Anatomy Flashcards Preview

GI > Anatomy > Flashcards

Flashcards in Anatomy Deck (206):

What components of the GI tract are found in the head and neck

Head = oral cavity & pharynx
Neck = pharynx & oesophagus


What components of the GI tract are found in the chest



What components of the GI tract are found in the abdomen

Small intestine
Large intestine (mostly)
Most accessory organs


What components of the GI tract are found in the pelvis and perineum

Anal canal


What are the 4 functions of the upper GI tract

Mastication (chewing) - breaks down food
Taste - protective
Deglutition (swallowing) - passes food to stomach
Salivation - allows food to slide without causing trauma


What parts of the GI system are involved in mastication (may be accessories)

Temporomandibular joint
Muscle of TMJ, face and tongue


What parts of the GI system are involved in deglutition (may be accessories)



Describe mastication

The process of chewing
Function is to breakdown food
Facilitates taste and digestion (mixes food with saliva)
Carried out by movement of the jaw and tongue


what is the buccinators

muscle inside the cheek
it contracts to move food from one side of the mouth to the other


Describe the adult dentition

32 teeth
Divided into 4 quadrants (upper & lower R&L)
All present by 18y/o
2 inscisors
1 canine
2 pre molars
3 molars (1 is the wisdom tooth)


Describe the functions of the different types of teeth

Incisor - cutting
Canine - piercing and ripping meat
Premolars - transition (both)
Molars - grinding


Describe the temporomandibular joint

The mandible has a 'bump' called the condylar process
This sits in the mandibular fossa, posterior to the articular tubercle
This creates the joint


Which nerve supplies the muscles of mastication

Mandibular division of the trigeminal nerve
This is the only division with motor function


Name the muscles that cause closure of the jaw

Temporalis m. - connects coronoid process to temporal fossa
Masseter m. - angle of mandible to zygomatic arch
Medial Pterygoid - angle to pterygoid plates of sphenoid bone


Name the muscles that open the jaw

The lateral pterygoid
Connects condyle of mandible to pterygoid plates of sphenoid bone


why are less muscles required to open the jaw than to close it

Force of gravity
Jaw can fall open with gravity and help from one muscle


Describe the structure and function of the discs in the temporomandibular joints

There is an articular disc that separates the joint into 2 cavities - superior and inferior
Inferior allows rotation of joint
Superior allows translation


Describe the course of the mandibular division

Comes from the pons
Passes through the foramen ovale
Supplies the muscle of mastication and sensory area
sensation is supplied to jaw, teeth and in front of ear


List the structures in the oral cavity

Hard palate
Soft palate & Uvula
Palatine tonsils
Muscle of floor of the mouth


How is the tongue divided

Anterior 2/3
It is the horizontal part & is found in the oral cavity
Posterior 1/3
It is the vertical part & is found in the oropharynx
Divided by the sulcus terminalis


Which nerves supply the different parts of the tongue

Both taste and general sensation in posterior section are caused by CNIX
In anterior section taste is caused by CNVII and general sensation by CNV3


Describe the papillae

4 types, 3 of which are responsible for taste
Filiform - at front of tongue & senses touch, temp
Fungiform - middle of tongue
Vallate - large & near sulcus
Foliate - side of tongue


Describe the course of the facial nerve

Starts at pontomedullary junction (between pons & medulla)
Travels through temporal bone via internal acoustic meatus then stylomastoid foramen
Supplies anterior 2/3 of tongue (taste), facial muscles
Connects to CNV3 and follows to supply glands in floor of mouth


Which nerves give sensation to the oral cavity

Superior half is supplied by CNV2
Inferior half is by CNV3


What is the function of the gag reflex

Protective reflex that prevents foreign bodies from entering the pharynx or larynx


What nerves cause the gag reflex

the sensory part of reflex is carried by CNIX
The motor part by CNX mostly and CNIX


Describe the course of the maxillary division of trigeminal nerve (CNV2)

These are sensory fibres
Start at pons
Pass through foramen rotundum which points down and forward
innervates the mid face – sensation only


Describe the course of the glossopharyngeal nerve (CNIX)

