and fat soluble vitamins
228
Gallstones treatment options?
Cholecystectomy (removal of gallbladder)
Removal of stones
Drugs to dissolve stones
229
Duodenum functions
Mixing of pancreatic digestive enzymes and bile with food
Absorption of nutrients
Release of CCK and secretin
230
Jejenum functions?
Digestion and absorption continued
231
Ileum functions?
Absorption of bile acids and vitamin B12
232
Folds of Kerckring?
Circular folds...essentially the whole intestine is folded on itself
233
4 epithelial cell types derived from stem cells?
Paneth
Endocrine
Absorptive/enterocytes
Goblet
234
Paneth cells
Secrete antibacterial peptides
235
Endocrine cells
Hormone producing cells (S and I cells)
236
Goblet cells
Secretion of mucus
237
Absorptive/enterocytes
Contain microvilli at apical surface of cell
238
Brush border
Microvilli covering villi of SI; major absorptive surface
239
Brush border enzyme
Anchored to the brush border with catalytic activity in the lumen
240
Only form of carbohydrates that can be absorbed is?
Monosaccharides
241
Sucrose
Glucose+fructose
| Broken down by sucrase
242
Lactose
Glucose+galactose
| Broken down by lactase
243
Monosaccharides that can be absorbed by GIT?
Glucose,fructose,galactose
244
How do glucose and galactose move from lumen of SI to enterocytes?
Use Na dependent glucose transporter (secondary active transport)
Uses the Na gradient to drive uptake of sugar into enterocyte
Na gradient generated by Na/K ATPase
245
How are glucose and galactose transported across the basolateral surface of enterocyte?
Use a Facilitated glucose transporter GLUT
246
How does fructose move into the enterocyte?
Using a facilitated carrier GLUT5
247
How is fructose transported across the basolateral surface of enterocyte?
Using facilitated glucose transporter GLUT2
248
Carboxypeptidase
Pancreatic protease
249
Aminopeptidase
Brush border enzyme
250
Small peptides can be taken up by?
Secondary active transport coupled to H
251
Large fat droplets are mostly composed of?
Triglycerides
252
Pancreatic lipase can only act on? Why?
The surface of fat droplets because it is water soluble.
253
What must happen in order for pancreatic lipase to act?
Fat droplets must be broken down into smaller ones
254
What prevents re-aggregation?
Bile acids and phospholipids that bind to the outside of the smaller droplets
255
As micelles break down they release what?
Fatty acids and monoglycerides
256
Once epithelial cells absorb fatty acids and monoglycerides, what happens?
They are processed by the ER and converted back into triglycerides.
This is to maintain the diffusion gradient of the lumen of the SI to the epithelial cell, so that fatty acids and monoglycerides can be absorbed into the enterocyte via diffusion.
257
Chylomicrons
Extracellular fat droplets absorbed by lacteals
258
Lacteal
Lymphatic vessel in the intestinal villi
259
Ferritin
Protein iron complex that acts as a storage form of iron
260
When body stores of iron are high what happens?
Increased production of ferritin, so increased binding of ferritin in epithelial cells, and reduction of amount of iron released into blood
261
What happens when there is a need for iron but the stores are depleted?
Decreased production of ferritin, so decreased retention in enterocyte, and more will be absorbed in blood rather than stored.
262
Iron toxicities
Genetic defects in absorption control pathways
Poisoning
Excessive intake of supplements
263
Iron deficiency anemia & causes?
Reduced number or size of RBC
| Caused by not enough iron in diet, blood loss, poor iron absorption, intestinal diseases
264
Why is fluid crucial in intestine?
Allows for contacts of food and digestive enzymes
Prevents damage of epithelium
Allows diffusion of digested nutrients to absorption site
265
Where is the most fluid absorbed?
Small intestine
266
Gradient direction for absorption vs secretion?
Inward direction for absorption, outward for secretion
267
3 important electrolytes for water absorption?
