HISTOLOGY : GI tract 1

Question 1

what are the layers of the GIT?

Answer 1

Question 2

what forms the lining of the tract?

Answer 2

mucosa

Question 3

what are the 3 layers of mucosa?

Answer 3

1. epithelium — protective secretive and/or absorptive
2. lamina propria — connective tissue containing vessels, glands and lymphoid tissue
3. muscularis mucosa — smooth muscle (inner circular, outer longitudinal), moves the mucosa

Question 4

describe submucosa

Answer 4

• dense irregular connective tissue
• supports the mucosa and provides vascular, lymphatic and nerve supplies
• glands present in some regions
• contains the submucosal (meissener’s) plexus

Question 5

describe the muscularis externa/propria

Answer 5

• smooth muscle cells — inner circular and outer longitudinal
• responsible for GI movements (peristalsis, segmentation)
• contains the myenteric (Auerbach’s) plexus

Question 6

location of meissener’s vs Auerbach’s plexus

Answer 6

submucosal/meissener’s = submucosa

myenteric/Auerbach’s = muscularis externa

Question 7

what is serosa?

Answer 7

a serous membrane that covers those structures within the peritoneal cavity

Question 8

extraperitoneal structures are attached to surrounding structures by connective tissue fibres that form the what?

Answer 8

adventitia

Question 9

what is the outer layer?

Answer 9

serosa (peritoneum) or adventitia (extraperitoneal)

Question 10

describe the enteric nervous system

Answer 10

• submucosal and myenteric nerve plexuses
• initiates short reflexes — controls local peristalsis and glandular secretions
• responsible for long GI reflexes

Question 11

what is responsible for long GI reflexes?

Answer 11

postganglionic neurones of the ANS

Question 12

submucosal/meissener’s plexus vs myenteric plexus

Answer 12

submucosal/Meissner’s plexus = in submucosa. controls mainly GI secretion and local blood flow

myenteric plexus = between the longitudinal and circular muscle layers. controls motility

Question 13

Answer 13

Question 14

Answer 14

Question 15

what cells are present in gastric pits and glands?

Answer 15

surface lining, mucous neck, parietal, chief, neuroendocrine

Question 16

what cells produce mucus in gastric pits/glands?

Answer 16

surface lining and mucous neck cells

Question 17

what do parietal cells do?

Answer 17

secrete HCl

Question 18

what do chief cells do?

Answer 18

secrete pepsinogen

Question 19

what do neuroendocrine cells secrete?

Answer 19

hormones

Question 20

gastric glands extend through ____ right down to _____?

Answer 20

glands extend through lamina propria right down to muscularis mucosa

Question 21

what type of epithelium is in oesophagus?

Answer 21

non-keratinised stratified squamous — protection

Question 22

what does the submucosa in the oesophagus contain?

Answer 22

protective mucus glands

Question 23

describe how oesophageal muscle changes throughout its length

Answer 23

upper 1/3 = skeletal
middle 1/3 = mixed
lower 1/3 = smooth

Question 24

what are rugae?

Answer 24

• mucosal folds in the stomach
• flatten out when the stomach is full

Question 25

what do gastric pits lead to?

Answer 25

gastric glands in lamina propria

Question 26

what lies beneath the gastric glands?

Answer 26

muscularis mucosa

Question 27

what are the nuclei like in epithelial cells in the stomach pits?

Answer 27

by basement membrane

Question 28

what type of cells are the epithelial cells in the stomach?

Answer 28

simple columnar — secretive and absorbtive

Question 29

how is the stomach muscle different?

Answer 29

has an extra layer for churning inner oblique, middle circular, outer longitudinal

Question 30

what is the outer layer in stomach?

Answer 30

serosa — peritoneal

Question 31

what are modifications of the small intestine to increase SA?

Answer 31

- plicae circulares - villi - microvilli

Question 32

where are plicae circulares most prominent?

Answer 32

jejunum

Question 33

describe villi

Answer 33

> extend from plicae circulares - core of lamina propria - lacteal - blood vessels

Question 34

Answer 34

Question 35

where and what are Brunner’s glands?

Answer 35

- in submucosa of duodenum - secrete an alkaline mucosa to neutralise the chyme entering the duodenum

Question 36

epithelium in small intestine?

Answer 36

simple columnar

Question 37

where is the myenteric plexus located?

Answer 37

between the 2 layers of smooth muscle (outer longitudinal and inner circular)

Question 38

what do villi have lots of?

Answer 38

lymphocytes microvilli

Question 39

why does the ileum have not as much absoprtion?

Answer 39

fewer plicae

Question 40

what are Peyer’s patches?

Answer 40

- round aggregations of lymphoid tissue - specific to ileum - in lamina propria - push into submucosa

Question 41

describe the order from caecum to rectum

Answer 41

1. caecum 2. ascending colon 3. hepatic flexure 4. transverse colon 5. splenic flexure 6. descending colon 7. sigmoid colon 8. rectum

Question 42

what are teniae coli?

Answer 42

bands of longitudinal smooth muscle in the colon

Question 43

what are epiploic appendages?

Answer 43

- fat filled structures - suspended from outer layer of large intestine

Question 44

what parts of the colon have adventitia and which parts have a serosa?

Answer 44

- ascending and descending colon = retroperitoneal = adventitia - transverse and sigmoid = intraperitoneal = serosa

Question 45

crypts in the large intestine go down to which layer?

Answer 45

muscularis mucosa

Question 46

describe crypts

Answer 46

- tall cytoplasm - basal nuceli - simple columnar - have microvilli for h2O absorption

Question 47

Answer 47

Question 48

appendix histology?

Answer 48