Functional histology of GIT Flashcards
DESCRIBE MUCOSA OF STOMACH
- CELL TYPE
- OTHER FEATURES
- 3 DISTINCT HISTOLOGICAL ZONES
1.Simple columnar epithelia
2. gastric pits Gastric glands (2/3/4) - open into gastric pits
- 3 distinct histological zones
Cardia – small area
Fundus and body
Pylorus
11 CELLS OF GASTRIC GLAND
- Surface mucous cells
- Mucous neck cells
- Parietal or oxyntic cells
- Chief cells or zymogenic cells
- Neuroendocrine cells
- Enterochromafin Cells
- Ghrelinergic cells
- G cells
- Delta cells
- Stem cells
Surface mucous cells
Secrete bicarbonate and mucous
Mucous neck cells
function
Secrete mucous
Parietal or oxyntic cells
- how to tell that it apart from other cells?
- function
- Extensive eosinophilic cytoplasm
2. Secrete HCl & intrinsic factor
Chief cells or zymogenic cells
- how to tell that it apart from other cells?
- function
- Basophilic cytoplasm due to large amt. of rER.
2. Secrets pepsinogen and lipase
Neuroendocrine cells
function
Secrete Somatostatin, serotonin, gastrin, histamine, ghrelin
Enterochromafin cells
function
secrete Serotonin
Ghrelinergic cells
- Where can it be found in the Stomach?
- Function
- fundus and pylorusSecretes 2. Ghrelin when stomach is empty
and Stimulates hypothalamus to increase hunger and increase gastric acid secretion and GI motility.
G cells
- Where can it be found in the Stomach?
- Function
- pylorus
2. Secrete gastrin which Stimulates parietal cells to secrete HCl
Delta cells
- Where can it be found in the stomach?
- Function
1.pylorus
2. Produce somatostatin which
directly acts on parietal cells to reduce HCl secretion
Fundus / Body
- Described gastric pits
- Described gastric glands
- What do the glands consist of? (3)
- Gastric pits are shallow
- Gastric glands are long.
- chief cells, parietal cells, mucous neck cells
Pylorus
- Described gastric pits
- Described gastric glands
- What do the glands consist of?
- Gastric pits are deep.
- Pyloric glands are short.
- Glands consists of mucous secreting cell and neuroendocrine cells
- what does Muscularis externa of stomach consist of?
2. What does serosa consist of?
1.Inner oblique
Middle circular
Outer longitudinal
- Serosa – lining of mesothelium
Describe cells in Gastro-oesophageal junction
Abrupt transition from stratified squamous epithelium to simple columnar glandular secretory mucosa
Describe the mucosa in the small intestine
circular folds/plicae circulares
Epithelia – simple columnar with few goblet cells
Villi – surface projection from epithelial surface
Lamina propria – with crypt of Lieberkuhn/ intestinal glands , lymphocytes , payer’s patches (ileum)
Muscularis mucosae
Describe the submucosa of the small intestines
Loose areolar tissue, plexus of blood vessels , lymphocytes
Meissner’s plexus of nerves – signals glands to secrete
Brunner’s gland – duodenum
Payer’s patches – Ileum
Describe Muscular coat Of small intestines
Outer longitudinal smooth muscles
Inner circular smooth muscles
Myenteric (Auerbach’s ) plexus of nerves – controls peristalsis
What is the outermost layer of the small Intestines?
Serosa or Adventitia
3 Modifications for absorption in Small Intestine
- Circular folds (Plicae circularis/ Valves of Kerckring)
- Villi
- Microvilli
- what are Circular folds ?
2. function
- deep permanent folds of mucosa with a core of submucosa , about 1cm tall
- force chyme to spiral through the lumen, slowing its movement and allowing time for full nutrient absorption.
what are Villi ?
what type of cells in villi?
what does the core of vili contain?
Finger-like projections of mucosa, about 1mm high
epithelial cells of villi (enterocytes) are chiefly absorptive columnar cells
core of villi contains dense capillary bed and wide lymphatic capillary called lacteal.
Microvilli function
give the mucosal surface a fuzzy appearance called brush border.