Chloride, bicarbonate, sodium
268
Absorption predominantly depends on ?
Na gradient
269
Absorption of water in SI?
Na gradient of Na/K ATPase end up moving glucose into cell
Glucose and Na are brought in via SGLT and pumped out by Na/K ATPase
Cl follows Na and water follows them
270
Secretion predominantly depends on?
Cl gradients
271
Secretion of water in SI?
NKCC1 allows accumulation of Cl in enterocyte based on inwardly directed Na gradient
CFTR opens allowing Cl to enter intestinal lumen
Na follows Cl, and water will follow, being secreted into the lumen
272
MMC and purpose?
Migrating myoelectric complex; referring to peristaltic activity.
Purpose is to move undigested material from SI to LI and prevents bacteria from staying in the SI
273
Regulation of MMC?
Hormone motilin initiates MMC. Motilin release is inhibited when you eat to allow for segmentation
274
Lactose intolerance
Cannot completely digest lactose. Results in decreased water absorption, gas, diarrhea
275
Lactose intolerance solutions?
Take a lactase pill with meal, or drink lactose free milk pre treated w lactase
276
Cholera
Caused by consuming bacteria Vibria Cholera in contaminated food or water. Causes vomiting and diarrhea
277
What does the bacteria in cholera produce?
Toxin that increases production of cAMP
This causes Cl channel to open allowing large amounts of Cl into intestinal lumen, and water follows and is lost as diarrhea
278
Cholera treatment?
Consume clean water with salts and glucose to replace fluids
279
Ileocecal valve. When is it open/closed?
```
Between cecum (appendix) and illeum
Open after a meal when ileum contracts, closed when LI is distended. Retains LI contents
```
280
Colon functions?
Reabsorption of water
Reservoir for waste and undigested products prior to defecation
Absorb products of bacterial metabolism
281
Internal vs external anal spinctors?
Internal- smooth muscle, involuntary
| External- skeletal muscle, voluntary
282
Important difference between SI and LI? Results in?
LI has no villi while SI does. Results in lower SA in LI.
283
Absorptive cells in LI compared to SI?
Do not contain brush border enzymes in LI
284
Process of defecation?
Rectum distends and activates mechanoreceptors
Rectum contracts, internal anal sphinctor relaxes while external contracts initially
Then vice versa occurs and feces voided
285
7 functions of the respiratory system?
```
Provides oxygen to tissues
Eliminates CO2
Filters and protects from microbial infections
Helps regulate blood pH
Phonation (speech formation)
Olfaction
Blood reservoir
```
286
Alveoli
Fundamental units of the respiratory system and contain lots of capillaries
287
Pharynx is split into what 2 components?
Nasopharynx and laryngopharynx
288
What happens to allow phonation?
Air travels through vocal cords in larynx
289
Air passage pathway
Larynx, trachea, 2 primary bronchi, lungs
290
Trachea and primary bronchi can characterized by what?
Semi-cartileginous C shaped ring and smooth muscle in back.
| Protects and promotes elasticity
291
Bronchi
Same cartilage sturctures as primary bronchi but not C shaped, rather plate shaped
292
2 divisions of the tracheobronchial tree
Conducting zone and respiration zone
293
Conducting zone, and what does it consist of?
Anatomically dead space where there are no alveoli so no gas exchange occurs.
Consists of the trachea, primary bronchi, bronchioles and terminal bronchioles
294
Respiratory zone, and what does it consist of?
Further down and contains the alveoli where gas is exchanged.
Contains respiratory bronchioles, alveolar ducts, alveolar sacs
295
Terminal bronchioles
Smallest airways WITHOUT alveoli
296
Respiratory bronchioles
Occasional alveoli
297
Alveoli sacs
Contain large number of alveoli
298
Type I alveoli
Flat cell, lined with fluid containing surfactant.
| These cells do NOT divide
299
Type II alveoli and its functions
Not frequently found.
