Anatomy 3 Flashcards
Describe the oesophagus
Muscular tube - 25cm long and extends from the pharynx to the stomach. The abdominal part of oesophagus is only 1.25cm long.
What are the three constrictions of the oesophagus?
Cervical, thoracic and diaphragmatic
What is the vertebral level of the oesophageal opening (hiatus) in the diaphragm?
T10
What other structures other than the oesophagus that goes through the oesophageal hiatus in the diaphragm?
- L gastric vein
- L gastric aa.
- Vagus nerve
What is the blood supply to the abdominal part of the oesophagus?
Artery: Branches of L gastric artery
Vein: L gastric vein and azygous vein
What is the lymphatic drainage of the abdominal part of the oesophagus?
L gastric nodes and coeliac nodes
What is the clinical importance of the abdominal part of the oesophagus?
Important site for portosystemic anastomoses. in portal hypertension, the anastomoses open and forms venous dilatations called oesophageal varies. Their rupture causes severe and dangerous haematemesis (vomiting of blood)
Describe the stomach
It is a muscular bag forming the widest and most distensible part of the digestive tube. It has two orifices and openings, two curvatures and two surfaces.
What are the two orifices of the stomach??
Cardinal (from oesophagus) and pyloric (into duodenum)
What are the two curvatures of the stomach?
Lesser and greater curvature
What are the two surfaces of the stomach?
Anterior and posterior
What are the different parts to the stomach?
- Cardinal orifices
- Fundus
- Body
- Pyloric antrum
- Pyloric canal
- Duodenum
What is the pyloric sphincter?
Band of smooth muscle between stomach and duodenum (pylorus) which controls discharge of chyme into small bowel
Formed from the muscular external.
What is the clinical importance of the pyloric sphincter?
- Some are borne with congenital pyloric stenosis -> thickening of smooth muscle in the pylorus
- Carcinoma of stomach
- Gastric ulcers and vagotomy
Where is the lesser omentum?
Extends from lesser curvature of the stomach to the liver
Where is the greater omentum?
Greater curvature of the stomach to the transverse colon
Describe the interior of stomach
Contains gastric folds (rugae) which are formed from gastric mucosa and submucosa, and is the most apparent in the pyloric and greater curvature
What is the stomach bed?
The stomach lies on several structures in the abdominal cavity which forms the bed
- L dome of diaphragm
- L kidney
- Spleen
- Splenic artery
- Pancreas
- Colon
- Transverse mesocolon
Name the four primary lymph nodes which drain the stomach
- Gastric (superior) group
- Supra-pyloric group
- Pancreaticollenal group
- Inferior gastric sub-pyloric group
All eventually drain into the coeliac lymph nodes
What is the clinical importance of the 4 primary stomach lymph node groups?
Gastric carcinoma (Cancer) is common and occurs along the greater curvature.
What nerve is key in controlling gastric motility?
Vagus nerve
What is the effect of the stomach which vagal stimulation?
- Pylorus -> increased contraction
* Gastric secretion -> increased
What is the clinical importance of the vagus nerve innervation on the stomach?
The arrangement of vagal branches to the stomach allows for highly selective vagotomy to be used to treat over-active gastric acid secretion.
This denervates the funds and body, decreasing secretion, while the supply to the antrum remains so preserving essential gastric motility.
Describe the structure of the small intestine
- Extends from the pylorus of the stomach to the ileocecal junction
- Duodenum, jejunum and ileum
- Foregut/midgut boundary occurs in the 2nd part of the duodenum at the major duodenal papilla (also where duodenum receives the opening for pile and pancreatic duct)
What is the peritonisation of the different parts of the small bowel?
- Duodenum -> retroperitoneal
- Jejunum -> intraperitoneal
- Ileum -> intraperitoneal
Which part of the small intestine is the shortest, widest and most fixed part?
Duodenum
How does a duodenal ulcer form?
Inflammatory erosions of the duodenal wall (mostly 1st part)
What are the characteristics of the jejunum?
- Red
- Thick + heavy wall
- Great vasculature than ileum
- Long vasa recta
- Arcades are few large loops
- Few lymphoid nodules (Peyer’s patches)
- More fat in mesentery
- Circular folds are large, tall and closely packed
What are the characteristics of the ileum?
- Pink
- Thin and light wall
- Less vasculature
- Short vasa recta
- Many short loops in arcades
- Many lymphoid nodules (Peyer’s patches)
- More fat in mesentery
- Less and sparse circular folds, absent in distal part
What is the effect of the sympathetic system on the small intestine?
Reduces secretion and motility of the intestine and also causes vasoconstriction
Describe the blood supply to the midgut
Superior mesenteric artery
• Branch of abdominal aorta: L1
• Relations crossed anteriorly by splenic vein and neck of pancreas
• Mains branches: jejunal and ileal arteries
• Other branches : middle colic, R colic and iliocolic
What are the three features of the large intestine which distinguish it from the small intestine?