Starts at the medulla
Passes through jugular foramen and courses forward
Supplies the posterior wall of oropharynx (sensory), parotid gland (secretomotor) and post. 1/3rd tongue (sensation and taste)


Name the 3 salivary glands and state where they are and where they secrete into the mouth

Parotid- crosses face and secretes by the upper 2nd molar
Submandibular- under jaw & enters floor of mouth
secretes via lingual caruncle
Sublingual - floor of mouth and secretes via several ducts above it


What nerve supplies each salivary gland

Parotid = CNIX
Submandibular and sublingual = CNVII


Name the 4 extrinsic muscles of the tongue



What is the function of the extrinsic muscles of the tongue

Change the position of the tongue during mastication, swallowing and speech


What nerve supplies the muscles of the tongue

All are innervated by the hypoglossal nerve with the exception of the palatoglossus


Describe the intrinsic muscles of the tongue

There are 4 pairs
Located dorsally/posteriorly
Modify the shape of the tongue during function


Describe the course of the hypoglossal nerve (CNXII)

Starts at medulla
Passes through hypoglossal canal
Supplies the extrinsic & intrinsic muscle of tongue (except palatoglossus)


Describe the circular muscles of the pharynx

3 sets
Voluntary muscles
Also known as constrictor
Innervated by CNX
Form the external muscle layer and overlap each other
Contract sequentially


Describe the longitudinal muscles of the pharynx

There are 3
Form the inner layer
Supplied mainly by CNX and one by CNIX
Elevate the larynx towards the epiglottis during swallowing to close laryngeal inlet


What is an endoscope and how is it inserted

Device used to view inside of the GI tract
Ask patient to swallow as you insert it to get it into the tract


Describe the action of swallowing (mouth to oesophagus)

Lips are closed - uses orbicularis oris CNVII
The tongue pushes bolus back towards oropharynx - uses CNXII
The pharyngeal constrictor muscles contract sequentially (using CNX) to push bolus down to oesophagus
At the same time the longitudinal layer contract to close laryngeal inlet - uses CNIX & X
The bolus then passes to oesophagus


Is swallowing a voluntary process

The initiation of the swallowing action is voluntary
All muscles involved are skeletal but once initiate it cant be stopped


Describe the course of the oesophagus

In neck it moves posterior to trachea and anterior to vertebral bodies
In chest it moves posterior to heart and is in contact with left atrium
Then in abdomen it passes through diaphragm and connects to the stomach


What are the 3 physiological (normal) constrictions of the oesophagus

Cervical - caused by cricopharyngeus muscle (the sphincter)
Thoracic - caused by arch of aorta & left main bronchus
Diaphragmatic - caused by passage through diaphragm (lower sphincter)


What effect can dilation of the left atrium have on the oesophagus

It can cause dysphagia (difficulty swallowing) as it puts pressure on the oesophagus


Describe the lower oesophageal sphincter

Caused by passage through diaphragm not an actual anatomical feature
Sphincter effect produced by contraction of diaphragm, intrabdominal pressure being higher than intragastric and the oblique angle that oesophagus enters stomach at


What is the function of the lower oesophageal sphincter

Helps reduce reflux from the stomach


What is the Z line

Transition point of oesophageal mucosa to the stomach mucosa
Very obvious change that can be seen on endoscope


Name the structural points of the stomach

Fundus is the superior part
Cardia is immediately at point where oesophagus joins
Body is the main part of stomach
Rugae are the folds of the inner wall
Pyloric antrum is the section just before the pyloric sphincter

The lesser curvature is the 'inside' of the J shape and greater curvature is outside
The Incisura angularis
is the angle of the J


What is the purpose of the rugae in the stomach

Folds in the inner lining of the stomach that allows expansion of the stomach


Which abdominal regions is the stomach usually found in, in supine patients

Left hypochodrium, epigastric and umbilical regions


What are the different sections of the small intestine



What are the different sections of the large intestine

Ascending colon
Hepatic flexure
Transverse colon
Splenic flexure
Descending colon
Sigmoid colon
Anus & anal canal