Produce surfactant
Can act as progenitor cells, so they can replicate into type I alveoli cells which cannot be replaced on their own
300
Surfactant importance
Important for respiratory function
301
How do O and CO2 diffuse through the respiratory membrane?
O diffuses from alveoli to blood stream
| CO2 diffuses from blood to alveoli
302
Pnueumocyte
Referring to either type I or II alveolar cells
303
Ventilation
Movement of gas from atmosphere to alveoli by bulk flow
304
Movement of gas is due to what?
Changes in pressure and volume; promotes movement of gas from area of high to low pressure
305
5 steps of respiration
Ventilation
Exchange of O and CO2 between alveoli and blood by diffusion
Transport of O and CO2 through pulmonary and systemic circulation by bulk flow
Exchange of O and CO2 between blood in tissue capillaries and cells in tissues by diffusion
CO2 produced and O used by cells
306
How is airflow produced?
Motor neurons innervate respiratory muscles by CNS stimulation.
Respiratory muscles contract
Thoracic volume, thoracic pressure, and intrapulmanory pressures change with contaction and relaxation, allowing for gas movement in/out
307
3 categories of muscles involved in respiration?
Pump muscles, airway muscles, accessory muscles
308
Pump muscles
Make changes in pressure and volume at lung level
309
Inspiratory vs expiratory pump muscles
Inspiratory- active during inspiration.
| Expiratory- active during expiration
310
Airway muscles
Keep airways open
311
Accessory muscles
Facilitate respiration when there is an increased metabolic drive; ex used only when exercising pretty much
312
Main inspiratory muscles?
Diaphragm
External intercostals
Parasternal intercostals
313
Main expiratory muscles?
Internal intercostals
314
Diaphragm, and what happens when it contracts?
Dome shaped structure, separates the lungs from the abdominal content.
When it contracts, it moves down, allowing rib cage to move up and out (widening) so overall INCREASE in thoracic volume
315
External intercostals and their motion?
Help contract and lift rib cage
| Bucket handle motion
316
Parasternal intercostals and their motion?
Contract and pull sternum forward
| Pump handle motion
317
When are inspiratory muscles active?
All the time during inspiration
318
When are expiratory muscles active?
Only during the expiratory phase of when you are MAKING AN EFFORT to breath out, so during stress, coughing, exercise. They do not contract during expiration at rest
319
Internal intercostals
Used during forced expiration
| Push rib cage down to reduce thoracic volume
320
Inspiration at rest vs during deep breathing/exercising
At rest: diaphragm contracts expanding thoracic cavity
Deep breathing: stronger contraction of diaphragm, as well as recruitment of accessory muscles to allow further expansion of thoracic cavity
321
Expiration at rest vs forced
At rest: abdominal and intercostal muscles are not active
Forced: abdominal muscles contract strongly causing diaphragm to move up and expel even more air
Internal intercostal muscles contract to move rib cage down
322
What factors occur in someone with obstructive sleep apnea?
Depressed muscle tone of muscles in upper respiratory muscles
Reduction of openness in airway, resulting in snoring and large drops of O saturation in blood
323
Why does sleep apnea occur?
Problem with neural control of breathing
| Lack of excitatory drive which is needed to maintain tone
324
Consequences of sleep apnea
Daytime fatigue
Changes in O saturation (resulting in cognitive impairment)
Cardiovascular risks
325
How to treat sleep apnea?
No drug treatments but can administer a mask that delivers constant positive airway pressure and keeps upper aiways open.
326
2 regions involved in filtering action?
Conducting zone (muco-ciliary escalator) and at the level of alveoli
327
2 types of cells lining the surface of trachea. Function?
Goblet cells
Ciliated cells
Role is to entrap inert or biological particulates that were inhaled and remove them from airways.
328
Ciliated cells
Have cilia on apical surface. Produce periciliary fluid
329
Goblet cells
No cilia, produce mucus
330
Periciliary fluid
Low density fluid produced by periciloary cells which allows cilia to move freely.
