digestion

Question 1

what is the GIT?

Answer 1

alimentary canal that is continuous tube from the mouth to anus

Question 2

What is the main function of the GIT?

Answer 2

Conveys food along GIT allowing it to be broken down into small molecules which can be ansorbed in the circulation

Question 3

what is secretion?

Answer 3

the release of chemical substances to break down the food

Question 4

how is motility related to digestion?

Answer 4

it involves the muscular activity which will propulse the food and allow for chemical breakdown and mixing of foods

Question 5

what is the absorption aspect of digestion?

Answer 5

the transfer of nutrients into blood circulation

Question 6

what is the role of GIT in homeostasis?

Answer 6

o Provide nutrients to the body which is needed for basic functions, regulation, growth & repair

Question 7

what proportion of nutrients is absorbed by the GIT?

Answer 7

CHO 99%
FAT 95%
PROTEIN 92%

Question 8

what properties of the GIT were observed in earth worms?

Answer 8

o Tubular nature

o Communication with the external environment at both ends

Question 9

what is the length of the GIT in humans?

Answer 9

~4.5 m in adults

Question 10

how much bigger is the GIT from the inside than the outside?

Answer 10

600x

Question 11

what is the area covered by the GIT in adults?

Answer 11

200-250 m^2

Question 12

what is the advantage of having such a large surface area in the GIT?

Answer 12

 Great increase in area allows to obtain the ability to absorb nutrients in such an efficient way

Question 13

how is the wall of the GIT divided?

Answer 13

into 4 functional layers

Question 14

what are the layers that compose the wall of the GIT?

Answer 14

• serosa
• muscularis externa
• submucosa
• mucosa

Question 15

what layer of the GIT is identified as being “thin, but though layer of connective tissue which surround the entire tube?”

Answer 15

serosa

Question 16

what layer is o Continuous with the messenter, holds the GIT in place?

Answer 16

serosa

Question 17

what type of fibers is the musculais externa composed of?

Answer 17

longitudinal fibers (outer layer) and circular fibers (inner layer)

Question 18

what happens when the outer layer of the muscularis externa contracts?

Answer 18

GIT shortens

Question 19

what happens when the inner layer of the muscularis externa contracts?

Answer 19

lumen will narrow

Question 20

what part of the GIT is formed by striated muscles?

Answer 20

Top 1/3 of esophagus, oral cavity, pharynx and anal sphincter

Question 21

in what layer are the lymphatic and blood vessels found?

Answer 21

submucosa

Question 22

what is the mucosa layer composed of?

Answer 22

• muscularis mucosae
• lamina propria
• epithelial cells

Question 23

what is muscularis mucosae?

Answer 23

smooth muscle

Question 24

what is lamina propria?

Answer 24

loose connective tissue

Question 25

what is the function of the epithelial cells?

Answer 25

secretory ; endocrine and exocrine gland | plays a role in absorption

Question 26

does the ENS require input from the CNS?

Answer 26

NO

Question 27

What is the ENS defined as?

Answer 27

• Independent, integrative nervous system

Question 28

what is the main function of the ENS?