Which organs are considered part of the foregut

oesophagus to mid-duodenum
Liver & gall bladder
1/2 of the pancreas


Which organs are considered part of the midgut

Mid-duodenum to proximal 2/3 of transverse colon
1/2 of pancreas


Which organs are considered part of the hindgut

Distal 1/3 of transverse colon to proximal 1/2 of anal canal


What are the 4 quadrants of the abdomen

right and left upper
right and left lower


what are the 9 abdominal regions - left to right, top to bottom

R hypochondrium
L hypochondrium
R lumbar
L lumbar
R inguinal
L inguinal


What is guarding

When the abdomen becomes rigid if there is irritation/inflammation to protect the organs underneath


Name the abdominal muscles

external oblique (hands in pocket orientation), internal oblique, transversus abdominus and the rectus abdominus


What is the peritoneum

A thin, transparent, semi-permeable, serous membrane
Lines the walls of the abdominopelvic cavity and organs
Continuous membrane with parietal layeron body wall and the visceral surrounding the organs
Creates peritoneal cavity between layer
Contains lubricating fluid


What causes peritonitis

Blood, pus or faeces getting into the peritoneal cavity can cause severe inflammation
In women, infection in the reproductive tract can pass up into the peritoneum


Define the intraperitoneal organs

Almost completely covered in visceral peritoneum
Minimally mobile


Define the retroperitoneal organs

Only has visceral peritoneum on its anterior surface
Located in the retroperitoneum


Define the organs that have a mesentery

Covered in visceral peritoneum
Visceral peritoneum wraps behind the organ to form a double layer – mesentery
Mesentery suspends the organ from the posterior abdominal wall – very mobile


What organs/structures are considered retroperitoneal (SAD PUCKER)

S: suprarenal (adrenal) gland
A: aorta/IVC
D: duodenum (second and third part)
P: pancreas (except tail)
U: ureters
C: colon (ascending and descending)
K: kidneys
E: oesophagus
R: rectum


What organs are intraperitoneal

Liver + gall bladder
Parts of small intestine
Transverse colon


What are the 3 types of peritoneal formations

Omentum (greater and lesser)
Peritoneal ligaments


Describe the mesentery

Double layer of visceral peritoneum that connects organ to the body wall
Gives lots of motility
It has a core of connective tissue, blood, lymph and nerve supplies
There is the mesentery proper of the small intestine
Transverse and sigmoid mesocolon
and the mesoappendix


Describe the greater omentum

Layers double back on themselves to creates pouches (greater and lesser sac)
Hangs like an apron over organs
Attaches the greater curvature of stomach to transverse colon


Describe the lesser omentum

double layered
Runs between lesser curvature of stomach and duodenum to liver
Has a free edge


What is the omental foramen

Point of communication between the greater and lesser sacs
Also called foramen of Winslow


what makes up the portal triad

The hepatic artery, the hepatic portal vein, and the hepatic ducts (bile ducts)


Name 4 key peritoneal ligaments

Hepatogastric - connects stomach to liver
Hepatoduodenal - connects duodenum to liver
Gastrosplenic - connects spleen to stomach
Splenorenal - connects kidney to spleen


Describe the pouches formed by the inferior part of the peritoneum

Drapes over pelvic organs, forms pouches
Fluid can gather there
One in men - rectovesical between bladder and rectum
Two in women - vesico-uterine pouch (between bladder and uterus) and the recto-uterine pouch/ pouch of Douglas (uterus-rectum)


What is ascites

Collection of fluid in the peritoneal cavity


What can cause ascites

Cirrhosis - reduces functionality of liver and blood backs up in hepatic system so fluid is pushed out
Portal hypertension


How is ascites treated

Fluid must be drained from the cavity by paracentesis
Place needle lateral to the rectus sheath to avoid the inferior epigastric artery
May need ultrasound guidance


What 4 questions should you ask about abdominal pain

Pain referral pattern


Describe the difference in location and character of visceral and parietal pain

Location: Visceral pain is hard to localise, somatic pain is easier
Character: Visceral pain tends to be dull, achy & nauseating
Somatic pain tends to be sharp and stabbing


What is colicky pain

Pain that comes and goes
Common in GI problems


List the nerves that supply the organs of the abdomen

Visceral afferents - sensory & transmit pain
The enteric nervous system
Autonomic motor nerves - parasympathetic and sympathetic


List the nerves that supply the abdominal walls

Somatic sensory nerves
Somatic motor nerves
Sympathetic nerve fibres


How do sympathetic nerve fibres get from the CNS to the abdominal organs?