- Small intestine - cells
- Surface Absorptive cells
- Goblet cells
- Enteroendocrine cells
- Paneth cells
- Intestinal crypts Epithelial cells
- M cells
Surface Absorptive cells
Uptake digested nutrients
Goblet cells
- number of cells
- function
- number increases from duodenum to ileum
2. Secrete mucus that lubricates chyme
Enteroendocrine cells function
Secrete hormones (secretin & cholecystokinin)
Paneth cells function
Releases antimicrobial enzymes such as defesins and lysozyme
Intestinal crypts Epithelial cells
function
Secrete intestinal juice
M cells (microfold cells function
endocytosis of antigens from the lumen and transport to the underlying lymphoid tissue where immune response is initiated
Large Intestine - colon
cell type?
Simple columnar epithelium with numerous goblet cells
where does Epithelium in large intestin change?
Epithelium changes at lower part of anal canal (below pectinate line)
stratified squamous epithelium
presence of villi in large intestine
Villi are absent
glands present
what type of gland?
Intestinal crypts of Leiberkuhn –
simple tubular glands
glands present in large intestine
what type of gland?
Intestinal crypts of Leiberkuhn –
simple tubular glands
describe Submucosa in Large intestine
considerable amount of fat
Describe large intestine in Muscularis externa
inner circular
Outer longitudinal – forms 3 flattened thicker strands taenia coli
Ano-rectal junction
cell type
Columnar epithelia changes to stratified epithelia
Appendix
Mucosa
1.cell type
- Lamina propria
constituents - Muscularis mucosae
- Simple columnar epithelia
- Lamina propria
Crypts of Lieberkuhn – few compared to colon
lymphoid tissue
- interrupted
Appendix
Submucosa
lymphoid tissue
Appendix
Muscularis externa
inner circular and outer longitudinal muscles
appendix
outmost layer
Serosa
Liver
Both exocrine and endocrine gland.
Glisson’s capsule – CT covering
liver cells / Hepatocytes ( polyhedral shape).
in cords radiating from central vein .
sinusoids present in between the cell cords.
sinusoids with Von Kupffer cells ( star-shaped macrophages).
Liver sinusoids – enlarged, leaky capillaries located between hepatic plates
Kupffer cells – hepatic macrophages found in lining of sinusoids
Space of Disse (perisinusoidal space) space between the hepatocytes and sinusoids
Bile canaliculi - belt like network around individual hepatocytes
Gallbladder
Mucosa
Lamina propria
Muscular layer
Outer layer
Mucosa – surface epithelium (simple columnar with brush border) & lamina propria and is devoid of glands.
Muscular layer (Fibromuscular coat) – smooth muscle fibres interwoven with lot of collagen & elastic fibers
Outer layer
Perimuscular coat/Adventia (liver side) – connective tissue rich in elastic fibers.
Serosa (unattached side)- visceral peritoneum over the perimuscular connective tissue
Pancreas
Exocrine part
CT capsule surrounds pancreas
Septa divide it into lobules
Compound acinar gland (serous acinus)
Centro-acinar cells
cubical cells lining the junction of acinus and duct
Intercalated, intralobular and interlobular ducts
Pancreas- structure
Acinar wall lined by tall columnar secretory cells
Cells present basal and apical zones
Basal zone basophilic, striated and has mitochondria and rough endoplasmic reticulum
Nucleus is basal
Apical zone eosinophilic and has trypsinogen granules in Golgi apparatus
Secretions
1500 – 3000ml pancreatic fluid (alkaline)
Contain water, ions, lipases, proteases, amylase, nucleases, ribonuclease
Pancreas - Endocrine part
Endocrine part – accounts for 2% of pancreatic mass
Islet of Langerhans – abundant in tail region
alpha cells (glucagon) – 20%
beta cells (insulin) - 70% & centrally located
delta cells (somatostatin & pancreatic gastrin)
PP cells - pancreatic polypeptides
Esophagus
Mucosa - Stratified squamous non keratinized epithelia
for protection
Mucous oesophageal glands in LP
Submucosa
oesophageal glands - produce mucous
reduces friction between bolus and esophageal lining
Meissner’s nerve plexus
Muscularis externa
Inner circular & outer longitudinal muscles
Upper 1/3rd – striated
Middle 1/3rd – mixed
Lower 1/3rd – smooth
for peristaltic movement
Myenteric nerve plexus
Adventitia /serosa – serosa in the abdominal part
