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GI (Semester 4) > 2.2 Histology of the GI tract > Flashcards

2.2 Histology of the GI tract Flashcards

1
Q

List the 4 histological layers of the GI tract and describe what is in each

A

Mucosa: epithelia, lamina propria, muscularis mucosae (smooth muscle)

Submucosa: connective tissue, blood, lymph vessels, fat and Meissner’s nerve plexus

Muscularis Externa: inner circular and outer longituidnal layers with Auerbach’s nerve plexus located between layers

Serosa: connective tissue with mesothelial covering (adventitia on retroperitoneal regions)

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2
Q

List the functions of the following:

oesophagus, stomach, small intestine, large intetsine

A

oesophagus: transport of chewed food
stomach: secretion of acid, mucus, pepsinogen

small intestine: digestion and absorption

large intetsine: absorption of H2O and passage of bowel contents

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3
Q

List the 3 salivary glands and what each secretes

A

Sublingual: mucus

Parotid: serous

Submandibular: both

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4
Q

Which parts of the esophagus are voluntary and involuntary?

A

Upper 1/3: Voluntary (also contains skeletal muscle)
Lower 2/:3: Involuntary, purely peristalsis (smooth muscle)

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5
Q

Name the epithelia and their functions

Mouth and Oesophagus
Stomach and Intestines
Rectum

A

Mouth and Oesophagus - stratified squamous non- keratinised provides protection from abrasion and acid reflux

Stomach and Intestines - simple columnar to aid in secretion and absorption

Rectum - stratified squamous non- keratinised for protection and to resist abrasion

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6
Q

Below is a histolgical section of an oesophagus

Lable the black arrow + list 2 cell types that would also be found here

A

GALT (gut associated lymphoid tissue) (the mucosa is associated with regions of GALT).

Dendritic antigen presenting and Langerhan cells can also be found here

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7
Q

What is the lower part of the oesophagus that connects to the stomach called?

A

The gastro-oesophageal junction

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8
Q

The stomach contains an additonal layer of what?

A

Olique smooth muscle

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9
Q

Within the stomach, the mucosa and submucose are arranged into fold known as ____ the purpose of these is to _____

A

Rugae

Flatten with distention to increase volume of stomach

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10
Q

What are the four regions of the stomach

A

1) Cardia- continuous with the oesophagus
2) Fundas
3) Body
4) Pylorus- leads to duodenum

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11
Q

What are both the cardia and fundas of the stomach covered in? What is the purpose of these?

A

Covered in gastric pits that leads to gastric glands.

These secrete hydrochloric acid, mucus and digestive enzymes

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12
Q

What is the sphincter at which the stomach opens into the duodenum called?

A

Pyloric Sphincter

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13
Q

What epithelium type lines the gastric pits?

A

Simple columnar

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14
Q

Label the regions and cells on the image below and state what each cell secretes

A

Surface mucous cells: alklaine fluid containing mucin

Mucus neck cell: acid fluid containing mucin

Parietal cell: intrinsic factor (B12 absorption) and HCl

Cheif cell: pepsinogen and gastric lipase

G cells/eneteroendocrine cells: secrete gastrin into the blood

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15
Q

Lable the cell types found in the gastric glands

A
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16
Q

Stem cells of the gastric epithelium are interspersed among the _________ cells and Intestinal stem cells are found in _______.

They have a _______ proliferative rate, some cells are replaced every ____-___ days.

A

mucus neck, crypts, high, 5-7

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17
Q

In which region of the glands are common progenitor cells found

A

Isthmus/ Neck

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18
Q

In what part of the GIT are plicae circularis most abdundant

A

Jejunum

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19
Q

Brunner’s gland are compound tubular glands that secrete _________ to counteract ___________.

This protects the mucous membrane and creates the optimal _______ for enzymatic digestion.

A

alkaline mucus, acidic chyme, pH

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20
Q

In what part of the small intestine are Peyers patches and Brunner glands ABSENT

A

Jejunum

21
Q

Describe the location and characteristics of a Paneth cell

A

Located in crypts

Contain characteristic red cytoplasmic granules that produce immunoglobulins, glycoprotein and lysozyme

22
Q

Describe the location and function of enterendocrine cells (K cells)

A

Located in the duodenum and jejunum and function to produce gastric inhibitory peptide (GIP) ➞ suppresses acid secretion

23
Q

Most of the small intestine is covered with a ________, (the visceral peritoneum) comprised of a thin layer of connective tissue and a ________.

The ________ produces a lubricating fluid to allow movement within the ___________, and is continuous with the ________,(an infolding of the parietal peritoneum)

A

serous membrane, mesothelium, mesothelium, peritoneal cavity, mesentery

24
Q

Name the lymphoid follicles indicated below and in which part of the GIT these are most abundant?

What is their function?

A

Peyer’s patches

Large aggregations of lymphoid follicles (MALT) found in the ileum (esp distal region) which project into the mucosa. They are covered with a layer of epithelium + relatively few goblet cells.

They function to provide immune surveillance.

25
Q

What special cell is found in the epithelium of peyer patches within the ileum

A

Specialised M-cells

These trancytose antigens from the lumen to a reservoir of immune cells enclosed by the basal aspect of the cell.

