Gross Anatomy and Functional Histology of the Large Intestine Flashcards
What are the structures derived from the foregut? (5)
- Respiratory tress from larynx to alveoli
- Esophagus
- Stomach
- Liver, gallbladder and pancreas
- Duodenum as far as the entrance of the common bile duct
What is the main blood supply of the foregut?
Celiac trunk at T12
What are the nerve innervations of the foregut?
Greater splanchnic and vagal nerve
What are the structures deruved from the midgut? (5)
- Duodenum distal to the opening of the common bile duct
- Jejunum and ileum
- Cecum and appendix
- Ascending colon
- Proximal part of transverse colon
What is the blood supply to the midgut?
Superior mesentery artery at L1
What is the nerve innervation of the midgut?
Lesser thoracic splanchnic and vagal nerve
What are the structures derived from the hindgut? (4)
- Distal part of the transverse colon
- Descending colon
- Sigmoid colon
- Rectum and upper part of anal canal
Where is the lower part of the anal canal derived from?
Ectoderm
What is the parasympathetic nerve innervation of the hindgut?
Pelvic splanchnic nerves (S2 - 4)
What kind of nerves innervate the lower part of the GIT?
Sacral nerves, not cranial
What is the blood supply to the hindgut?
Inferior mesenteric artery at L3
What is the sympathetic innervation of the hindgut?
Lumbar splanchnic nerves
What is the cloaca separated into?
Urogenita sinus
Rectonanal sinus
What does the urogenital sinus contribute in?
Formation of the urinary bladder and the urethra
What does the rectoanal canal contribute in?
Formation of the rectum and upper part of the anal canal
What is the allantoid?
Connection between the urinary bladder and the yolk sac
Which other structure is the allantoid similar to?
Viteline duct
What does the tip of the urorectal septum divide into?
Urogenital membrane
Anal membrane
Up until does the urorectal septum grow?
Until it reaches the ectoderm
What is the function of the urorectal septum?
Separates the cloaca and the hindgut into anterior and posterior systems (membranes)
What is the perineal body a part of?
Part of the tip of the urorectal septum
What does the anal membrane cover?
Anorectal canal
What happens to both the urogenital and anal membranes?
They both degenerate so that the two systems can open into the exterior
Which pathology occurs if the urogenital and anal membranes do not degenerate?
Imperforate anus
What are the types of imperforate anus?
Anal atresia
Anal stenosis
What is an imperforate anus?
A defect in which the opening to the anus is either missing or blocked
What causes the imperforate anus to occur?
Anal membrane fails to breakdown
Deviation in the path of the growth of the urorectal septum
What are the main functions of the large intestine?
Reabsorption of H2O and salts
Absorption of vitamins
Storage of feces
Which of the structures of the large intestine are intraperitoneal or attached to a mesentery?
Cecum (no specific mesentery but still has motility)
Appendix
Transverse colon
Sigmoid colon
Upper 1/3 of rectum
Which of the structures of the large intestine are retroperitoneal or have no mesentery attached to them?
Ascending colon
Descending colon
Middle 1/3 of the rectum
What kind of structure is the lower 1/3 of the rectum?
Infraperitoneal
What happens if the appendix gets obstructed or inflammed?
Appendecitis
What are taeniae coli?
Bands of muscle of the large intestine, form a layer around the appendix
Which artery is specific to the appendix?
Appendicular artery
Where is appendicular artery derived from?
The posterior cecal artery
Why is it important to know the location of the appendicular artery?
In the case of appendectomy, this artery has to be ligated
What is the location of the orifice of the appendix in regard to the ileocecal sphincter?
The office of the appendix is inferior to the ileocecal sphincter
What are the nerve supplies of the appendix?
Autonomic nerve fibers and afferent nerve fibers
Where is the initial pain of appendicitis?
Initial pain would be at the umbilicus area. Afterward, it migrates to the right lower quadrant at the site of the appendix
What is the most common location of the appendix?