Leave the spinal cord between levels T5 and L2
(thoraco-lumbar outflow)
Enter the sympathetic chains (bilaterally) but do not synapse
Leave the sympathetic chains within abdominopelvic splanchnic nerves
Synapse at prevertebral ganglia which are located anterior to the aorta at the exit points of the major branches
Postsynaptic sympathetic nerve fibres pass from ganglia onto the surface of arteries which they 'piggyback' to the organs


Name the 4 prevertebral ganglia

Superior mesenteric
Inferior mesenteric


How do sympathetic nerve fibres get to the adrenal gland

Leave the spinal cord at T10-L1
Enter the abdominopelvic splanchnic nerves
Don't synapse at the prevertebral ganglia
Are carried with periarterial plexuses to the adrenal gland
Synapse directly onto cells


Which parasympathetic nerves supply the abdominal organs

Vagus nerve - CNX
Pelvic splanchnic nerves - S2,3,4,
It is a cranial-sacral outflow


How does the vagus nerve supply the abdominal organs

presynaptic fibres enter abdominal cavity on surface of the oesophagus (“vagal trunks”)
Go into the periarterial plexuses around the abdominal aorta
Then carried to the walls of the organs where they synapse in ganglia
Supply parasympathetic nerve fibres to the GI tract + abdominal organs up to the distal end of the transverse colon


How do the pelvic splanchnic nerves supply the abdominal organs

Presynaptic fibres leave spinal chord at S2,3,4
Supply the smooth muscle/glands of the descending colon to anal canal


In which abdominal region is pain from the foregut usually felt



In which abdominal region is pain from the midgut usually felt



In which abdominal region is pain from the hindgut usually felt



Where do foregut structures enter the spinal chord and how does this affect pain

Pain signals from this level will be associated with the dermatomes that are supplied by T6-9


Where do midgut structures enter the spinal chord and how does this affect pain

Pain signals from this level will be associated with the dermatomes that are supplied by T8-12


Where do hindgut structures enter the spinal chord and how does this affect pain

Pain signals from this level will be associated with the dermatomes that are supplied by T10-L2


How is abdominal pain referred

Pain signals from abdominal organs often get mistaken for signals from the associated section of the body wall (dermatomes)
This is because the nerves enter the spinal cord at the same levels
For example, liver/gall bladder can refer to the shoulder


Name the abdominal body wall nerves

Thoracoabdominal nerves- 7th -11th intercostal nerves
Subcostal nerve - anterior ramus of T12
Iliohypogastric nerve - half of L1 anterior ramus
Ilioinguinal nerve - other half of L1 anterior ramus


how does the pain appendicitis present

Initially a dull, ache in the umbilical region
Starts as visceral pain due to inflamed visceral peritoneum
As it progresses it becomes a sharper pain in the right iliac fossa
Irritations moves to parietal peritoneum and becomes somatic pain


What is jaundice

Yellowing of the sclera (whites of eyes) and skin due to an increase in bilirubin in the blood


What is bilirubin

By-product of the breakdown of red blood cells
It's used to form bile


What is the function of the gall bladder

Stores and concentrates bile when not eating
Releases it via the cystic duct when required


Describe how bile travels in the body

Produced in the liver
Passes down the biliary tree to the 2nd (vertical) part of the duodenum
Or backs up and is stored in the gall bladder


What are the main functions of the liver

Receives nutrients from GI tract
Glycogen storage
Bile secretion - constant process
Other metabolic functions


List the anatomical relations of the liver

Inferior to the right hemi-diaphragm
It's anterior and superior to the gall bladder
It's superior to the hepatic flexure
It's anterior to the right kidney, right adrenal gland, IVC, abdominal aorta
Its anterior to the stomach on the mid/left side


