The digestive system- 1 Flashcards
1
Q
How does the digestive system contribute to homeostasis?
A
It transfers nutrients, water, electrolytes from external to internal environment. (This is also the function of the digestive system)
2
Q
True or False:
The digestive system directly regulates concentration of internal constituents.
A
FALSE
3
Q
Does the digestive system change water, nutrients or electrolyte uptake?
A
No
4
Q
The digestive system optimizes conditions for:
A
Digestion and absorption
5
Q
label
A
6
Q
GI system = ?
A
Gastrointestinal system (digestive system)
7
Q
What role does food play?
A
- Used by cells to generate ATP
- Source of building material for renewal and addition of body tissues
8
Q
is eaten food ready to be used by cells?
A
NO,
- Food must be digested (broken down) into simple molecules.
- SImple molecules must then be absorbed from GIT
- Then distributed via circulation to cells.
9
Q
What are the 4 main digestive processes?
A
- Motility (movement)
- Secretion (release)
- Digestion (breakdown)
- Absorption (uptake)
10
Q
Name and describe the two types of basic motility
A
1. Propulsive movements:
-Propel/push contents forward through the digestive tract
-Rate of propulsion differs from one region to another
(esophagus vs small intestine)
2. Mixing movements:
- Mix food
- Facilitate absorption
11
Q
What causes motility? are there any exceptions?
A
Smooth muscles, and yes…
Exceptions: Ends of GI tract- mouth and anus -Motility is caused by skeletal muscle
12
Q
Why is the mouth and the anus (motility) controlled by skeletal muscle?
A
For voluntary and involuntary reflexes
13
Q
Part of the respiratory passageway is located between the trachea and the pharynx. It keeps the airway open, prevents food from entering the airway, and produces sounds
A
The larynx
14
Q
Visceral smooth muscle; contracts as a unit, electrically coupled, often has spontaneous action potentials.
A
unitary smooth muscle
15
Q
Characteristic of smooth muscle to adapt to increased length and relaxation; stress-relaxation response
A
Plasticity
16
Q
Explain the motility in the mouth
A
- The mouth receives food into the GI tract.
- Chewing tears and grinds food, reducing lumps to a size that can be swallowed.- also mixes ingested food with saliva, moistening it enough to be easily swallowed.
Summary:
Type- chewing
Function-
Mechanical breakdown of food particles
Mixing food with saliva
17
Q
Chewing is part voluntary and involuntary…what sets the pattern and rhythm of chewing?
A
The cortex and brain stem centers
18
Q
True or false:
The esophagus serves a digestive or absorptive function.
A
False, it is simply a conduit between the pharynx and stomach
19
Q
What is the motility in the esophagus?
A
Peristalsis- a progressive wave of muscle contractions
20
Q
What initiates primary peristalsis?
A
Swallowing
21
Q
describe the motility of the esophagus
A
- Tongue separates a bolus
- Soft palate closes the nasopharynx
- The larynx rises and the glottis closes- to cover the trachea
- epiglottis falls to cover the closed glottis.
- Pharyngeal muscles contract and upper esophageal sphincters relax.
- Bolus enters the esophagus, and lower esophageal sphincters (LES) and stomach relax.
- Bolus moves toward the stomach
- Respiratory passages open ( everything reverts to normal)
- Bolus enters the stomach and LES closes-prevents regurgitation
22
Q
what causes the variations of the force of peristaltic contractions?
A
the size of the bolus
23
Q
stimuli from what is delayed to the CNS to modify the pressure generated by the esophageal muscles?
A
from the distention of the esophagus wall
24
Q
What happens if a bolus of food doesn’t progress all the way to the stomach?
A
Secondary peristalsis
25
describe what happens during secondary peristalsis:
1. The esophagus is distended
2. Afferent signals are relayed to the CNS
3. This leads to the second wave of peristaltic contractions.
26
Summarise what the motility is of the esophagus ( what it is and function)
-Primary and secondary peristalsis
Function=propel a bolus of food to the stomach
27
Name 3 functions of the stomach:
1. It stores food
2. Mixes food with gastric juice for digestion
3. Empties chyme into duodenum
28
What allows for different movements (which serve each function) of the stomach?