Retrocecal location, the appendix is just behind the cecum
What are the other possible locations of the appendix? Describe them
Pelvic (32%) (Just behind the pelvis)
Paracecal (On the side of the cecum)
Subcecal (Under the cecum)
Preileal (Anterior to the ileum)
Postileal (Posterior to the ileum)
How does the pain relate to the location of the appendix?
With appendicitis, based on the location of the appendix, the pain will be different
What are the characteristics of the large intestine?
Hasutrae
Appendices epiploicae
Taenia coli
What are the divisions of the colon?
Ascending
Transverse
Descending
Sigmoid
What causes the haustrae in the large intestine?
Sacculations
Where does the large intestine end?
At the anus
What are the sphincters of the anus?
Internal anal
External anal
Which is the voluntary and which is the involuntary anal sphincter?
Internal sphincter –> Involuntary
External sphincter –> Voluntary
What is the muscle of the internal anal sphincter?
Smooth muscle
Which anal sphincter is made up of skeletal muscle?
External anal sphincter
What are the branches of the superior mesenteric artery that are related to the large intestine?
Ileocolic artery
Middle colic artery
Right colic artery
What are the branches of the ileocolic artery?
Terminal ileal artery
Anterior caecal artery
Posterior caecal artery
Which artery is the appendicular artery a branch of?
Posterior ceacal artery
Which structures form the marginal arteries?
Both the midgut and hindgut
Which structure does the marginal artery supply?
The colon
What is the blood supply of the large intestine like and why?
Dual blood supply from both superior and inferior mesenteric arteries because some of the structures are derived from the midgut, and some others are from the hindgut
What are the branches of the inferior mesenteric artery related to the large intestine?
Left colic artery
Sigmoidal arteries
Superior rectal artery
What structures does the left colic artery supply?
Distal part of the descending colon
What structures do the sigmoidal arteries supply?
The sigmoidal colon
Where are the middle and inferior renal arteries derived from?
Internal iliac artery
Which veins are direct banches of the portal vein?
Splenic vein
Superior mesenteric artery
Which veins directly drain inro the portal vein?
Right gastric vein
Left gastric vein
Cystic vein
Which vein does the middle rectal vein drain into?
Internal iliac vein
Which vein does the inferior rectal vein drain into?
Internal pudendal vein
Which veins are part of the portosystemic anastomosis?
Superior rectal vein
Middle rectal vein
Inferior rectal vein
Which veins drain into the inferior mesenteric vein?
Left colic
Sigmoid
Superior rectal
Which are the veins that drain into the splenic vein? (4)
Left gastroepiploic
Short gastric
Pancreatic
Inferior mesenteric
Which are the veins that drain into the ileocolic vein?
Anterior cecal
Posterior cecal
Which veins drain into the superior mesenteric vein? (7)
Right gastroepiploic
Inferior pancreatiduodenal
Middle colic
Right colic
Ileocolic
Jejunal
Ileal
What are the layers of the large intestine?
Mucosa
Submucosa
Muscularis
Serosa
What are the layers of the mucosa of the large intestine?
Epithelium
Lamina propria
Muscularis mucosa
What is the histology of the epithelium of the mucosa of the large intestine?
Simple columnar
What are the cells found in the epithelium of the large intestine?
Absorptive cells
Goblet cells
Regenerative cells
Enteroendocrine cells
What is the main kind of cells in the epithelium of the large intestine?
Absorptive cells
What is the function of goblet cells in the large intestine and what happens to their number?
Lubricate the lumen and they increase in number as you go down the GIT
Why are regenerative cells crucial in the large intestine?
Needed because of the shedding
What is the layer of submucosa?
Submucosal plexus (Meissner)
What are the layers of the muscularis of the large intestine?
Inner circular
Myenteric plexus (Auerbach)
Outer longitudinal
What is the layer of the serosa of the large intestine?
Mesentery
Which muscle makes up the taenia coli?
Outer longitudinal
Which structure is the only one that is fully covered by outer longitudinal muscle?
The appendix
If you were to look at the mesoappendix cross-section, what would you see?
Appendicular artery
Why are there aggregate lymphoid nodules?