Where is the liver located

Mainly in the right upper quadrant
Protected by ribs 7-11
Adhered to the diaphragm so moves when breathing


Name the 4 anatomical lobes of the liver

Right lobe - largest
Left lobe
Caudate lobe - posterior surface
Quadrate lobe


What is the porta hepatis

Site of entrance for the hepatic portal structures
e.g. blood enters & leaves via this


Describe the functional anatomy of the liver

Split into 8 functional segments
Each has its own branch of a hepatic artery, portal vein, bile drainage and venous drainage


What structures do the hepatic veins and IVC lack and why is this significant

They don't contain valves
Any increase in venous pressure will affect the liver


What structures are found in the portal triad

Hepatic portal vein - most posterior
Hepatic artery proper - in front of vein
Bile duct


Describe the coeliac trunk

First midline branch of abdominal aorta - leaves at T12 level
Retroperitoneal structure
Supplies organ of the foregut
Trifurcates into: splenic, left gastric and common hepatic arteries


When does the common hepatic artery become known as the hepatic artery proper

Once it has given off the gastroduodenal artery


Describe the course of the left gastric artery

Runs in the lesser curvature of the stomach


Describe the course of the splenic artery

Very tortuous course
Runs posterior to stomach and along the superior border of the pancreas


Describe the anatomical relations of the spleen

Diaphragm is posterior
Stomach is anterior
The splenic flexure is inferior
The left kidney is medial to it


Describe the location of the spleen

Intraperitoneal organ
Found in left hyperchondrium/left upper quadrant
Posterior to the mid axillary line
Protected by ribs 9-11 - fracture of these can rupture the organ


What is the function of the spleen

Storage system for blood - therefore causes significant internal bleeding if damaged
Breaks down red blood cells - produces bilirubin


List the major blood supplies to the stomach

Right and left gastric arteries which anastomose - found between lesser curvature & lesser omentum
Right and left gastro-omental arteries which also anastomose - found between greater curvature and lesser omentum


Describe the blood supply to the liver

Has a dual supply
Majority comes from the hepatic portal vein
Rest comes from the right and left hepatic arteries (branched of hepatic artery proper)


What is the clinical significance of the hepatorenal recess

Lowest part of the peritoneal cavity when lying down
Fluid/pus will therefore collect in this recess when supine


What vessels form the hepatic portal vein

The splenic vein (drains foregut) and the superior mesenteric vein (midgut)
The inferior mesenteric (drains hind) joins into the splenic


Describe the blood supply to the gall bladder

Supplied by the cystic artery
This branches of the right hepatic artery in most people - can vary
Found in the triangle of calot


What forms the triangle of calot

the cystic duct on the left
The common hepatic duct on the right
Inferior border of liver forms the top of the triangle


Name the parts of the gall bladder (top to bottom)

Cystic duct


How does gall bladder pain present

Visceral afferents enter spinal cord at T6-9 so presents in epigastric region
Can also present in hypochondrium with referral to the shoulder if it irritates the anterior diaphragm


What is a cholecystectomy

Surgical removal of the gall bladder


Describe the parts of the biliary tree

Made up of several ducts
Right and left hepatic ducts come from respective lobes of the liver
Combine to the common hepatic duct
Cystic duct transports bile to and from gall bladder and will combine with the common hepatic to form the (common) bile duct


Name the 4 parts of the duodenum

Superior - has duodenal cap


Is the duodenum retroperitoneal

All parts apart from the superior are


What is the role of CCK

Peptide hormone secreted by the duodenum
Released when fat is present
travels through the blood and stimulates contraction of the gall bladder to release bile


Where does pain from the duodenum tend to present

Epigastric region


Describe the structure of the pancreas (different sections)

Has a head with uncinate process


Describe the anatomical location of the pancreas

Lies transversely across the posterior abdomen - retroperitoneal
It sits anterior to the right kidney & adrenal gland, IVC, bile duct, abdominal aorta, superior mesenteric vessels, left kidney & adrenal gland and part of the portal venous system
It sits posteriorly to the stomach
The duodenum surrounds the head
It sits above and in front of the splenic vessels