331
SOL layer
Layer of perciliary fluid sitting on top of the ciliated cells
332
Gel layer
Thick layer of mucus produced by goblet cells, distrubuted in patches
333
What changes can affect the muco-ciliary layer?
Changes in thickness of the SOL or gel layers
334
Smoking effect on goblet and ciliary cells?
Decreases ciliary cells activity, increase goblet cells
335
What happens when silica or asbestos are inhaled? What condition can occur and why?
Macrophages recognize them as foreign objects and phagocytose them, but cannot digest them.
Silica and asbestos kill the macrophages and chemotactic factors are released.
Promotes fibroblasts into alveoli
Increases collagen which promotes lung stiffness, so pulmonary fibrosis can occur
336
Spirometry
Test that determines the amount and rate of inspired and expired air
337
Tidal volume
Volume of air breathed (in OR out) during one cycle
338
Expiratory reserve volume
Amount of additional air that can be expired by forcibly exhaling to the max
339
Inspiratory reserve volume
Amount of additional air that can be inspired by forcibly inhaling to the max
340
Residual volume
Amount of air left in lungs after maximum expiration; cannot be expired even forcibly
341
Vital capacity
Maximal volume of air that can be exhaled after maximal inspiration
VC= TV+IRV+ERV
342
Inspiratory capacity and formula
Maximal volume of air that can be inhaled`
| IC= TV+IRV
343
Functional residual capacity and formula
Amount of air remaining in lungs after normal expiration
| FRC= RV+ERV
344
Total lung capacity
Amount of air in lungs after maximal inspiration
| TLC= TV+IRV+FRC= VC+RV
345
What cannot be measured by spirometry?
Residual volume
| Also cannot measure any capacity with RV in the formula, therefore FRC and TLC cannot be measured using spirometry
346
Total or minute ventilation
Amount of air exchanged within a minute or within a rate time
347
How to calculate total or minute ventilation?
Respiratory frequency x tidal volume
348
Alveolar ventilation
Amount of air moved into the alveoli per minute
349
How to calculate alveolar ventilation?
Subtract the anatomical dead space volume from the tidal volume and multiply by the respiration frequency
350
What kind of breathing is more effective in increasing alveolar ventilation? Why?
Deep breathing, as majority of the minute ventilation is dedicated for gas exchange
351
FEV-1
Forced expiratory volume in one minute; how much of the vital capacity volume can be expelled in 1 min
352
FVC
Forced vital capacity; same as vital capacity test
353
3 factors looked at in spirometry tests
1. FEV-1
2. FVC
3. Ratio of FEV-1/FVC
354
Obstructive lung disease. Due to what? Obstructive pattern is common in patients with..?
Difficulty exhaling all the all from their lungs
Due to lung damage or narrowing of airways
Common in people with cyctic fibrosis, asthma
355
Obstructive lung disease effect on FEV-1, FVC, and ratio?
FEV-1 reduced
FVC reduced or normal
Ratio reduced
356
Restrictive lung disease. Due to what? Restrictive pattern is common in patients with..?
Difficulty filling lungs fully with air.
Lungs restricted from expanding due to condition causing lung stiffness.
Common in people with lung fibrosis, neuromuscular disease, scarring in lung tissue
357
Restrictive lung disease effect on FEV-1, FVC, and ratio?
FEV-1 reduced (since amount of air inhaled is less than usual, amount exhaled will be less, even though one has the full ability to expel air )
FCV reduced
Ratio normal, but volume is less
358
Helium dilution method?
Used to measure FRC
359
Helium dilution method only measures what?
Communicating gas or ventilated lung volume
360
2 classes of properties of mechanisms of ventilation?
Static and dynamic
361
Static
Properties that are present when no air is flowing
362
Dynamic
Properties that are present when the lungs are changing volume and air is flowing in/out
363
Boyle's law
At a contant temp, pressure and volume and inversely proportional
(increase in V=decrease in P)
364
How does gas flow?
