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GIT pathology > Histology of GIT > Flashcards

Histology of GIT Flashcards

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1
Q

Lisst the four layers

A
  • Mucosa
  • Submucosa
  • Muscularis propria
  • Adventitia/Serosa

  • Mucosal changes due to different functions of the various organs e.g. submucosa thickness varies
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2
Q

Describe the components of the mucosa

A

◼ epithelium
◼ lamina propria
◼ muscularis mucosae

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3
Q

Describe the contents of the submucosa

A

loose collagenous
tissue containing
blood vessels,
lymphatics, nerve
submucosal plexuses
(meissner’s) and
lymphoid aggregates

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4
Q

Describe the muscularis propria

A

generally two layers
of smooth muscle
(inner circular and
outer longitudinal) to
allow for peristalsis,
and nerve plexuses
(myenteric)

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5
Q

Describe the adventitia and serosa

A

Adventitia
loose supporting
tissue containing
blood vessels and
nerves

Serosa
Mesothelial lining
covering the outer
most aspect of
gastrointestinal
tract

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6
Q

Distinguish between adventitia and serosa

A

Adventitia – found all parts
of GIT, lies between
muscularis propria and
serosa (in some parts of
bowel minimal to non-
existent)

Serosa – outer most lining
of those parts of GIT found
within abdomen (similar to
pleura of lungs)
- intraperitoneal?

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7
Q

List the functions of GIT mucosa

A
  • Protection - barrier to external environment
  • Secretion - and synthesis of various substances
    (e.g digestive enzymes, mucus, antibodies,
    hormones)
  • Absorption - products of digestion, water,
    electrolytes
  • Immunological functions - containing lymphoid tissue
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8
Q

Describe the histology of the oesophagus

A
  • Lumen is lined by
    protective stratified
    squamous epithelium
  • Primary function is to
    transfer ingested food
    and fluids from mouth
    to stomach
  • Thin lamina propria
    contains lymphoid
    tissue –> immune role
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9
Q

Describe the oesophageal submucosa

A
  • Submucosa contains
  • elastic fibres (to
    allow distension by a
    bolus of food)
  • mucous glands (to
    aid in lubrication of
    bolus)
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10
Q

Describe Barrett’s

A
  • Barrett’s oesophagus / adenocarcinoma
  • metaplasia (Squamous to glandular epithelium), goblet cells
  • biggest RF is untreated chronic reflux
  • can become dysplastic i.e. malignant potential, cytological features of malignancy, +/- BM invasion
  • if resected – big section, implications for morbidity
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11
Q

Describe the gasto-oesophageal junction

A

stratified
squamous
epithelium
of
oesophagus
columnar
epithelium
of stomach

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12
Q

Describe the functions of the stomach

A

◼ Holds food it receives – Distensible
◼ Responsible for mechanical breakdown of
food - muscular strength (churning
movements)
◼ Produces various substances which make up
gastric juice - responsible for partial chemical
digestion of food

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13
Q

Describe the stomach mucosa

A
  • Cardia: small area
    around oesophageal
    orifice, mainly mucus
    secreting glands, some
    neuroendocrine cells
  • Fundus/body: largest
    part, different cells
    secrete gastric acid,
    mucus and hormones
  • Pylorus: small area at
    base of stomach,
    mucus secreting cells,
    neuroendocrine cells
    (secrete gastrin)
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14
Q

List the cell types foundin the stomach mucosa

A
  • Fundus and body consist of
    straight tubular glands
    (formed by simple columnar
    epithelium)
    • note surface cells are low columnar or cuboidal
  • Contains large mucinogen
    granules which maintain the
    thick mucus sheet protecting
    epithelium
  • Surface mucous cells
    secrete bicarbonate, helps to
    protect epithelium from
    acidic gastric juices
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15
Q

List and describe the cell types of the gastric glands

A
  • Parietal cells: secrete
    gastric acid and
    intrinsic factor
    (needed to absorb
    vitamin B12 in
    terminal ileum), stain
    pink (many
    mitochondria)
  • Chief cells: secrete
    pepsin, stain blue
    (many ribosomes)
    http://www.lab.anhb.uwa.edu.au/mb140/default.htm

Gastric glands – cell types
* Neuroendocrine cells
– secrete hormones
such as serotonin and
gastrin
* Stem cells – can
differentiate into any
of other cells as
required —> constant turnover of cells

Found in antrum

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16
Q

summarise the layers ofhte stimamch

A
  • Lamina propria – very thin
  • Submucosa – contains nerves and
    ganglion cells which make up submucosal
    plexus
  • Muscularis propria – distinguished in
    stomach by addition of a third muscular
    layer, inner oblique layer
17
Q

**Why understand histology of
stomach?

A

**
* Gastritis – H. pylori
Gastric ulcer
H. Pylori organisms
- tend to hang out in crypts or in mucin on antral surface
- ulcer —> adenocarcinoma and lymphoma risk

18
Q

Describe the gasto-duodenal junction

A

Cell types are the same but the structure of the epithelium changes.