What is the function of the pancreas

Has both endocrine and exocrine functions
Endocrine - islets of Langerhans secrete insulin and glucagon
Exocrine - acinar cells secrete pancreatic digestive enzymes into the duct


What stimulates the acinar cells to produce enzymes

The parasympathetic nervous system


Describe the path of the common bile duct

Descends posteriorly to the superior part of the duodenum
travels in a groove on the posterior aspect of the pancreas
joins with the main pancreatic duct to form the ampulla of vatar
There is a sphincter at the join


Describe the pancreatic duct(s)

Main pancreatic duct runs the whole length of the pancreas
In some people there is an accessory duct that drains to the minor papilla
The main duct has a sphincter and then joins the ampulla of vatar with the bile duct


Describe of the ampulla of vatar drains into the duodenum

Ampulla is a widened part of the duct which combines the contents of the pancreatic and bile duct
This drains into the 2nd part of the duodenum via the major papilla


What is ERCP

An investigative technique where you insert an endoscope into the duodenum
A cannula is then pushed into the major papilla to inject dye into the biliary tree
Radiography can then be used to gain images of the vessels (liver & pancreas)


How does obstruction of the biliary tree cause jaundice

Obstruction can be caused by gall stones or carcinoma at the head of the pancreas
Bile flows back up to the liver as it cannot be released
This causes bile to spill over into the blood and that's how bilirubin turns you yellow


What happens if the pancreatic duct gets blocked

Digestive enzymes can back up into the pancreas and cause pancreatitis


Describe the blood supply of the duodenum and pancreas

The coeliac trunk produces the splenic artery which has branches that supply the pancreas - dorsal pancreatic
It also produces the common hepatic which branches to the gastroduodenal artery
This then branches to the superior pancreaticoduodenal artery
This anastomoses with the inferior pancreaticoduodenal which is a branch of the superior mesenteric artery


How does pancreatic pain present

It is a foregut and a midgut organ so can present in the epigastric and umbilical region
sometimes it can radiate through to the patients back due to dermatome association


What is a common sign of acute pancreatitis

Vascular haemorrhage - severe bruising
Blood pools in the flank or around the umbilicus as the
pancreas is retroperitoneal


What are some of the main differences between the jejunum and ileum

Colour - J is deep red, I is lighter pink
Wall - J is thicker and heavier than I
Vascularity - J is more vascular than I
Mesenteric fat - I has more fat than J
Circular folds - J has large, tall folds whilst I is low and sparse
Lymphoid tissue - present in I but not J


What is the blood supply of the jejunum and ileum

Arterial blood comes from superior mesenteric via the jejunal and ileal arteries
Venous drainage is by the jejunal and ileal veins which drain to superior mesenteric and then the hepatic portal vein
The vasculature is found in the mesentery


Describe the course of the superior mesenteric artery

leaves aorta at L1 level
Travels posterior to the neck of the pancreas
Then inferiorly, anterior to the uncinate process
It then enters the mesentery proper and branches out


Describe the absorption of fat

Bile helps with the absorption by emulsifying the fat into droplets (chylomicrons)
These are absorbed into the intestinal cells where they are passed into the lymphatic system via the lacteals
Eventually will drain into the venous system


Name the main groups of lymph nodes that drain the abdominal organs

Celiac - drains foregut organ
Superior mesenteric - midgut
Inferior mesenteric - hindgut Lumbar - posterior wall, pelvis and lower limbs


where does all lymph drain to

Superficial vessels drain into deep ones
3/4 of the body drains into the thoracic duct which then drains at the left venous angle
The other 1/4 drains into the right lymphatic duct which drains at the right venous angle


What are the functions of the large intestine

Defence – commensal bacteria
Absorption – H2O & electrolytes
Excretion – of formed stool


What are the paracolic gutters

There are 2 - left and right
Found between lateral edge of ascending and descending colon, and abdominal wall
Small gaps that are part of the greater sac
Potential sites for pus collection