Bulk flow, from an area of high pressure to area of low pressure
365
Pressure during inspiration
Thoracic cavity volume increases and pressure decreases, so air moves from an area of higher pressure (environment) to low pressure (alveoli)
366
Pressure during expiration
Thoracic cavity volume decreases, so pressure increases so air moves from alveoli to environment (lower pressire)
367
Visceral pleura
Covers surface of the lungs
368
Parietal pleura
Attached to the inner surface of the thoracic cavity
369
Interpleural fluid
Separates the visceral and parietal pleura, allowing them to slide around during inspiration
370
Why do lungs have the tendency to collapse?
Elastic recoil
371
What happens at equilibrium of lungs and chest wall?
Inward elastic recoil of lungs balances out the outward elastic recoil of the chest wall
372
How do lungs and chest wall interact?
Through the interpleural space between visceral and parietal pleurae.
373
Intrapleural pressure
Pressure inside the pleura
374
Alveolar pressure
Pressure inside the alveoli
375
Transpulmonary pressure
Difference of the alveolar pressure minus the intrapleural pressure
376
Intrapleural pressure is always what?
Negative (or subatomic) because of the opposing forces of elastic recoil
377
What occurs when someon has a collapsed lung in terms of pressures?
The alveolar pressure and intrapleural pressure are equal
378
Which pressure is static and determines lung volume?
Transpulmonary pressure
379
Which pressure is dynamic and determines air flow?
Alveolar pressure
380
Steps in inspiration
CNS sends excitatory signal to inspiratory muscles
Muscles contract and generate increase in thoracic volume
Increase in transpulmonary pressure
Increase in lung volume
Decrease in alveolar pressure
Air moves in
381
Steps in expiration
```
Relaxation of inspiratory muscles
Chest recoils (decrease volume)
Instrapleural pressure is back to normal so transpulmonary pressure is reduced
Increase in alveolar pressure
Air moves out
```
382
Forces that affect resistance to air flow?
Inertia of respiratory system
| Friction forces
383
Different friction forces
Friction between different alveolar sacs
Friction between lung and chest wall
Resistance that airflow incurs when entering airway
384
Laminar flow and where does it occur?
Subject invests little energy in airflow resistance
| Occurs at small airways that are distal to terminal bronchioles
385
Transitional airflow and where does it occur?
Takes extra energy to produce vortices, resistance increases.
Occurs at most of the bronchial tree
386
Turbulant flow
No longer smooth and laminar
| Found in larger airways such as trachea, larynx, pharynx
387
How does Poiseuille's Law relate to airflow resistance?
The smaller the radius of an airway, the more resistance
388
Where is resistance lowest? Why is this?
In the small airways. In this case, this is due to them being arranged in parallel. So, when calculating resistance it is INVERSE of each resistance, resulting in minimal resistance.
389
How to calculate resistance for airways arranged in parallel vs in series?
In parallel: sum of all the individual resistances
| In series: inverse of each resistance
390
How can small airways be occluded?
Contraction of smooth muscle
Edema (presence of fluids reduces space)
Mucus accumulation
391
Lung compliance
Measure of the elastic property of lungs and how easily lungs expand
392
Why is lung compliance considered to be a static and dynamic property?
Can be measured in the presence or absence of airflow
393
How is lung compliance determined on graph?
Transpulmonary pressure on x axis and lung volume on y axis. Lung compliance is the slope!
394
Pulmonary fibrosis: high or low lung compliance? Why?
Low. Patient has to make a big effort to breath in and increase transpulmonary pressure
395
Emphysema: high or low lung compliance?
High
396
Hysteresis
Difference in inflation and deflation compliance path
397
Why does hysteresis exist?
Because there is more pressure needed to open an airways rather than keep an airway open
398
Lung compliance is determined by?
Elastic components of lungs: elastin and collagen
| Surface tension at the air-water interface within alveoli
399
Where are elastin and collagen found?
