Anatomy Of The Intestines Flashcards by Elizabeth Stevens

What happens when the cells of the small intestine epithelium reproduce and where do they do it?

Reproduce in the villi
Migrate towards the tips, maturing as they go
-acquire capacity to absorb

How well did you know this?

Not at all

Perfectly

Microscopic structure of the small intestine?

Mucosa folded into villi

Villi separated by crypts

How well did you know this?

Not at all

Perfectly

What do the microvilli do?

Massively increase the surface area to form a brush border

How well did you know this?

Not at all

Perfectly

What does the brush border form?

An unstirred layer where nutrients meet and react with enzymes secreted by enterocytes (epithelial cells), completing digestion prior to absorption.

How well did you know this?

Not at all

Perfectly

What are the main layers of the small intestine?

Mucosa

epithelium
lamina propria
muscularis mucosae

Submucosa

connective tissue
with blood vessels, lymphatics and submucosal plexus

Muscularis externae

2 smooth muscle layers, longitudinal and circular.
Myenteric plexus lies between them

Adventitia

loosely arranged fibroblasts
collagen
vessels and nerves pass through it

Covered by mesothelium, commonly called serosa

How well did you know this?

Not at all

Perfectly

What are enterocytes?

Columnar cells which contain brush border enzymes for digestion

How well did you know this?

Not at all

Perfectly

What are goblet cells?

Exocrine glands which secrete mucin

How well did you know this?

Not at all

Perfectly

What cells do the crypts of Lieberkuhn contain?

Stem cells - produce new cells
Enteroendocrine cells - synthesise and secrete hormones
Paneth cells - secrete protective agents
Peyer’s patches (only in ileum)
Brunner’s glands - secrete alkaline fluid to neutralise chyme

How well did you know this?

Not at all

Perfectly

What protective agents do Paneth cells secrete?

Defensins and lysosyme

How well did you know this?

Not at all

Perfectly

What do Peyer’s patches do?

Contain MALT which house white blood cells and lymphocytes

Produce antibodies to protect from infection

How well did you know this?

Not at all

Perfectly

Over all function of the large intestine?

Receives digested food from small intestine, from which it absorbs water and sodium to form faeces

How well did you know this?

Not at all

Perfectly

Tell me about the cecum

First part of the colon
Blind ended sac
Slightly inferior to ileocecal junction
Can be palpated in right iliac fossa if enlarged due to poo/gas

How well did you know this?

Not at all

Perfectly

Where is the appendix?

Attached to the posteriomedial end of caecum

Contains lymphoid tissue

How well did you know this?

Not at all

Perfectly

What is the blood supply to the cecum?

Arterial: SMA -> ileocolic artery
Venous: ileocolic vein -> IMA

How well did you know this?

Not at all

Perfectly

Where does the ascending colon extend from and to?

Cecum to right lobe of liver

Right colic flexure/hepatic flexure

How well did you know this?

Not at all

Perfectly

Where does the transverse colon extend from and to?

Right colic flexure -> left colic flexure/splenic flexure

How well did you know this?

Not at all

Perfectly

Where does the descending colon extend from and to?

Left colic flexure to the sigmoid colon

How well did you know this?

Not at all

Perfectly

Where in relation to the left kidney is the descending colon?

Passes anteriorly to it over its lateral border

How well did you know this?

Not at all

Perfectly

What marks the beginning of the sigmoid colon?

Where the descending colon turns medially

How well did you know this?

Not at all

Perfectly

What structures are just posterior to the sigmoid colon?

Left ureter

Left common iliac artery

How well did you know this?

Not at all

Perfectly

What is lateral to the ascending and descending colon? Function?

Left and right paracolic gutters

Drain any fluid that leaks from the colon

How well did you know this?

Not at all

Perfectly

Clinical relevance of the paracolic gutters?

Allow any potentially infectious material to circulate around the peritoneal cavity which can cause further infection
This is how a ruptured appendix can cause peritonitis

How well did you know this?

Not at all

Perfectly

Arterial and venous supplies to the ascending colon?

Arterial - ileocolic and right colic branches of SMA

Venous - ileocolic and right colic tributaries of SMV

How well did you know this?

Not at all

Perfectly

Blood supply of the transverse colon?

Arterial - middle colic of SMA

Venous - SMV

How well did you know this?

Not at all

Perfectly

Blood supply of descending colon?

Arterial: Left colic and superior sigmoid - branches of IMA | Venous - IMV

Blood supply of sigmoidal colon?

Arterial: sigmoid arteries - branches of IMA Venous: IMV

Which artery forms an anastamosis between the superior and inferior mesenteric arteries?

Marginal artery

Clinical relevance of the colonic blood supply?