What are the tenaie coli

The 3 distinct longitudinal bands of muscle in the large intestine


Which of the colon flexures are higher

The splenic
The liver pushes the hepatic one lower


What are haustra

Small pouches that give the colon a segmented appearance
Characteristic of large intestine


Describe the position of the appendix

In right iliac fossa
Most often retrocaecal but there are variations


What is McBurney's point

1/3 between right ASIS and the umbilicus
Point on the body which will be most tender in someone with appendicitis


What is the significance of the sigmoid colon having a long mesentery

Allows it to move more
This gives risk of it twisting around itself - sigmoid volvulus
This results in obstruction and potentially infarction


List the branches of the abdominal aorta

Midline: coeliac trunk, superior mesenteric artery & inferior mesenteric
Lateral branches: renal (kidneys & adrenals), gonadal (testes/ovaries) and the lumbar (body wall)
Bifurcates into common iliac arteries


At what level does the abdominal aorta bifurcates

Splits into the common iliac arteries at L4


List the braches of the superior mesenteric artery

Right colic
Middle colic
Inferior pancreaticoduodenal

Supply ascending and transverse


What are the differences between the jejunal and ileal arteries

Jejunum has longer vasa rectae (straight arteries) and larger, fewer arcades compared to the ileal


List the branches inferior mesenteric artery

Left colic
Sigmoid arteries (several)
Superior rectal

Supply descending, sigmoid and rectum


What is the marginal artery of Drummond

The blood vessel that anastomoses the SMA and IMA
It provides an alternative route for blood and helps prevent ischaemia


What level is the SMA found at

Branches off aorta at L1


What level is the IMA found at

Branches off aorta at L3


Describe the blood supply to the rectum and anal canal

Superior rectal artery (branch of IMA)
The middle and inferior rectal arteries which are branches of the internal iliac artery


List the veins of the gut organs and what they drain

Inferior mesenteric - drains hindgut to splenic vein
Superior mesenteric - drains midgut to the portal system
Splenic vein - drains foregut to hepatic portal
Hepatic portal - drains all areas to the liver
IVC - drains blood from portal system to the right atrium


what at the 3 sites of anastomosis between the systemic and portal system

In the distal end of oesophagus - connects hepatic portal and azygous
In the skin around umbilicus - connects paraumbilical and epigastric
Around rectum and anal canal - connects IMV and internal iliac


What is the clinical significance of the anastomosis between the systemic and portal system

If the liver is blocked or at too high pressure the blood can travel back (the collateral veins have no valves) and enter the systemic system
This allows blood to get back to the heart via a different routes


What is portal hypertension

Elevated blood pressure in the portal system (blood vessels of the liver)


What can cause portal hypertension

Liver pathology such as cirrhosis
A tumour compressing the hepatic portal vein


What are the effects of portal hypertension

Leads to a reversal of blood flow
Larger volume of blood flow through anastomotic vessels causes them to become varicosed


What are the clinical presentations of portal hypertension

Oesophageal varices - vomit blood
Caput medusae - dilated veins around umbilicus
Rectal varices - rectal bleeding


What is hematemesis and some potential causes

Vomiting up blood
Could be caused by peptic ulcer or ruptured varices


What is required for the control of excretion of faeces

The rectum - acts as holding area
Visceral afferent fibres - sense fullness
Functioning muscle sphincters
Normal cerebral function to control timing of defection


What is the function of the rectum

Acts as a holding area for faeces until it is appropriate to defecate
Has lots of stretch receptors in the walls to sense fullness - it stretches when full
This sends signal to brain via visceral afferents


How can nerve damage affect continence

after a stroke, dementia, spinal cord injury some control of muscles is lost
This means you have less control over your sphincters and more likely to be incontinent


Which factors can affect continence

Degeneration of nerves associated with age
Consistency of stool


Where is the pelvic cavity located

Within the bony pelvis, between the pelvic inlet and pelvic floor
Continuous with abdominal cavity - separated by peritoneum
Contains the pelvic organs and tissues - includes rectum


What is the function of the pelvic floor

Keeps the organs in the body - support & strength has opening to allow GI, renal and reproductive organs to reach the perineum


how many passages are in the pelvic floor

3 in women (bladder, uterus, rectum)
2 in men (bladder, rectum)