In the walls of the alveoli, around blood vessels and bronchi
400
Emphysema, what occurs?
Many large alveolar spaces, compared to a healthy dense network of alveoli.
Elastin is decreased so floppy lungs occur.
Increased compliance in which little pressure is needed to cause large changes in volume.
401
Surface tension
Property that occurs at the interface between the surface and air in which attracting forces pull a liquid's surface molecules together. Decreases lung compliance
402
Role of surface tension in the lungs?
Type I alveolar cells come in contact with fluid that contains surfactant, and alveoli are lined with thin layer of fluid. Surface tension occurs at all fluid-air boundaries
403
Effect of surface tension?
To cause the surface to maintain as small of an area as possible
404
How does alveolar radius size affect amount of pressure needed to keep bubble inflated?
The smaller the radius, the more pressure needed to keep it open
405
Composition of surfactant
Mixture of phospholipids
Hydrophilic head dips into the water
Hydrophobic tail sits in the alveolar air
406
How does surfactant reduce surface tension? What does this result in?
Breaks strong attractive forces between water molecules at surface. Reduction in surface tension and increase in lung compliance making it easier to breath
407
In smaller vs larger alveoli, surfactant is found...?
Closer together in smaller, farther apart in larger alveoli
408
Functions of surfactant
Stabilizes alveoli
| Reduces surface tension
409
Why do premature babies have respiratory issues?
They don;t have enough surfactant in their lungs
410
Ventilation is lower/higher in what parts of the lung?
Higher in the lower part , lower in the higher part
411
How does gravity and posture affect ventilation?
Laying on your back, the highest ventilation is at the back of your lungs towards your back while the chest wall has less activity
412
Where is pressure more negative/less negative at? Why?
Gravity affects the pressure and since lungs have weight, the weight increases pressures meaning pressure in the lower part of the lung increases (becoming less negative since it is already negative) while the top part of the lung has decreasing pressure, meaning it becomes more negative
413
Dalton's Law
Each gas has its own specific pressure and the total pressure of a mixed gas is calculated by the sum of the individual pressures
414
Fick's Law
The rate of transfer of a gas is proportional to the membrane SA, and depends on the diff in partial pressures of the 2 environments. Inversely proprotional to thickness of membrane.
415
Diffusion constant
Amount of gas transferred between alveoli and blood per unit time.
Proportional to solubility of gas and inversely proportional to the square root of molecular weight.
416
Henry's Law
Amount of gas dissolved in a liquid is directly proportional to the partial pressure of gas in which the liquid is in equilibrium
417
Concentration of gas molecules in a liquid is determined by?
Partial pressure and solubility
418
Why is the PO2 in the air in alveoli lower than in atmosphere?
When air enters alveoli, lots is humidified resulting in increased PH20 and decreased PO2.
419
Determinants of alveolar PO2? describe.
PO2 in atmosphere- depending on altitude, high altitudes have lower pressures so the PO2 is reduce PROPORTIONALLY (still same percentages)
Alveolar ventilation- increase in alveolar ventilation means increase in gas exchange
Metabolic rate- exercising results in lower PO2 since it needs O2
Lung perfusion- changes in cardiac output change the amount of blood passing through resp system, which alters alveolar PO2
420
Determinants of alveolar PCO2?
PCO2 in atmosphere- when blood is in contact with respiratory membrane, large amount of CO2 diffuses to the alveoli, and alveolar PCO2 > atmospheric PCO2
Alveolar ventilation- decrease in alveolar ventilation means less exhalation of CO2 into atmosphere so PCO2 in alveoli > atmosphere
Metabolic rate- increase exercise increases CO2 production, so higher level of CO2 moving into alveoli to be exhaled
Lung perfusion
421
Why do we need pulmonary circulation to be a low pressure system?
Because the respiratory membrane is fragile, and high BP could damage it.
422
How is the respiratory system a high compliance system?
