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GI Unit > 1.2 Epithelia And Layers Of The Gut > Flashcards

1.2 Epithelia And Layers Of The Gut Flashcards

1
Q

What type of epithelia lines the oesophagus and distal anus?

A

Stratified squamous

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2
Q

Why is the epithelia of the oesophagus and anus not keratinised?

A

As epithelium secretes mucus and keratinisation would stop fluid loss and secretions.

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3
Q

What is the structure of the epithelium of the mid gut?

A

Simple columnar

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4
Q

What is the main cell of the stomach?

A

Surface mucus cells. Are simple columnar cells that produce mucus and secrete via exocytosis

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5
Q

What are gastric pits?

A

Indentations in the stomach lining marking the entrance to tubular gastric glands

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6
Q

Where are neck mucus cells found?

A

At the base of the gastric pits

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7
Q

How are neck mucus cells different from surface mucus cells?

A

Smaller
More irregular
Smaller mucin vacuoles

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8
Q

Where are gastric glands located?

A

At the bottom of the gastric pits, within the lamina propria of the stomach.

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9
Q

What adaptations does the epithelium of the small intestine have to increase SA?

A
  1. Permanent folds - plicae circularis
  2. Villi - finger projections of epithelium
  3. Microvilli on enterocyte apical surface.
  4. Invagination of lumen into gut wall -crypts (s + l intestine)
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10
Q

What is the function of an enterocyte cell?

A

Absorb molecules from the gut lumen

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11
Q

What is the predominant cell of the small intestine and colon?

A

Enterocyte

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12
Q

What features of an enterocyte improve its ability to absorb molecules?

A

One cell thick
Blood vessels/lymphatics lie immediately below enterocyte in the lamina propria
Microvilli on apical membrane

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13
Q

Where are goblet cells found?

A

Along GI tract, increasing in number from the duodenum to the colon. Scattered between enterocytes.

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14
Q

What is the function of goblet cells?

A

To secrete mucus that protects and nourishes the microbiome

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15
Q

What is the function of mucus in the GI tract?

A

Acts as lubrication
Protects epithelia from chemical damage of acidic lumen contents
Forms innate physical barrier to protect against bacteria

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16
Q

What is the function of gastric surface mucus cells?

A

To secrete mucus/ HCO3- to form a barrier to stomach acid.

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17
Q

Why is it necessary to have villi in the small intestine?

A

To increase SA for absorption.

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18
Q

What specialised cells are found in the crypts of Lieberkuhn?

A

Stem cells
Paneth cells
Enteroendocrine cells.

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19
Q

Why are stem cells present in the crypts within the small and large intestine?

A

As constantly divide to replace the epithelia of the intestines every 2 to 4 days. Important to maintain barrier and protect from lumen contents.

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20
Q

What is the function of Paneth cells?

A

To secrete antibacterial proteins to protect the stem cells.

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21
Q

Where are enteroendocrine cells predominantly located?

A

Deep in the crypts and gastric glands

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22
Q

After absorption, where do the breakdown products of digestion go?

A

Lipids taken up into lymph capillaries

Amino acids and monosaccharides taken up into blood

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23
Q

Where do vessels lie in the gut wall?

A

Submucosa

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24
Q

What adaptions are there to the colon epithelia to increase water absorption?

A

Prominent lateral intracellular spaces

Many Na+/K+ ATPases on the lateral membrane

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25
Q

Where are Brunner’s glands located?

A

In the proximal duodenum deep muscularis mucosa

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26
Q

What is the function of brunners glands?

A

Secrete alkaline mucous material onto side and bases of the crypts to neutralise chyme

27
Q

What are the 4 layers of the gut?

A

Mucosa
Submucosa
Muscularis externa
Serosa

28
Q

What are the 3 divisions of the mucosa?

A

Epithelial layer
Lamina propria
Muscularis mucosa

29
Q

What is the purpose of the lamina propria?

A 
Contains lots of lymphoid nodules and macrophages 
Produces antibodies (IgA which is resistant to proteases) - protects against bacterial/viral invasion
30
Q

Describe the structure of the muscularis mucosa

A

Layers of smooth muscle orientated in different directions

31
Q

What is the function of the muscularis mucosae?

A

Keeps epithelium in contact with gut contents.

Keeps crypt components dynamic

32
Q

What is contained within the submucosa?

A 
Dense connective tissue
Blood vessels
Glands
Lymphoid tissue 
Meissner’s plexus
33
Q

Describe the structure of the muscularis externa

A

Inner circular muscle
Outer longitudinal muscle
Myenteric plexus between these two layers.

