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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
Where are Brunner’s glands located?
In the proximal duodenum deep muscularis mucosa
26
What is the function of brunners glands?
Secrete alkaline mucous material onto side and bases of the crypts to neutralise chyme
27
What are the 4 layers of the gut?
Mucosa Submucosa Muscularis externa Serosa
28
What are the 3 divisions of the mucosa?
Epithelial layer Lamina propria Muscularis mucosa
29
What is the purpose of the lamina propria?
``` Contains lots of lymphoid nodules and macrophages Produces antibodies (IgA which is resistant to proteases) - protects against bacterial/viral invasion ```
30
Describe the structure of the muscularis mucosa
Layers of smooth muscle orientated in different directions
31
What is the function of the muscularis mucosae?
Keeps epithelium in contact with gut contents. | Keeps crypt components dynamic
32
What is contained within the submucosa?
``` Dense connective tissue Blood vessels Glands Lymphoid tissue Meissner’s plexus ```
33
Describe the structure of the muscularis externa
Inner circular muscle Outer longitudinal muscle Myenteric plexus between these two layers.
34
What is the landmark between the abdominal cavity and the pelvic cavity?
Pelvic brim
35
What is the function of enteroendocrine cells?
secrete hormones that control the function of the gut - secretin - cholecystokinin - gastrin
36
give 3 examples of glandular tissue of the gut
salivary glands pancreas brunners glands
37
what is the purpose of the epithelium of the gut
``` secrete mucus promote nutrient absorption selectively permeable barrier facilitate transport and digestion of food produce hormones ```
38
describe the structure of the serosa
consists of blood and lymphoid vessels adipose tissue continuous with the mesenteries
39
Describe the structure of the peritoneal cavity
double membrane secreting serous fluid into the peritoneal cavity. Consists of flattened squamous epithelium with a basement membrane and dense irregular connective tissue.
40
what is the function of mesenteries?
aids structure of abdominal viscera, holding them in place and reducing risk of torsion. secretes serous fluid, reducing friction between the abdominal viscera
41
what are intraperitoneal viscera?
organs enveloped by the peritoneum. Stomach, liver, spleen
42
what are retroperitoneal viscera? Name them
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
what is a mesentery
a double fold of peritoneum that attaches intraperitoneal structures to the posterior abdominal wall
44
which viscera have mesenteries
``` jejunum ileum appendix transverse colon sigmoid colon rectum ```
45
what is the function of a mesentery?
allows passage and transport of vessels to intraperitoneal structures from the retroperitoneal space
46
what is a peritoneal ligament
similar to a mesentery but connects two intraperitoneal viscera
47
what name is given to the midline down the abdomen
linea alba
48
what structures make up the abdominal wall
``` skin superficial fascia deep fascia exernal oblique internal oblique transverse abdominis rectus abdominis ```
49
what is the origin and insertion of transversus abdominis?
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
what is the function of the transversus abdominis?
fibres run in a transverse direction. acts to compress abdominal viscera, important for core stability.
51
what is the origin and insertion of internal oblique
Originates from the inguinal ligament, iliac crest and lumbodorsal fascia, and inserts into ribs 10-12.
52
what is the origin and insertion of external oblique
Originates from ribs 5-12, and inserts into the iliac crest and pubic tubercle.
53
what is the origin and insertion of rectus abdominis
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
what is the function of the internal oblique
Fibres run superomedially | Functions: Bilateral contraction compresses the abdomen, while unilateral contraction ipsilaterally rotates the torso.
55
what is the function of the external oblique
Fibres run superolaterally | Functions: Contralateral rotation of the torso.
56
what is the function of the rectus abdominus
compresses the abdominal viscera, stabilises the pelvis during walking, and depresses the ribs.
57
what forms the inguinal ligament?
the aponeurosis of the external oblique
58
what is the nerve supply to the anterolateral muscles?
T6 to T12 | IO and TA also supplied by L1
59
describe the structure of the rectus abdominis
paired muscle, found either side of the midline in the abdominal wall. It is split into two by the linea alba
60
what is the rectus sheath?
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
where is the arcuate line?
half way between the umbilicus and the pubic symphysis
62
what happens below the arcuate line?
all the aponeurosis from the anterolateral muscles go anterior to the rectus abdominis
63
Below the arcuate line, what separates the rectus abdominus from the abdominal contents?
Transversalis fascia | Parietal peritoneum

GI Unit (14 decks)

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