26
Q

Decribe the function of M-Cells in the Ileum

A

M (microfold) cells form a pocket that encloses T and B lymphocytes and dendritic cells.

Transcytosed antigens are taken up by dendritic cells and presented to Th-cells.

These, in turn, activate B-lymphocytes which mature and secrete IgA molecules.

IgAs are transported into the gut to neutralise invaders.

27
Q

What is Crohns disease and which part of the GI is most commonly affected?

Crohns is commonly associated with the formation of what?

A

A disease that causes transmural inflammation that leads to deep ulceration (unknown cause)

It can affect any part of the GIT but most commonly the distil Ileum or colon

Often associated with granuloma formation

28
Q

What are the 5 regions of the large intestine?

A

Caecum, apendix, colon, rectum and anal canal

29
Q

What is the main function of the large intestine?

A

The recovery of water and electrolytes, and the formation of faeces.

30
Q

What are Taeniae coli and where are they found?

A

Three longitudinal bands formed by the outer muscular layer of the colon

31
Q

At the lower region of the colon the epithelium changes, describe this change

A

Simple columnar to stratified squamous non-keratinised at the recto-anal junction AND Serosa is replaced by adventitia

32
Q

Which nerve plexus is located in the submucosa and where is it derived from?

Lists 3 things it controls

A

Meissner’s plexus ➞ derived from the Myenteric nerve plexus

Controls:

  • Glandular secretions
  • Regulates local blood flow
  • Alters electrolyte and water transport
33
Q

What nerve plexus is located in the muscularis externa and what is it derived from?

What does it control?

A

Auerbach’s plexus (b/w circular and longitudinal muscle), which is derived from plexus of PNS nerves around SMA

Controls GI tract motility/peristalsis

34
Q

Name the 7 accessory digestive organs (TTSSGLP)

A

Teeth, tongue, gall bladder, salivary glands (parotid, submandibular, sublingual), spleen, liver and pancreas

35
Q

What is the effect of the SNS and PNS nervous innervation on salivary secretions?

A

SNS: produces thicker secretions, as well as reducing blood flow to glands.

PNS: innervation stimulates release of fluid secretions and increased blood flow.

36
Q

The tongue is comprised of ________ epithelium, bearing ________ (some of which bear taste buds).

It contains skeletal muscle, with fibres orientated in ______ planes.

_______ muscles interdigitate directly with CT of tongue.

A

Stratified squamous non- keratinised, dorsal papillae, multiple, Intrinsic

37
Q

What is the function of myoepithelial cells and where are they found?

What other cell type is found here and what is its function?

A

Found in the oral cavity surrounding acini, tubules and
small ducts. Contraction of these cells helps move saliva towards the oral cavity.

Resident plasma cells are also found in the oral cavity and produce IgA.

38
Q

Describe the structure and secretion type of the following salivary glands:

  • Submandibular
  • Sublingual
  • Parotid
A

Submandibular: mixed serous/ mucous tubule-acinar glands that secrete various enzymes, including α−amylase and lysozyme. (2/3 volume)

Sublingual: branched tubule-acinar glands producing mainly
lubricating mucus

Parotid: mainly serous branched acinar glands that secrete α-
amylase (stored as zymogen granules)

39
Q

Decribe the structure of the ENDOCRINE pancreas

A

Contains islets of Langerhans with the following cell types

β-cells produces insulin
α-cells produce glucagon
γ-cells produce somatostatin
PP cells produce pancreatic polypeptide

40
Q

Describe the stucture of the EXOCRINE pancreas

A

The exocrine pancreas releases proteases, amylases, lipases and DNAses as zymogens into the duodenum via the major duodenal papilla

41
Q

What is the main digestive function of the liver and what is the purpose of this?

A

Production of bile to emulsify fats

42
Q

How are nutrients recieved from the digestive system to liver?

A

Via the portal vein

43
Q

What supplies oxygenated blood to the liver

A

Hepatic artery

44
Q

Describe the structure of a liver lobe

A

Sinusoids arise from branches of the portal vein and hepatic
artery, bathing hepatocytes in mixed venous and arterial blood.

Sinusoids merge to form the central veins of each lobe

These join to form the hepatic veins that drain into the inferior vena cava

45
Q

Where is the bile produced by the hepatocytes stored?

How does it get there and how is it concentrated

A

Stored in the gallbladder

Arrives via the cystic duct and concentrated by recovery of water

46
Q

What hormone stimulates the contraction of the gall bladder?

How is the bile transported to the duodenum?

A

Cholecystokinin.

Bile is transferred to the duodenum via the common bile duct and the major duodenal papilla

47
Q

What stimulates CCK?

A

Cholecystokinin is stimulated by the introduction of HCl, amino acids or fatty acids in the stomach or duodenum

It is secreted from duodenal APUD cells - it then triggers contraction of the gall bladder so bile is released into the duodenum via the cystic duct

48
Q

What cell lines the ducts of the biliary tract and what are their role?

A

Cholangiocytes ➞ modify the bile

49
Q

What 2 ducts fuse to form the common bile duct?

A

The cystic duct and the common hepatic duct

GI (Semester 4) (19 decks)

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