The muscular structures of the stomach wall.
29
what happens in the stomach during a swallow?
1. Receptive relaxation occurs in the fundus and body of the stomach.
2. Relaxation occurs with each swallow and permits the stomach to accommodate a volume of at least 1L with little increase in pressure.
3. Peristaltic contractions mix stomach contents and empty chyme into the duodenum.
4. The frequency of gastric peristaltic contractions is 3-5/min
30
Peristaltic waves begin \_\_\_\_\_\_\_\_\_\_\_\_, ripple over the body and become _______ over the muscular _________ and \_\_\_\_\_\_\_
Midstomach
Stronger
antrum and pylorus
31
What do antral contractions do?
They force chyme toward the duodenum and pulverize small lumps
32
Explain how food and gastric juice is mixed:
1. Antral contractions squirts a small amount of chyme through the constantly contracted pyloric sphincter with each powerful antral contraction.
2. As the contraction progresses, it closes the sphincter completely and most of the chyme is forced back into the stomach.
3. This retropulsion mixes the food and gastric juice.
33
Why does the volume and contents of the stomach regulate the strength of contractions?
Because the frequency of peristaltic contractions are constant
-The greater the volume, the more rapidly the contents are emptied.
34
What are the functions of the duodenum?
1. Regulates gastric emptying
2. regulates fat, acid, and hypertonic solutions in the duodenum
3. duodenal distention and slow gastric emptying
35
summarise the motility of the stomach:
**Motility:**
1. Receptive relaxation
2. Peristalsis
Functions:
1. Relaxation- accommodates meals
2. Peristalsis mixes and empties stomach content
36
What are the two types of secretion the digestive system produces?
exocrine and endocrine secretions
37
Specialized cells found in lining of GIT and accessory organs (pancreas)
release digestive juices when stimulated (neural or hormonal)
Exocrine glands
38
What are the digestive juices?
1. Water
2. Electrolytes
**3. Enzymes**
**4. Mucus**
**5. Bile salts**
**-→ organ specific**
39
What excretes enzymes
Exocrine glands
40
What excretes hormones
Endocrine glands
41
Describe exocrine glands
1. Larger component
2. Secretes 1.5-2L/day, rich in digestive enzymes
3. Has alkaline pH due to its content of NaHCO3
4. Produced by pancreatic acinar cells
42
Describe endocrine glands
1. Smaller component
2. COnsists of islets of Langerhans-4 cell types
3. Secretes 4 hormones
43
what 4 hormones do endocrine glands release?
Insulin
Glucagon
Pancreatic polypeptide
somatostatin
44
What are the 3 categories of energy-rich food?
Carbs
Proteins
Lipids
-Digestion is needed to break food down (from macromolecules)
45
What is the ratio of C:H:O in carbohydrates
1:2:1
46
How are most carbs classified as?
Mono-, di-, or poly-saccharide
47
Saccharide =?
Sugar
48
What are the building blocks (monomers) of all carbohydrates?
Monosaccharides
49
What are the three monosaccharides of carbohydrates?
Gluces
Fructose
Galactose
50
Which monosaccharide is the most abundant and what are some of its properties?
Glucose
- it is water soluble
- Easily transported through an organsm
- Energy source for cellular resp.
[Energy source for cells]
-
51
what is the main monosaccharide found in sugar of fruits?
Fructose
52
Galactose
Primary monosaccharide found in milk
53
What is the general monosaccharide formula?
C6H12O6
54
How are disaccarides forme?
When 2 monosaccharides are joined together via dehydration
-Forming glycosidic linkages
55
What are the three disaccharides?
Maltose
sucrose
lactose
56
Glucose + Glucose
Maltose= Malt sugar
57
Glucose + Fructose
Sucrose
=Table sugar
58
Glucose + Galactose
Lactose
=milk sugar
59
How are polysaccharides formed?
When glucose monomers link together to form long chains
60
What are polysaccharides ideal for?
Storing energy
61
Energy storage in plants
Amylose- straight chain
Amylopectin-Branched
62
Animal energy storage
Glycogen-highly branched chain
63
why is glycogen so branched?