34
Q

What is the landmark between the abdominal cavity and the pelvic cavity?

A

Pelvic brim

35
Q

What is the function of enteroendocrine cells?

A

secrete hormones that control the function of the gut

  • secretin
  • cholecystokinin
  • gastrin
36
Q

give 3 examples of glandular tissue of the gut

A

salivary glands
pancreas
brunners glands

37
Q

what is the purpose of the epithelium of the gut

A 
secrete mucus
promote nutrient absorption
selectively permeable barrier
facilitate transport and digestion of food
produce hormones
38
Q

describe the structure of the serosa

A

consists of blood and lymphoid vessels
adipose tissue
continuous with the mesenteries

39
Q

Describe the structure of the peritoneal cavity

A

double membrane secreting serous fluid into the peritoneal cavity. Consists of flattened squamous epithelium with a basement membrane and dense irregular connective tissue.

40
Q

what is the function of mesenteries?

A

aids structure of abdominal viscera, holding them in place and reducing risk of torsion.
secretes serous fluid, reducing friction between the abdominal viscera

41
Q

what are intraperitoneal viscera?

A

organs enveloped by the peritoneum. Stomach, liver, spleen

42
Q

what are retroperitoneal viscera? Name them

A

organs that lie posterior to the peritoneum.
S = Suprarenal (adrenal) Glands
A = Aorta/IVC
D =Duodenum (except the proximal 2cm, the duodenal cap)
P = Pancreas (except the tail)
U = Ureters
C = Colon (ascending and descending parts)
K = Kidneys
E = (O)esophagus
R = Rectum

43
Q

what is a mesentery

A

a double fold of peritoneum that attaches intraperitoneal structures to the posterior abdominal wall

44
Q

which viscera have mesenteries

A 
jejunum
ileum
appendix
transverse colon
sigmoid colon
rectum
45
Q

what is the function of a mesentery?

A

allows passage and transport of vessels to intraperitoneal structures from the retroperitoneal space

46
Q

what is a peritoneal ligament

A

similar to a mesentery but connects two intraperitoneal viscera

47
Q

what name is given to the midline down the abdomen

A

linea alba

48
Q

what structures make up the abdominal wall

A 
skin
superficial fascia
deep fascia
exernal oblique
internal oblique
transverse abdominis
rectus abdominis
49
Q

what is the origin and insertion of transversus abdominis?

A

Originates from the inguinal ligament, costal cartilages 7-12, the iliac crest and thoracolumbar fascia. Inserts into the conjoint tendon, xiphoid process, linea alba and the pubic crest.

50
Q

what is the function of the transversus abdominis?

A

fibres run in a transverse direction. acts to compress abdominal viscera, important for core stability.

51
Q

what is the origin and insertion of internal oblique

A

Originates from the inguinal ligament, iliac crest and lumbodorsal fascia, and inserts into ribs 10-12.

52
Q

what is the origin and insertion of external oblique

A

Originates from ribs 5-12, and inserts into the iliac crest and pubic tubercle.

53
Q

what is the origin and insertion of rectus abdominis

A

Originates from the crest of the pubis, before inserting into the xiphoid process of the sternum and the costal cartilage of ribs 5-7.

54
Q

what is the function of the internal oblique

A

Fibres run superomedially

Functions: Bilateral contraction compresses the abdomen, while unilateral contraction ipsilaterally rotates the torso.

55
Q

what is the function of the external oblique

A

Fibres run superolaterally

Functions: Contralateral rotation of the torso.

56
Q

what is the function of the rectus abdominus

A

compresses the abdominal viscera, stabilises the pelvis during walking, and depresses the ribs.

57
Q

what forms the inguinal ligament?

A

the aponeurosis of the external oblique

58
Q

what is the nerve supply to the anterolateral muscles?

A

T6 to T12

IO and TA also supplied by L1

59
Q

describe the structure of the rectus abdominis

A

paired muscle, found either side of the midline in the abdominal wall. It is split into two by the linea alba

60
Q

what is the rectus sheath?

A

where the aponeurosis of the anterolateral muscles envelop the rectus abdominis. EO and IO above, IO and TA below. only exists above the arcuate line

61
Q

where is the arcuate line?

A

half way between the umbilicus and the pubic symphysis

62
Q

what happens below the arcuate line?

A

all the aponeurosis from the anterolateral muscles go anterior to the rectus abdominis

63
Q

Below the arcuate line, what separates the rectus abdominus from the abdominal contents?

A

Transversalis fascia

Parietal peritoneum

GI Unit (14 decks)

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