It is mainly formed from lymphoid tissue
What is the number of goblet cells like in the rectum?
The rectum is packed with goblet cells
What happens in the rectoanal junction?
Sudden change in the lining of the epithelium
The simple columnar epithelium with tubular intestinal glands in the rectum changes to stratified squamous epithelium in the anal canal
What is the epithelium of the anal canal like and what changes occur to it?
It will initially be non-keratinized and by the time it reaches the lower part (ectoderm), where it will change into keratinized
What is the mobility of the small intestine like?
Duodenum is the only non mobile structure
What is the mobility of the large intestine like?
Ascending and descending colons are fixed
What is the mesentery like in the small intestine?
Small intestine has a mesentery except of the duodenum
Which structures of the large intestine have mesenteries?
Appendix, transverse and sigmoid colons
What is the caliber of the intestines like?
Small intestine: smaller caliber
Large intestine: larger caliber
What is the longitudinal muscle of the intestines like?
Small intestine: continuous later
Large intestine: taenia coli
What is the fatty tags of the intestines like?
Small intetsine: has no fatty tags
Large intestine: Appendices epiploicae
What is the wall of the intestines like?
Small intestine: smooth
Large intestine: sacculated
What is the mucous membrances of the small intestine like?
Plucae circulares
Villi
Peyer’s patches
What are the mucous membranes of the large intestine like?
Absent
What is the pathology of aganglionic megacolon?
Hirschprung’s Disease
What is aganglionic megacolon?
Developmental disorder, characterized by the absence of the ganglia in the distal colon!!!!
What causes aganglionic megacolon?
Failure of migration of neural crest cells between 4th and 7th week of gestation
What is the result of aganglionic megacolon?
Results in functional obstruction
What is a megacolon?
Colon is dilated with feces and gases prior to obstruction
What is intussusception?
Telescoping of a proximal segment of the bowel into the lumen of an adjoining distal segment
What is the risk of intussusception?
Risk of cutting off the blood supply to the gut
Which population is intussusception common in?
Common in children
Which segment is most commonly affected by intussusception?
Ileocolic region
What is diverticulosis?
A common clinical condition where there is herniation of the lining of the mucosa through the circular muscle between the teniae coli
Where does diverticulosis occur?
At the point where circular muscle is the weakest
Why is it important to know the lymphatic drainage of an organ?
Important for metastasis in cancer and also infection spread
What does the lymph drainage usually follow?
The blood supply of an organ
Where does the anterior aspect of the diaphragmatic surface and part of the visceral surface of the liver drain its lymph?
Hepatic lymph nodes and then into celiac nodes
Where does the posterior aspect of the diaphragmatic surface and the rest of the visceral surface of the liver drain its lymph?
Phrenic lymph nodes, which communicate with mediastinal nodes
What is the lymph drainage of the large intestine? (8)
Middle colic
Right colic
Superior mesenteric
Ileocolic
Epiploic
Intermediate colic
Paracolic
Inferior mesenteric
What are the lymph nodes of the posterior abdominal wall?
Para-aortic and Preaortic
What structures do the preaortic lymph nodes drain?
GI tract from the lower 1/3 of the esophagus to halfway down the anal canal
Gallbladder
Pancreas
Greater part of the liver
Spleen
Why is it specifically only the greater part of the liver that drains into the preaortic lymph nodes?
The bare area is not drained in the preaortic lymph nodes
What are the different lymph drainage station of the preaortic lymph drainage?
Celiac
Superior mesenteric
Inferior mesenteric
Where ae the preaortic lymph nodes located?
Anterior to the aorta
What is the largest lymphatic channel in the body?
Thoracic duct
What does the thoracic duct originate from?
Cisterna chyli in the abdomen
Ascends through aortic hiatus
Where does the thoracic duct run into?
In the posterior mediastinum, between aorta, azygous vein and esophagus
What does the thoracic duct drain?
Junction of the left jugular and left subclavian vein and lower hepatic part
Which trunks does the thoracic duct receive?
Jugular, subclavian, and bronchomediastinal trunks