Thin walls allowing for small changes in pressure to result in large vessel expansion
423
Ventilation/perfusion ratio
Balance between ventilation (bringing O into/removing CO2 from alveoli) and perfusion (removing O from alveoli and adding CO2)
424
The greater the ventilation...?
The more similar PO2 and PCO2 will be similar to atmospheric pressures
425
The greater the perfusion...?
The composition of alvelor air at the region of higher perfusion will be more similar to the mixed venous blood with a reduction in PO2 and increase in PO2
426
High V/Q ratio is seen in what condition?
Collapsed lung or pleurisy
427
What happens in a high V/Q ratio physiologically?
Blood flow is occluded
| Very little gas exchange because theres no blood available
428
What happens to PO2 and PCO2 in alveoli in a high V/Q ratio?
PO2 increases because there is no oxygen that passes to the lungs through vasculature
PCO2 decreases because there is no CO2 delivered and diffuses from capillary system to alveoli
429
Alveolar dead volume
Region of lungs where there is a high V/Q ratio due to pathological condition. Region is over-ventilated and underperfused, therefore not contributing to gas exchange
430
Anatomical dead volume
Differs from alveolar dead volume; it is the conducting zone
431
Low V/Q ratio is seen in what condition?
Collapsed bronchi or bronchioles
432
What happens in a low V/Q ratio physiologically?
Airflow is obstructed/occluded
| No exchange of gas between alveolar air and atmosphere
433
What happens to PO2 and PCO2 in alveoli in a low V/Q ratio?
Increased PCO2 and decrease in PO2
434
Shunt
Portion of the venous blood that does not get oxygenated and is not available for gas exchange because of alveolar occlusion.
435
V/Q ratio is lower where?
Bottom of the lungs
436
PO2 and PO2 levels at top and bottom of lung if we have an ideal V/Q ratio?
At the bottom: slightly reduced PO2 and slightly increased PCO2
Top: reduced PCO2 and increased PO2
437
Bronchiocontriction in an alveoli. What happens to the pressures?
Makes diameter of airway smaller leading to a reduction in ventilation
PCO2 is increased, PO2 decreased
438
2 forms that O2 is carried in blood?
Dissolved in plasma
| Bound to hemoglobin (98%)
439
Hemoglobin structure
Protein made of 4 amino acid subunits called globins (2 alpha 2 beta) and 4 heme groups
440
Heme group
Porphyrin ring structure in which an iron atom binds to oxygen
441
What is an O2 dissociation curve?
Shows the interaction between hemoglobin and the arterial partial pressure of O2
442
2 properties highlighted in an O2 dissociation curve?
Oxygen capacity- max amount of O2 that can be combined with hemoglobin
Hemoglobin saturation- percentage of the available hemoglobin sites that have O2 attached
443
Factors that influence interaction between hemoglobin and O2?
Arterial PO2 (most important because as it changes, the saturation of hemoglobin changes)
pH
PCO2
Temp
444
Cooperative binding
Occurs because we have deoxyhemoglobin (hemoglobin with no O bound to it)
Leads to sigmoidal shape of O2 dissociation curve
445
Conformational changes in hemoglobin
After one O2 molecule binds, hemoglobin goes from a tense to relaxed state allow each consectuive O2 to bind more easily
446
Anemia vs polycythemia Hb amounts?
Anemia- low Hb levels
| Polycythemia- high Hb levels
447
How does O2 in alveoli move to RBC?
Pressure gradient established since PO2 is higher in alveolar space than in plasma, so O2 moves into plasma
Another pressure gradient is established where O2 molecules move from plasma to RBC where they bind to Hb.
448
How does O2 move from RBC to mitochondria in peripheral tissue?
Oxygen moves from RBC to plasma to interstitial fluid to space between cells to intracellular space to MIT
449
There is more O2 unloading if...?
There is a lower PO2 in peripheral tissue
450
What does a shift to the right of O2 dissociation curve mean?
