You are what you eat Block 3 Week 2 Flashcards
Know the position of the organs in the abdomen ?
- We have the stomach and Infront of it we have the pancreas.
- Wrapped around the pancreas we have the small intestine
- We have the liver and right kidney on the right
- We have the spleen and left kidney on the left
What is the function of the liver ?
- Produces bile - which a compound needed to digest fat and to absorb vitamin A, D, E and K
- Detoxification - Clearing the blood of drugs and other poisonous substances
- Regulation of glycogen storage - Conversion of excess glucose into glycogen for storage (glycogen can later be converted back to glucose for energy) and to balance and make glucose as needed.
- Processing of hemoglobin for use of its iron content (the liver stores iron)
- Production of cholesterol and special proteins to help carry fats through the body
- Clearance of bilirubin, also from red blood cells. If there is an accumulation of bilirubin, the skin and eyes turn yellow.
- Conversion of poisonous ammonia to urea (urea is an end product of protein metabolism and is excreted in the urine)
Where is the liver found ?
- Right upper quadrant then projecting into the left upper quadrant
- Gallbladder in the right upper quadrant
Liver in a cadaver
In between the 2 big lobes of the liver we have the falciform ligament
Describe the liver surfaces ?
- Diaphragmatic surface (red)
- Visceral surface (blue)
Extra info:
- kidney is retroperitoneal
Describe the peritoneum ?
- The peritoneum is a continuous membrane which lines the abdominal cavity and covers the abdominal organs and and provides pathways for blood vessels and lymph to travel to and from the viscera.
- The peritoneum consists of two layers the parietal and visceral peritoneum.
- Both layers of the peritoneum are made up of simple squamous epithelial cells called mesothelium.
- Parietal perineum: lines the internal surface of the abdominopelvic wall
- Visceral peritoneum cover the abdominal viscera ( organs)
Where is parietal peritoneum derived from ?
Somatic mesoderm in the embryo
Where is the visceral peritoneum derived from ?
Splanchnic mesoderm in the embryo
What is intraperitoneal (aka peritoneal) ?
- Are organs involved by visceral peritoneum, which covers the organ both anteriorly and posteriorly.
Examples:
- Stomach
- Liver
- Spleen
What are retroperitoneal organs ?
- Retroperitoneal organs are not associated with visceral peritoneum
- they are only covered in PARIETAL peritoneum, and that peritoneum only covers their ANTERIOR surface.
Where is bile made and stored ?
Bile is a fluid that is made and released by the liver and stored in the gallbladder
Why does blood go from the stomach and small intestine to the liver ?
All the blood leaving the stomach and intestines passes through the liver. The liver processes this blood and breaks down, balances, and creates the nutrients
and also metabolizes drugs into forms that are easier to use for the rest of the body or that are nontoxic.
Describe the livers dual blood supply ?
There are 2 distinct sources that supply blood to the liver, including the following:
- Oxygenated blood flows in from the hepatic artery
- Nutrient-rich blood flows in from the hepatic portal vein
Describe the structure of the liver ?
Structure: 4 anatomical lobes (right, left, caudate, quadrate) 8 functional segments
How much fat do we take in the western diet ?
100-150g daily. This contributes to about 40% of out total dietary energy intake.
Fat and water do not mix.
Fat always has to be in solution
- If we put oil and water into a bottle it will separate into 2 different spaces. So oil at the top and water at the bottom.
- If we shake the bottle the oil and water will mix which is called emulsification. The fat is broken down into smaller droplets.
- TAG has to be digested in an aqueous environment which is the intestine.
- Bile and enzymes are released into the small intestine which help with the breakdown of fats.
What prevents the small TAG particles from re-aggregating
into a bulk fat phase in the duodenum where mixing is not
so active?
Bile is produced in the liver
Stored in the gallbladder
Released into the small intestine
The bile covers the fats in a polar surface which prevents small emulsion droplets from reaggregating
Where does fat wee ingest come from ?
Triacylglycerol’s from:
- cooking oils
- butter
- margarine
- meat fat
- cereal
- nut oil
Phospholipids from cell membranes
Cholesterol esters from animal cell fat stores
Cholesterol from animal cell membranes
What are also taken in when we take in fats ?
- Vitamins
- essential fatty acids
What are the basics of fat digestion ?
Lipids are digested mainly in the small intestine by bile salts through the process of emulsification.
Bile salts help break down big lipid droplets into smaller droplets
This makes it easier for lipase enzymes to digest the Triacyglycerides.
Another factor that helps is colipase and amphipathic protein that binds and anchors lipase at the surface of the emulsion droplet
Bile salts solubilize the products of lipase digestion into micelles to facilitate the uptake into enterocytes in the jejunum region
What are the basics of fat digestion ?
Lipids are digested mainly in the small intestine by bile salts through the process of emulsification.
Bile salts help break down big lipid droplets into smaller droplets
This makes it easier for lipase enzymes to digest the Triacyglycerides
Bile salts solubilize the products of lipase digestion into micelles to facilitate the uptake into enterocytes in the jejunum region
How are fats absorbed ?