To enable it to be broken down quickly to supply cells/tissue with energy
64
Polysaccharides which act as structural molecules?
Cellulose
chitin
peptidoglycan
65
Most abundant polysaccharide?
Cellulose
- straight chain
- found in cell walls of plants → adds strength
- it is a polymer of glucose, but it differs in configuration due to the bonds between each glucose unit.
- Most organisms cant break cellulose down, and thus, can't use it as an energy source
66
Polysaccharide which forms exoskeleton of insects and crustaceans?
Chitin
-Unique properties is due to chitin having amino groups attatched to its sugar monomers
67
complex polysaccharides found in cell walls of bacteria
Peptidoglycan
- Flexible and rugged due to its structure
- each monomer has a peptide chain attatched to it
68
Carbohydrates can be refered to as….
Simple sugars or complex carbohydrates
69
Monosaccharides and disaccharides?
Simple sugars
70
Polysaccharides
Complex carbohydrates
71
Amino acid structure
1. Carboxyl group [O=C-OH]
2. Amino group [N-H2]
72
What makes amino acids unique?
R group-gives amino acids properties
73
Order of amino acids in polypeptide chain
Primary structure
74
Pleated sheet/ helix- due to H bonding or other chemical reactions between the R groups or other chemical reactions of nearby amino acids
secondary protein structure
75
The overall shape of a polypeptide
Tertiary structure
- Secondary structure folds and twists upon itself
- then referred to as proteins
76
Interaction of multiple proteins= large protein complexes?
Quaternary structure
77
Hemoglobin and sodium channels in the cell membrane
Quaternary structure protein
78
Hydrophilic biomolecules
lipids
79
long term energy storage
The primary function of lipids
80
Hormone precursors, key component of cell membranes, protection, insulation, and lubrication
Other functions of lipids
81
4 basic groups of lipids
- Triglycerides
- phospholipids
- Steroids
- waxes
82
What do all lipids have in common
All insoluble in water
83
Fats-solid at room temp, used by animals.
Oils-Liquid at room temp, used by plants for long term energy storage.
triglycerides
84
Subunits of triglycerides
Glycerol and 3 fatty acids
85
3 parts of fatty acid
Acid group (OH)
Hydrocarbon chain
Methyl group (C-H3)
86
Single C-C fatty acid
Saturated fatty acid
87
Double bonds result in what
Kinks in the fatty acid chain affects melting point of fat
88
animal fats
saturated fatty acids
89
Veg oils
unsatturated
90
Trans fatty acid
when H bonds are on opposite sides of double bond
91
How do triglycerides form?
Through dehydration sysnthesis
92
- Glycerol and 2 fatty acids
- Phosphate group attached to 3rd carbon of glycerol
Phospholipids
93
4 fused rings of carbon- to which different functional groups are attached
Steroids
94
Precursor for the synthesis of other steroids:
Such as testosterone, estrogen, vit D, cortisone
Cholesterol
95
stabilizes plasma membrane
Cholesterol
96
difference between estrogen and testosterone
Testosterone has =O
Estrogen has -H
97
Nonpolar fats and repel water, are found in the outer coating on leaves and outer surfaces of animals.
Waxes
98
Occurs in the small intestine- in the ileum
Digestion
99
Digestion is incomplete
False
100
Where are digested substances transferred to?
From GIT to blood or lymph
101
finger-like projections found on the inner wall of the ileum
villi
102
Lymph vessel found in the middle of villi which is surrounded by a network of capillaries
Lacteal
103
water-soluble vitamins and minerals are absorbed where? and how?
through the walls of the villi, by diffusion and active transport
104
How is water drawn into the blood during digestion?
The absorption of digested food into the blood increases the water potential of the content in the ileum, water is drawn into the blood by osmosis.
105
Enter the epithelium of the villus by diffusion
Glycerol and fatty acid
106
what happens after glycerol and fatty acid are diffused into the epithelium of the villi?
They recombine into fine lipid droplets, which then enter the lymph in the lacteal
107
Lipid soluble vitamins are also absorbed into the lacteal
Vitamins A and D
108
What happens after everything has been absorbed by the villi?
Everything is transported to the main lymph vessels and then to the blood stream
