overview of digestion

Question 1

what is the name given to involuntary muscle contractions ?

Answer 1

peristalsis

Question 2

what is the primary driving force of digestion ?

Answer 2

peristalsis

Question 3

where are digestive enzymes secreted from ?

Answer 3

mucosae

Question 4

what do locally produced hormones do and give some examples ?

Answer 4

affect the physiological activity of the GI tract

• gastrin
• cholecystokinin

Question 5

where does the primary absorption of nutrients occur ?

Answer 5

the small intestine

Question 6

what type of fluid secretions are largely reabsorbed ?

Answer 6

salivary

gastrointestinal

Question 7

how is undigested material eliminated ?

Answer 7

by combined activity of involuntary and voluntary muscles

Question 8

what 4 major organs does the digestive tract differentiate into ?

Answer 8

• esophagus
• stomach
• small intestine
• large intestine

Question 9

how are organs separated ?

Answer 9

by muscular valves / sphincters

Question 10

what lines the inner surface of the digestive tract ?

Answer 10

mucosal layer

Question 11

where is digestion of carbohydrates initiated and by what ?

Answer 11

in the mouth

by amylase

Question 12

where does the majority of digestion + absorption of carbs + amino acids occur ?

Answer 12

across the muscosae of the stomach + small intestine

Question 13

what does the pancreas secrete and where does it pass into ?

Answer 13

HC03

lumen of small intestine

Question 14

what does the liver secrete and what does it pass into ?

Answer 14

bile salts

lumen of small intestine

Question 15

what are the 4 layers of muscle that make up the GI tract ? (deep to superficial)

Answer 15

• mucosa
• submucosa
• muscularis
• adventitia of the serosa

Question 16

what makes up the mucosa ?

Answer 16

• epithelium
• stroma
• vascularised loose connective tissue
• immunocompetent cells (lamina propria)
• smooth muscle (muscularis mucosae)

Question 17

what is the outer layer of smooth muscle in mucosa subdivided into ?

Answer 17

• inner circular

- outer longitudinal

Question 18

what does contractions of the muscularis do ?

Answer 18

throws mucosa into folds + ridges

Question 19

what is present in the submucosa ?

Answer 19

• large blood vessels
• lymphatic vessels
• nerves (messners plexus)

Question 20

where do the nerve fibres of messners plexus go ?

Answer 20

mucosa

muscularis

Question 21

how many layers of muscle exist in the muscularis externa ? and where is an exception found ?

Answer 21

• 2 both smooth

- in upper esophagus + anal sphincter there is striated fibres

Question 22

what is the arrangement of muscle in the muscularis ?

Answer 22

inner circular layers surrounded by outer longitudinal layers
circular constricts the lumen
longitudinal constricts the digestive tube

Question 23

describe the structure of adventitia / serosa :

Answer 23

several layers of loose connective tissue
alternately collagenous + elastic
covered by layer of mesothelial cells

Question 24

where are the largest arteries found?

Answer 24

longitudinally in submucosal layers

Question 25

where are smaller branches of arteries found ?

Answer 25

in serosal layer

Question 26

how do capillaries run in the muscularis layer ?

Answer 26

parallel to muscle fibres

Question 27

describe the blood supply in the mucosa

Answer 27

arteries supply an irregular capillary plexus around glands | sends terminal branches to mucosal villi (lumen of intestine)

Question 28

what is the general pattern of capillaries ?

Answer 28

fenestrated in the intestinal + exocrine epithelium

Question 29

describe the movement of veins :

Answer 29

veins arising in the mucosa anastomose in the submucosa and pass out of intesine alongside arteries

Question 30

how do lymphatic vessels arise ?

Answer 30

as blind tubes in the mucosa | known as lacteal vessels

Question 31

what do lymphatic vessels contain ? | what do they do ?

Answer 31

contain pinocytotic vesicles | shuttle macromolecules + chyclomicrons from the interstitial space into the lymphatic circulation

Question 32

how are lymph vessels found in the submucosa ?

Answer 32

large lymphatics branch freely cross muscle layers spread into the intermuscular tissue + serosa

Question 33

what do vascular + lymphatic vessels help do ?

Answer 33

aid nutrient absorption

Question 34

what fibres are found in the gastrointestinal tract ?

Answer 34

autonomic motor | sensory

Question 35

describe the formation of nerve fibres

Answer 35

ramify throughout GI tract | form a plexus in each layer

Question 36

where does the intramural parasympathetic ganglia innervate ?

Answer 36

``` submucosal plexus (meissner) between 2 layers of muscularis externa in myenteric plexus of auerbach ```

Question 37

what does innervation of the intramural parasympathetic ganglia do ?

Answer 37

stimulates motor + secretory activity of the gut

Question 38

where do the sympathetic fibres of the GI tract terminate ?

Answer 38

in the submucosal + myenteric plexus

Question 39

what does sympathetic innervation of the GI tract cause ?

Answer 39

cause constriction of blood vessels inhibits contraction of muscularis externa constrict muscularis mucosae

Question 40

where do gut hormones influence ?

Answer 40

alimentary tract neurocrine paracrine endocrine

Question 41

where are endocrine cells distributed ?

Answer 41

``` epithelia of stomach small intestine large intestine appendix distal esophageal glands ducts of liver + pancreas ```