Answer 28

``` activities of muscular and secretory and absorptive elements of the GIT such as o Initiates o Programs o Regulates o Coordinates ```

Question 29

what are the plexuses that form the GIT?

Answer 29

submucosal and myenteric plexus

Question 30

what is a plexus?

Answer 30

collection of nerve cell bodies

Question 31

where are sensory neurons receptors located?

Answer 31

receptors in mucosal/muscle layer

Question 32

what do motor neurons in the ENS activate?

Answer 32

• Activate secretory cells, muscle cells and motor neurons (expand action of the neurons across the GIT wall)

Question 33

although the plexuses are anatomically different in the ENS, do the function as one or multiple units?

Answer 33

function as a single unit

Question 34

what does the myenteric plexus control?

Answer 34

smooth muscle

Question 35

what does the submucosal plexus control?

Answer 35

controls glands of the endocrine cells

Question 36

excitatory enteric neurons act on which receptors?

Answer 36

muscarinic receptors

Question 37

what is released by excitatory enteric neurons?

Answer 37

ACh

Question 38

inhibitory enteric neurons act on which receptors?

Answer 38

NANC (non-adrenergic/non cholinergic)

Question 39

where do the sensory fibers in the cell bodies in plexuses receive information from?

Answer 39

they receive information from the gut chemo and mechanoreceptors

Question 40

how is the stimulus transformed into a response?

Answer 40

stimulus sent to receptors then to nerve plexus then to muscle cells or gland to produce a response

Question 41

what is the length of intra mural reflex

Answer 41

short

Question 42

what do parasympathetic neurons reach the wall of the GIT as?

Answer 42

preganglionic fibers

Question 43

what do preganglionic fibers synapse via?

Answer 43

• They synapse via nicotinic ACh receptors with enteric neurons

Question 44

what does it result in the system in parasympathetic neurons

Answer 44

o Increases excitation in the system

Question 45

what do sympathetic neurons reach the wall of the GIT as?

Answer 45

postganglionic fibers

Question 46

what do postganglionic fibers synapse via?

Answer 46

• Synapses via NA receptors with enteric neurons

Question 47

what effect is exerted by sympathetic neurons?

Answer 47

inhibitory effect thus causes vasoconstriction

Question 48

what reflexes are permitted by sensory neurons?

Answer 48

long reflexes

Question 49

give examples of some Non-GIT hormones?

Answer 49

o Growth hormones, thyroid hormones

Question 50

what may non-GIT hormones influence?

Answer 50

growth and development of the GIT

Question 51

can hormones be released by the GIT but influence activities outside of it?

Answer 51

yes, ex. grehlin increases appetide at the hypothalamic feeding center

Question 52

generally what do GIT hormones regulate?

Answer 52

activities within the GIT

Question 53

how does hormonal regulation of GIT actiity function?

Answer 53

diffusion of the endocrine system

Question 54

what is the largest and most diversified endocrine system of the body

Answer 54

GIT endocrine system

Question 55

how many hormones get released by the GIT?

Answer 55

~20-30

Question 56

what is a endocrine cell that releases a hormone that functions on itself?

Answer 56

Autocrine

Question 57

what is an endocrine cell that affects neighboring cells when releasing hormones?

Answer 57

paracrine cell

Question 58

what is the endocrine effect?

Answer 58

hormones release and enter the blood stream to get to other regions

Question 59

what type of hormones are the regulatory hormones of the GIT

Answer 59

Peptide hormones

Question 60

what are regulatory hormones of the GIT released from?

Answer 60

mucosa

Question 61

what is the pathway of the regulatory hormones of the GIT when released from the mucosa?

Answer 61

blood to liver to heart, through systemic circulation through out the body until they reach target cells

Question 62

what happens when a hormone interacts in a synergistical manner with a NT?

Answer 62

they potentiate one another

Question 63

what happens when a hormone interacts in a antagonistic manner with a NT?

Answer 63

they inhibit one another

Question 64

when talking about muscular activity of the GIT, what layers are involved?

Answer 64

2 muscle layers of the muscularis externa

Question 65

when referring to propulsion through the GIT; what does segmentation refer to?

Answer 65

rings of contraction causing for closing at different locations at different times

Question 66

what is persistalsis?

Answer 66

circular muscles where the ring of the muscles moves along the wall of the GIT

Question 67

how can the flow in the GIT be characterized?

Answer 67

- slow - aboral - little to no resistance

Question 68

what is the other name given to the oral phase of swallowing?

Answer 68

volontary phase

Question 69

what is carried out by the oral phase of swallowing?

Answer 69

food is transported from anterior mouth to the pharynx

Question 70

what does swallowing involved?

Answer 70

Involves a series of reflexes coordinated in the deglutition center of the medulla oblongata via the cortex.

Question 71

where is the pharynx located?

Answer 71

back of the throat

Question 72

what senses the presence of the bolus in the pharyngeal phase?

Answer 72

sensory receptors

Question 73

in the pharyngeal phase. how does food move down?

Answer 73

-reflexes causes it to move down

Question 74

what happens when the bolus presses down on the epilottis?

Answer 74

reflexive contraction of the vocal cords and closure of the glottis and protect the lower airways

Question 75

what occurs when swallowing?

Answer 75

apnea

Question 76

what happes to the UES in the pharyngeal phase of swallowing?

Answer 76

it relaxes

Question 77

what are deglutition reflexes?

Answer 77

a series of protective reflexes is initasatied by stimulation of afferent fibers in the pharynx

Question 78

what signals the deglutition reflex?

Answer 78

the medulla

Question 79

what is controlled by the deglutition reflex?

Answer 79

o Protective functions o Relaxation UES o Deglutition apnea o Contraction of the pharyngeal muscles

Question 80

what type of muscles composes the UES?

Answer 80

striated muscle

Question 81

what innervates the UES?

Answer 81

somatic- Vagus N (X)

Question 82

how is the UES when no food is present?

Answer 82

its contracted

Question 83

what NT is released to ensure closure of the UES?

Answer 83

ACh

Question 84

what is deglutition relaxation?

Answer 84

cessation of the impulse causes the muscle to relax

Question 85

what happens to ACh in the deglutition relaxation phase

Answer 85

decreases