Which parts of the GI tract are found in the pelvis and perioneum

Anal Canal


At what level does the sigmoid colon become the rectum

Recto-sigmoidal junction


Where does the rectum become the anal canal

Anterior to the coccyx
Just before passing through the levator ani


Describe the structure of the rectum

Has 3 lateral folds as it descends - allows for stretching
Muscular walls
Has an ampulla - wider region to accommodate faeces storage
2 functional sphincters


List the anatomical relationships of the rectum

Most posterior organ Superior part is covered in peritoneum
Superior portion lies posterior to the Rectouterine/rectovesical pouch
Inferior part lies posterior to the prostate in men and vagina+cerivx in women


Describe the levator ani

It is composed of 3 muscles and forms most of the pelvic diaphragm (pelvic floor)
Forms roof of the perineum
Made of skeletal muscle
Provides support for the pelvic organs
Contracts during coughing/sneezing
Relaxes to allow defection


What 3 muscles make up the levator ani



What nerves supply the levator ani

'nerve to the levator ani' - branch of sacral plexus
pudendal nerve - S2,3,4


Describe the puborectalis

skeletal muscle that's part of levator ani
Important for maintaining continence
Contraction decreases anorectal angle which acts like a sphincter - keeps faeces in rectum until voluntary release


Describe the internal anal sphincter

Made of smooth muscle and is involuntary
Controls superior 2/3 of anal canal
Contraction is stimulated by sympathetic and inhibited by the parasympathetic
Contracted most of the time to maintain continence - only relaxes when rectum is full


Describe the external anal sphincter

Made of skeletal muscle and is voluntary
Controls inferior 2/3 of anal canal
Contraction is stimulated by pudendal
Voluntarily contracts when the rectal ampulla is distended (full) and the internal is relaxed


What types of nerves control structures in the pelvis

Visceral afferents


What types of nerves control structures in the perineum

somatic motor and sensory nerves


Which nerves supply the rectum/anus from T12-L2

Sympathetic fibres
Contract internal sphincter & inhibit peristalsis


Which nerves supply the rectum/anus from S2-4

Visceral afferents, parasympathetic and somatic motor


What damage can occur during labour

The pudendal nerve can be stretched or snapped
Muscle fibres in the puborectalis or external sphincter can be torn
These can both lead to incontinence


What is the pectinate line

Junction between the initial endoderm and ectoderm layers - from development
everything above line is derived from endoderm and everything below was ectoderm,


List the nerve, blood and lymph supplies to above the pectinate line

Nerve - autonomic
Arterial - Inferior mesenteric
Venous - hepatic portal system
Lymph - inferior mesenteric nodes


List the nerve, blood and lymph supplies to below the pectinate line

Nerve -somatic and pudendal
Arterial - Internal iliac
Venous - systemic venous system
Lymph - superficial inguinal nodes


List the main groups of lymph nodes that drain the pelvic organs

Internal iliac - drain inferior structures
external iliac - drain superior structures & limbs
Common iliac - drain from internal & external
Lumbar -collects lymph from common


List the arteries that supply the rectum and anal canal

Superior rectal artery
Internal iliac artery
middle rectal artery
Inferior rectal artery


List the veins that drain the rectum and anal canal

Inferior rectal vein
Middle rectal vein
These both drain into the internal iliac vein
Superior rectal vein which drains into the inferior mesenteric vein


What are rectal varices

Dilation of veins around the rectum due to increases pressure in the portal system
Can rupture and cause rectal bleeding


What are haemorrhoids

Prolapses of the venous plexuses in the rectum
Caused by raised pressure caused by muscle contraction e.g. labour or defecation
Can be internal or external - ex will cause severe pain


What are the ischioanal fossae

fossa on either side of the anal canal which are filled with fat and connective tissue
They communicate posterior to the canal
Can get infected and ischioanal abscesses can form


What different scopes can be used to examine the distal portions of the GI tract

Proctoscopy - views rectum
Sigmoidoscopy - views sigmoid colon (longer)
Colonoscopy - views interior of the colon