For the same level of PO2, there will be a lower level of Hb saturation. It means that there is increased unloading of O2 since O2 affinity for Hb is reduced.
451
Factors causing a shift right
Increased temp
Increased PCO2
Anything that increases metabolism causes increased unloading of O2
452
Shift to left means?
Increased O2 affinity for Hb, less unloading
453
DPG
Present in RBCs and is an end product of RBC metabolism
| Shifts curve to the right
454
Is CO2 or O2 more soluble ?
CO2
455
3 ways CO2 is carried in blood?
Dissolved
Bicarbonate
Carbamino compounds
456
Carbonic acid rxn
CO2+H2O--->carbonic acid
457
Carbonic acid dissociates into?
H ions and bicarbonate
458
Chloride shift ad function?
Bicarbonate exits RBCs and Cl anions enter
| This functions to maintain the electrical neutrality in RBCs
459
How is caraminohemoglobin formed?
CO2 interacts with the globin chain of hemoglobin
460
CO2 has a higher affinity for...?
Deoxyhemoglobin (compared to oxyhemoglobin)
461
What happens to the curve if PCO2 increases?
Shift to the right and a lower percentage of Hb is bound to O2
462
H ions have a higher affinity for...?
Deoxyhemoglobin
463
2 major effects of hemoglobin and H interacting?
Unloading of O2- at lower pH there is reduced Hb saturation of O2 and ore unloading; shift right
Hemoglobin buffers the change in pH at level of venous blood
464
Respiratory acidosis
Hypoventilation (CO2 production > CO2 elimination)
| Increased PCO2 and H ion concentration
465
Respiratory alkalosis
Hyperventilation (CO2 production< elimination)
| Decreased PCO2 and H ion concentration
466
Metabolic acidosis
Increase in H ion concentration, independant of PCO2
467
Metabolic alkalosis
Decrease in H ion conc, independent of PCO2
468
3 regions in brain that control breathing?
Pontine, dorsal, and ventral respiratory groups
469
Where is breathing initiated?
Medulla
470
Where is breathing modified?
By higher centers in CNS and inputs from central and peripheral chemoreceptors and mechanoreceptors in the lung and chest wall
471
Why is ventral respiratory group the most important?
Contains the inspiratory and expiratory rhythm generator
472
Pre Botzinger complex
Inspiratory rhythym generator
473
Parafacial respiratory group
Groups of neurons within the ventral respiratory group
| Important in active contraction of abdonimal muscles
474
Where is rhythm of breathing initiated?
Ventral respiratory group in medulla
475
Factors influencing rate of breathing?
Neuromodulary factors (neurotransmitters)
Suprapontine influences that are emotional
Sensory inputs
476
Neuro respiratory pathway for inspiration
Pre Botzinger complex, inspiratory premotor neurons in VRG excited, excite phrenic and thoracic motor neurons, activate diaphragm and external intercostals
477
Neuro respiratory pathway for active expiration
pFRG geenrates rhythm, expiratory pre motor neurons excited, activate thoracic and lumbar motor neurons, activate internal intercostals and abdominals
478
2 peripheral chemoreceptors. What do they sense?
Carotid and aortic bodies. Sense changes in PO2, esecially hypoxia (decrease in PO2)
479
2 cell populations in carotid bodies
Type I glomus cells
| Type II sustentacular cells
480
Type I glomus cells
Chemosensitive
| Simialr to neurons and can genrate AP
481
Primary stimulus for peripheral chemoreceptors?
Decrease in arterial PO2
482
What happens in glomus cells when PO2 decreases?
Increased firing rate
483
When do we see a strong increase in minute ventilation?
Only when theres a drastic drop in PO2 levels, like in lung diseases or high altitude
484
Small increase in arterial PCO2 results in?
Very large changes in minute ventilation
485
Central chemoreceptors
Close to ventral surface of medulla
| Sense changes in PCO2
486
Hypercapnia
Too much CO2 in blood