- Teniae coli
- Haustra
- Omental appendices
What is teniae coli?
Thickened bands of smooth muscle (longitudinal layer)
What is haustra?
Sacculations between teniae coli
What are omental appendices?
Small, fatty peritoneal like appendages
How are the different parts of the large intestine peritonised?
- Caecum -> intraperitoneal
- Ascending colon -> retroperitoneal
- Transverse colon -> intraperitoneal
- Descending colon -> retroperitoneal
- Sigmoid colon -> intraperitoneal
In what quadrant is the caecum and appendix is located?
R iliac region
What is the appendix?
Blind intestinal diverticulum with masses of lymphatic tissue
Variable in position in the body (retrocaecal most common)
What macburney’s point of the appendix?
Most common location of the appendix and is important as it is the site of maximum tenderness in acute appendicitis
What are two structures open into the cavity of caecum?
Appendix and ileum
What is the arterial supply to the three different parts of the rectum?
- Superior 1/3 -> Superior rectal aa
- Middle 1/3 -> middle rectal aa
- Inferior 1/3 -> inferior rectal aa
What is the venous supply to the three different parts of the rectum?
- Superior 1/3 -> Superior rectal vein
- Middle 1/3 -> middle rectal vein
- Inferior 1/3 -> inferior rectal vein
What is the peritonisation of the rectum?
- Superior 1/3 -> intraperitoneal
- Middle 1/3 -> retroperitoneal
- Inferior 1/3 -> subperitoneal
What is the role of the pelvic floor in maintaining faecal continence?
Keeps anus closed if defection not convenient
What other structures are involved in faecal continence?
Internal anal sphincter and external anal sphincter
What is the pectinate line?
It is a line which divides the upper 2/3 and lower 1/3 of the anal canal
Developmentally, this line represents the hindgut -> proctodeum junction
Which of the omentum are the heptoduodenal and hepagastric ligaments part of?
Lesser omentum
What is the falciform ligament and what structures lie within its free border?
Attaches liver to the anterior body wall and its free border contains the round ligament and para-umbilical veins
What structure in the free edge of the falciform iigament is a remnant of embryonic blood vessel?
The round ligament in the free border is also known as ligamentum teres, and it is a remnant of embryonic blood vessels, the umbilical vein
Describe the greater omentum
- 4 layers from GC of stomach to transverse colon
- Can be called abdominal policemen as it migrates to infected areas and absorbs bacteria and produces leukocytes for immune response
What are the paracolic gutters?
R + L parabolic gutters both lie laterally to the ascend and descending colon on the posterior body wall
They drain fluid that leaks from the colon (i.e. infectious matter, pus or bile) and prevents infection or damage to colon -> all drains to the pelvic area
Where are the parabolic gutters in relation to the large intestine?
Postero-lateral to ascending colon and descending colon
What are the abdominal viscera which lie in the free edge of a double layer of peritoneum described as the mesentery?
- Transverse colon (transverse mesocolon)
- Appendix (mesoappendix)
- Jejunum + ileum (mesentery proper)
Describe the histology of the oesophagus
- Epithelium: stratified squamous non-keratinised
* Muscularis externa: upper 1/3 skeletal, middle 1/3 smooth + skeletal and the lower 1/3 is smooth
Describe the histology of the stomach
• Simple columnar epithelium • Large folds in wall -> rugae • Gastric glands in mucosa: - Cardiac (mucous) - Fundic: HCL + intrinsic factor - Pyloric: gastrin • 3 layers of muscle in muscular external (oblique muscle)
What do gastric pits contain?
The pits contain surface mucous cells
And the glands that they continue on as contain:
• Parietal cells: secrete HCl
• Chief cells: secrete pepsinogen
What are the large folds that you can see extending into the lumen called?
Plicae circulares (mucosal folds) which each have villi processes
What is the epithelium of the small intestine?
Simple columnar
Describe the glands in the small intestine
Glands in the lamina proprietary do not extend beyond the muscular mucosae (international’s)
Where in the GI tract do the glands extend beyond the muscularis mucosae (interna) and into the submucosa?
Oesophagus and duodenum
What are the secretory cells in the small intestine and what do they secrete?
Goblet cells and secrete mucous
What types of cells are in the epithelium of the small intestine?
Enterocytes (absorptive cells) and goblet cells
What is a Peyer’s patch and where are the found ?
Large lymphoid nodules in the submucosa of the small intestine
Describe the histology of the colon
- Simple columnar epithelium for absorption
- Thick mucosa has deep crypts, but there are no villi - The crypts of Lieberkühn are straight and unbranched and lined largely with goblet cells and stem cells at base
- Epithelium many goblet cells, endocrine cells and basal stem cells, but no Paneth cells
What are the main cells in the epithelium of the large intestine?
Goblet cells
What is the change in epithelium in the recto-anal junction?
From the simple columnar epithelium of the intestine to the keratinised stratified squamous epithelium of skin
