B3 Anatomy & Histology of GI Tract Flashcards
What forms the roof of the mouth?
Hard and soft palates
What forms the floor of the mouth?
Mylohyoid muscle
True or false? The tongue is the floor of the mouth
False - it’s superior to the hammock-shaped mylohyoid floor
What form the lateral walls of the mouth?
Cheeks
What forms the anterior of the mouth?
Lips
What is the posterior part of the mouth?
Palatoglossal floor
What structures are responsible for the mouth having two distinct spaces?
Teeth
What does the oral cavity refer to?
The whole mouth
What is the vestibule of the mouth?
Space between lips and teeth (run tongue along front of teeth)
What does the oral cavity proper refer to?
The region of the mouth enclosed by the teeth
What are the teeth and gums collectively known as?
Gingivae
What is the parotid gland?
The biggest salivary gland
What does the parotid gland secrete?
Serous secretions
Where is the parotid gland?
Posterior to the ramus of the mandible
Where is the submandibular gland?
Inferior to the angle of the mandible
Where is the sublingual gland?
Between the mylohyoid muscle and tongue
How long are the parotid and submandibular ducts?
5cm
Where does the submandibular gland lie?
Outside the mouth
Why are the openings of glands important?
You can occlude their secretions
What is the most anterior fold at the back of the mouth?
Palatoglossal fold
What is the most posterior fold of the mouth?
Palatolaryngeal fold
What structure is found between the folds of the mouth?
Tonsila fossa
What structures exist in the tonsila fossa?
Palatine tonsils
How long is the oesophageus?
25 cm
Where does the oesophageus run down?
C6- T10
What are the two sphincters associated with the oesophageus?
Upper
Lower
When does the upper oesophageal sphincter relax?
During swallowing
True or false? The upper oesophageal sphincter is voluntary
True - Think Harry Houdini
What is the lower oesophageal sphincter also known as?
Cardiac sphincter
What is the strength of the lower oesophageal sphincter?
Weak - needs the diaphragm to hold and support it.
Why is the oesophageal sphincter necessary?
Prevents gastro- oesophageal reflux
What type of epithelium is in the stomach?
Non-keratinised simple squamous epithelium
When would you get keratinised epithelium in the stomach?
Long standing mutation
What type of epithelium is at the top of the oesophageus?
Stratified squamous
What is the change in colouration histologically?
Histological junction- Pale pink (stacked epithelium) to briliant red (simple squamous)
What is the histological junction of the GI tract referring to?
Oesophageus - stomach Pale pink (stacked epithelium) to briliant red (simple squamous)
What is the stomach?
A proximally fixed muscular bag in the left upper quadrants
What is the lining of the stomach?
Peritoneal
What is the arterial supply of the stomach?
Coeliac trunk
What are the lymphatics of the stomach bed?
Coeliac nodes
What is the sympathetic nervous system’s association with the stomach?
Visceral pain and vasculature
What is the capacity of the stomach dependent on?
How much you eat
Where is the fundus of the stomach?
At the top, near the cardiac sphincter
Where is the antrum of the stomach?
At the bottom, near the pyloric sphincter
What is the cardiac region of the stomach?
The bit that’s closest to the heart
Where does the stomach end?
Pylorus
What are rugae?
Longitudinal folds of mucosa running all the way down the stomach
Why are rugae necessary in the stomach?
Epithelia don’t have the capacity to stretch/ expand
What happens to the rugae when food fills the stomach?
They flatten out
What are the qualities of the pyloric sphincter?
Big, strong and palpable
Where is the pyloric sphincter?
Trans-pyloric plane
Where is the trans-pyloric plane?
Horizontal line half way between suprasternal notch and pubic symphisis
How many structures lie on the trans-pyloric plane?
12
What structures lie approximately on the trans-pyloric plane?
End of spinal cord L1 of vertebral body Origin of superior mesenteric artery Origin of portal vein Neck of pancreas Pylorus of stomach Second part of duodenum Sphincter of Oddi Hilum of kidneys Duodenojejunal flexure Fundus of gallbladder Tips of 9th costal cartilages
Where is the duodenum?
Retropertioneal
Where pylorus ends
How long is the duodenum?
25cm
What are the different parts of the duodenum?
Superior
Descending
Horizontal
Ascending
What part of the duodenum recieves the common bowel duct and pancreatic duct?
Descending
What part of the duodenum has the duodenojejunal flexure?
Ascending
Where is the pancreas?
Retroperitoneal
Situated in the duodenum’s curvature forming C shape
What does uncinate mean?
Hook like
What are the different parts of the pancreas called?
Uncinate process Head Neck Body Tail
What organ does the spleen point towards?
Spleen
What lies over the abdominal wall?
Skin and two layers of fascia
What muscles make up the anterolateral abdominal wall?
External oblique
Internal oblique
Transversus Abdominis
What direction do the external oblique muscles run in?
Inferiorly and medially
Same direction as external intercostals in thorax
What is the linea alba?
A white line on the front midline
Where does the inguinal ligament run?
Anterior superior iliac spine - Pubic tubercle
When does the external oblique become a tendon?
At the 9th costal cartilage
Where do the internal oblique fibres run?
Superiorly and medially
What is the transversus abdominis adbdominis fibre orientation?
Transverse
What is the most posterior of the anterior wall muscles?
Rectus abdominis
Where does the rectus abdominis run?
Pubic crest - Costal cartilages
What does the rectus abdominis look like from the front?
3 tendinous insertions ; the reason for six packs
What does the rectus abdominis look like from the back?