Simple
columnar
epithelium
of stomach

vs

villous
mucosa
lined by
columnar
mucosa with
goblet cells
of duodenum

19
Q

Broadly describe the anatomy and function of small intestine, and hwo the histology facilitates this

A
  • Three anatomic components:
    duodenum, jejunum and ileum
  • Main functions:
  • digest food
  • absorb the products of digestion
  • Specialised cells increase surface area (plicae
    circulares, villi, and microvilli) to enhance absorption
  • Velvety, undulating appearance
20
Q

Describe SI mucosa

A
  • Villi- finger-like
    projections of mucosa
  • increase surface
    area for absorption
  • longest in
    duodenum, shorter
    towards ileum
  • Crypts of Lieberkuhn -
    between villi
  • Peyer’s patches -
    lymphatic tissue within
    lamina propria (in ileum)
21
Q

Describe the epithelium of the small intestine

A
  • Simple columnar
    epithelium aka Enterocytes:
    absorptive cells with
    microvilli, cover villi
    and crypts
  • Goblet cells:
    scattered along
    epithelium and
    produce mucus
  • Paneth cells: base of crypts,
    contain secretory granules of
    lysozymes, can phagocytose
    some bacteria and protozoa
  • Neuroendocrine cells:
    produce hormones such as
    secretin (important for
    digestion- regulates pH)
  • Stem cells: at base of crypts – regeneration and high cell turnover
  • Intraepithelial lymphocytes:
    mainly T cells
22
Q

What are the features of duodenal submucosa

A

submucosal mucus
producing glands,
Brunner’s glands
lymphoid tissue

23
Q

Describe histology of Crohn’s

A

**
* Crohn’s disease – transmural inflammation
- occurs along length of GIT
- characterised by loss of villi in addition to transmural inflammation
- macro: fissuring ulcers, pseudoulcers

24
Q

Describe the ileo-caecal junction

A

lined by
columnar
mucosa with
goblet cells and
Paneth cells of
ileum

vs

Mucosa with
crypts lined by
columnar mucosa
with goblet cells
of large intestine

25
Q

Overview: anatomy and function large intestine

A
  • Anatomical components:
    Caecum, appendix, ascending colon,
    transverse colon, descending colon, sigmoid
    colon and rectum
  • Main functions:
  • absorb water and electrolytes from bowel
    contents
  • to move contents distally for elimination
  • Smooth lumen (no plicae circulares
    or villi) – dd. Haustra- caused by
    taenia coli
26
Q

Describe the mucosa of the large intestine

A
  • Simple columnar
    epithelium which forms
    tubular glands (crypts)
  • Enterocyte, - absorptive
    cell - microvilli (most
    common cell type)
  • Goblet cells produce
    mucus, needed to
    lubricate intestine and
    allow for passage of
    bowel contents
  • Stem cells found at base
    of crypts
27
Q

What is a key differentiator between small and large intestine?

A

finger-like villi and crypts vs
deep crypts without villi

28
Q

List macro and micro features of the large intestine

A
  • Teniae coli -

longitudinal bands,
seen macroscopically
are formed by outer
longitudinal layer of
muscularis propria
* Thick muscularis propria
seen microscopically

Also seen microscopically:
lymphoid tissue,
deep crypts with goblet
cells and enterocytes

29
Q

Describe the appendix

A

*Appendix arises from the
caecum and is lined by large
intestine mucosa
* Abundant lymphoid tissue
in lamina propria and
submucosa

30
Q

**Why understand histology of large
intestine?

A

**
* Colorectal cancer - staging
- need to know layers of colon to know extent of invasion
- T4 tends to be unresectable

31
Q

Describe the recto-anal junction

A

glandular mucosa of rectum

vs

stratified
squamous
epithelium
of anus

  • a gradual transition zone
32
Q

Describe anatomy and function of anus

A
  • Main functions:
  • Protection (squamous
    mucosa through to skin
    containing sebaceous
    glands and apocrine
    sweat glands) - some lubrication
  • Outlet for passage of
    faeces
33
Q

**Why understand histology of the
anus?

A

**
* Squamous carcinoma, linked to HPV, high morbidity

GIT pathology (3 decks)

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