It is collateral, so maintains blood supply in case of occlusion/stenosis of one of the major arteries.

Where is the rectus located?

Begins at S3 Retroperitoneal Immediately anterior to sacrum

How does the extension of the peritoneal cavity in the pelvis differ between men and women?

Women: formed between posterior wall of uterus and colon - recto-uterine pouch / pouch of Douglas Men: between posterior wall of bladder and the colon - retro-vesicle pouch

What can an ulcer in the duodenal cap/ampulla erode into?

Gastroduodenal artery, causing massive blood loss

What sections is the duodenum divided into? At which vertebral level is each?

Superior - L1 Descending - L1-L3 Inferior - L3 Ascending - L3-2

Which part of the duodenum is connected to the liver and by what?

Superior | Hepatoduodenal ligament

What are the first 2cm of the duodenum called?

The duodenal cap or ampulla

Which part of the duodenum curves around the head of the pancreas?

Descending

What structures does the inferior portion of the duodenum cross over?

Aorta and IVC | Posterior to SMA and SMV

Which part of the duodenum is most susceptible to duodenal ulcers?

Superior part

Where does the duodenum join the jejunum and what happens here?

Duodenojunal flexure | Suspensory muscle of the duodenum contracts which can widen the flexure

What does the ileocecal valve do?

Prevents reflux of contents back into the ileum

Features of the jejunum?

``` Mainly in upper left quadrant Thick intestinal wall Longer vasa recta than ileum Fewer arcades Red in colour ```

What are arcades?

Arterial loops

What is between the layers of the mesentery of the small intestine?

Superior mesenteric vessels Lymph nodes Fat Autonomic nerves

Features of the ileum?

``` Mainly in lower right quadrant Thin intestinal wall Shorter vasa recta More arcades Pink in colour ```

Arterial blood supply to the small intestine?

Before the duodenal papilla -gastroduodenal artery - branch of the celiac trunk Distal to duodenal papilla -inferior pancreaticoduodenal artery, branch of SMA

What do the veins of the small intestine drain into?

Hepatic portal vein | they follow the major arteries

At what level does the SMA arise from the abdominal aorta?

Blood supply of the jejunum and the ileum?

Jejunal and ileal arteries which are branches of the SMA | Split into many branches and form arcades, vasa recta arise from them

Venous drainage of the jejunum and ileum?

Superior mesenteric vein

Which two veins anastamose and where to form the hepatic portal vein?

Superior mesenteric vein and splenic vein | At the neck of the pancreas

Which parts of the duodenum are retroperitoneal and intraperitoneal?

First segment is intra-peritoneal | Rest is secondarily peritoneal so jejunum and ileum are mobile

Which has lumen is larger in diameter, small or large intestine?

Large has a larger diameter

What lymphoid tissue the small and large intestines have?

Small - Peyer's patches | Large - none

What is the appendix? How long is it?

A blind intestinal diverticulum | 6-10cm long

Blood supply to the appendix?

Arterial: Abdominal aorta -> ileocolic -> appendicular Venous Ileocolic -> SMV

Arterial supply of the rectum?

Proximal rectum IMA -> superior rectal -> right and left branches Distal Common iliac -> R and L internal iliac -right and left middle rectal -inferior pudendal -> right and left inferior rectal

Venous drainage of the rectum?

Superior rectal vein -> IMV -> splenic -> portal | Middle and inferior rectal veins -> systemic system

How do you know where the anal canal begins?

Where the rental ampulla narrows at the level of U-shaped sling formed by the puborectalis muscle

How does the anal canal descend?

Posterioinferiorly | Between anococcygeal ligament and perineal body

What is the superior half of the mucous membrane of the anus characterised by?

Mucous membranes

Describe the anal columns

In the superior half of mucous membranes Contain terminal branches of superior rectal artery and vein Inferior ends are joined by anal valves Superior to valves are anal sinuses

What does passing faeces compressed when passing through the anal canal and what is the point?

Anal sinuses Exude mucus Aids in evacuation of faeces

What forms the pectinate line?

Inferior comb-like shape of anal valves

Vasculature of the anal canal above the pectinate line?

IMA -> superior rectal

Arterial supply of the anal canal below the pectinate line?

Inferior rectal arteries and middle rectal arteries | Middle anastomose with superior and inferior arteries

What is the inferior part of the anal canal derived from?

Endoderm

Innervation of the anal canal?

Above pectinate line - visceral - visceral afferents travel with the parasympathetic nervous system to spinal sensory ganglia S2-S4 (referred pain) Below pectinate line - somatic - inferior anal nerves - branches of pudendal nerve

What sensation is the anus sensitive to?

Above p line -stretching ``` Below p line -pain -touch -temperature Well localised ```