One muscle
What is a pyramidalis?
A little pyramid between the umbilicus and pubic symphysis on the midline
What is the importance of the pyramidalis?
It does absolutely nothing
What happens to the 3 muscle layers between rib 9 and the anterior superior iliac spine?
They become aponeurotic (tendinous)
What happens to the muscles below the anterior superior iliac spine?
Posterior and rectus sheath (made from the internal oblique and transversus abdominis) run to the front
What is the name given to the region including and below the anterior superior iliac spine?
Arcuate line
Where does the parietal peritoneum attach onto the muscle wall?
Behind all of the muscle (posteriorly)
Why do we need abdominal muscle?
To support the intestines
What is the shape of muscle determined by?
Muscle tone
What is the Quadratus lumborum?
A back abdominal muscle
What does omentum mean?
Apron
What is mesentary?
Double layer of peritoneum which links visceral to parietal peritoneum
What is the name for parietal peritoneum which folds in on itself to become visceral?
Peritoneal fold/ reflection
Where is the ileum?
Distal 3/5 of the small intestine; Hypogastric and right inguinal region
What are the physical properties of the ileum?
In comparison to jejunum: Thinner wall Smaller calibre More Peyer's patches Short vasa recta More arterial arcades
What are the physical properties of the jejunum?
In comparison to ileum:
Thicker wall
Bigger blood vessels- more vascular
Long vasa recta
Where is the jejunum?
Umbilical towards the left iliac fossa
What is absorbed in the ileum?
B12, H2O and electrolytes
What is Merkel’s diverticulum?
An outpouching
What is absorbed in the large intestine?
H2O, electrolytes and drugs
How can the large intestine be distinguished from the small intestine?
Has fat hanging off it Has Teniae Coli Has Haustra Is mobile Has distinct flexures
What is the right flexure of the large intestine known as?
Right colic flexure
Hepatic flexure
What is the left flexure of the large intestine known as?
Left colic flexure
Splenic flexure
What is the structure described as ‘a tube within a funnel’ called?
Anal canal
What are the properties of the anal canal?
Circular layer outside
External sphincter and internal sphincter
What is the visceral surface of the liver?
The contact that the liver has with organs inferior to it
What is the coronary ligament?
A fold/ reflection of peritoneum directly beneath the visceral surface of the liver
What is the hepatorenal recess?
The deepest part of the peritoneal cavity when a person is lying down
What is the falciform ligament?
A double layer of peritoneum which closes off to form the ligament of Teres
What is another name for the hepatorenal recess?
Pouch of Morrison
What is the bare area of the liver?
The surface of the liver which is not covered in any peritoneum and is directly in contact with the diaphragm
How can you identify the bare area of the liver?
It will be dull in comparison to the rest of the liver which will look shiny because of the peritoneum
What is the significance of the foramen of Winslow?
It is the passage between the greater and lesser sacs of the peritoneal cavities
What is the foramen of Winslow also known as?
The epiploic foramen
What lies anterior to the foramen of Winslow?
Free border of the hepatoduodenal ligament
How much BLOOD does the hepatic portal vein supply to the liver?
80%
How much OXYGEN does the hepatic portal vein supply to the liver?
20%
How much BLOOD does the hepatic artery supply to the liver?
20%
How much OXYGEN does the hepatic artery supply to the liver?
80%
Where do the hepatic veins drain to?
Inferior vena cava
What is the difference between the anatomical and physiological left lobes?
Anatomical: Left excludes the quadrate and caudate lobes
Physiological: Left includes the quadrate and caudate lobes
Why can you remove segments of liver without complications?
Liver segments are functionally independent
Liver can regrow and retain function
Where is the gallbladder?
Tucks into the right lobe of the liver
What is the relationship between the 9th costal cartilage and the gallbladder?
This means that the gallbladder lies on the trans-pyloric plane
Where is the body of the gallbladder?
On the inferior surface of the liver
Where is the neck of the gallbladder?
Connecting to the cystic duct
Where does the gallbladder receive its blood supply?
The right hepatic artery via the cystic artery
True or false? The spleen is part of the GI tract
False- Not really…
How big is the spleen?
1 X 3 X 5 inches
How heavy is the spleen?
7 ounces
Where is the spleen?
Left hypochondrium
Reticuloendothelial
Posterior to ribs 9-11
What is the arterial supply of the spleen?
Coeliac artery
What does reticuloendothelial mean?
Mononuclear Phagocytic System (MPS) - part of the immune system that consists of the phagocytic cells
What is the embryological origin of the spleen?
Mesoderm
How can you tell the difference between the spleen and liver when both are enlarged?
The spleen is notched
What is the visceral surface of the spleen related to?
Surface of stomach, left colic flexure and kidney
What is the common hepatic artery made from?
Left hepatic + Right hepatic arteries
What is the common bile duct made from?
Common hepatic artery and cystic duct
Where does the common bile duct run?
Posteriorly to the first part of the duodenum
What is the sphincter of Oddi also known as?
Hepatopancreatic sphincter
What generally happens to lymphatics when you block them?
They go backwards
What are clusters of glandular epithelial cells called?
Acini
What constitutes the endocrine portion of the pancreas?
Islets of Langerhans
What is the difference between Langerhan cells and Islets of Langerhans?
Langerhans cells found in skin + mucosa
Islets of Langerhans found in pancreas
What constitutes the exocrine portion of the pancreas?
Acini
What consititutes the reticuloendothelial system?
Spleen, liver, renal tubular cells and macrophages