- After digestion, monoglycerides and fatty acids associate with bile salts and phospholipids to form micelles. Micelles are about 200 times smaller than emulsion droplets. Micelles are necessary because they transport the poorly soluble monoglycerides and fatty acids to the surface of the enterocyte where they can be absorbed. As well, micelles contain fat soluble vitamins (A, D, E and K) and cholesterol.
- Micelles are constantly breaking down and reforming, feeding a small pool of monoglycerides and fatty acids that are in solution. The hydrophilic outer region of the micelles enables it to enter the aqueous layer surrounding the microvilli that form the brush border of the enterocytes. Only freely dissolved monoglycerides and fatty acids can be absorbed, not the micelles. Because of their nonpolar nature, monoglycerides and fatty acids can just passively diffuse across the plasma membrane of the enterocyte. The bile salt portion of the micelle remains within the lumen of the gut until the terminal ileum. Some absorption may be facilitated by specific transport proteins.
- Once inside the enterocyte, in the smooth endoplasmic reticulum monoglycerides and fatty acids are resynthesized into TAG. The TAG is packaged, along with cholesterol and fat soluble vitamins, into chylomicrons. Chylomicrons are lipoproteins, special particles that are designed for the transport of lipids in the circulation.
- Chylomicrons are released by exocytosis at the basolateral surface of the enterocytes. Because they are particles, they are too large to enter typical capillaries. Instead they enter lacteals of the lymph and leave the intestine in the lymph.
- Chylomicrons are then released into venous circulation via the thoracic duct.
- Lipids thus avoid the hepatic portal vein and bypass the liver in the short term.
What are the sources of lipid - degrading enzymes ?
3 types:
- Lingual lipase from Ebner’s glands on the dorsal surface of the tongue
- Gastric lipase
- Pancreatic lipase: which include pancreatic lipase, phospholipase and cholesterol esterase’s
In which part of the small intestine are fats absorbed the most ?
Jejunum
Which lipid products can diffuse freely into enterocytes ?
- Monoglycerides
- Free fatty acids
- Cholesterol
- Fat soluble vitamins
- Lecithin
How much fat is found in feces ?
- The feces contains about 5% fat most of which is derived from bacteria
- Increased amounts of fat are found in the feces if bile production is diminished or if bile is prevented from entering the duodenum.
Why can pancreatitis cause greasy diarrhea bowel movements ?
What are the two primary bile acids ?
2 Primary bile acids made by the liver:
- Cholic acid
- Chenodeoxycholic acid
Bile acids are derived from the metabolism of cholesterol.
Cholic acid and chenodeoxycholic acid are formed in the HEPATOCTYES themselves and are known as primary bile acids.
In the intestine, the secondary bile acids, deoxycholic acid and lithocholic acid are formed in small amounts from the primary acids by the dehydroxylating action of bacteria.
Describe the production of bile ?
- Bile is produced by HEPATOCYTES.
- Hepatocytes secrete a fluid known as hepatic bile into bile canaliculi.
- This is a isotonic fluid with a pH between 7 and 8.
- This bile contains bile salts, bile pigments , cholesterol, lecithin and mucus.
- As it passes along the bile ducts, the ductal epithelial cells modify this primary secretion by secreting watery bicarbonate rich fluid. This adds a lot of volume to the bile.
- Overall the liver produces 500-1000ml of bile a day. The bile may be continuously discharged into the duodenum or stored in the gallbladder, during which time its composition changes (more on this).
How are bile salts which are present in bile produced ?
- The primary bile acids are conjugated ( by means of peptide linkage ) to amino acids such as GLYCINE and TAURINE in a complex with sodium ], to form water - soluble bile salts.
Describe bile salts and then micelles ?
-Bile salts Amphipathic.
This means they have both hydrophobic and hydrophilic regions.
- The bile salts form aggregates called micelles when they reach a certain concentration in the bile. This is known as critical micellar concentration.
- The micelles are organized so the hydrophilic groups of the bile salts face the aqueous medium while the hydrophobic groups face each other to form a core.
What is the function of CCK (Cholecystokinin) ?
Enterohepatic: relating to or denoting the circulation of bile salts and other secretions from the liver to the intestine, where they are reabsorbed into the blood and returned to the liver.
- CCK is released from duodenal mucosa
- CCK stimulates the gallbladder to release bile by contraction of the gallbladder and relaxion of the sphincter of oddi
Bile acids are recycled. What is the journey on how their recycled called?
Enterohepatic circulation
- About 94% of bile acids that enter the intestine in the bile are recycled.
- The are reabsorbed into portal circulation by active transport form the DISTAL ILEUM.
- Many of the bile salts return to the liver unaltered and are recycled. Some are deconjugated in the gut lumen and returned to the liver for reconjugation and recycling.
- A small number are deconjugated and modified by intestinal bacteria to secondary bile acids such as lithocholic acid.
- Lithocholic acid is insoluble and excreted into feces. It is estimated bile salts can be recycled 20 times before being recycled.
Describe the structure of chylomicrons, very low density lipoproteins, low density lipoproteins ?
What are the differences between different Omegas ?
What are the differences between omega- 3 and omega-6 fatty acids?
What is the major route for the excretion of cholesterol from the body ?
- Bile is the major route for the excretion of cholesterol from the body.
- Cholesterol is secreted into bile as micelles. It is present in the hydrophobic core of the micelle.
- If excess cholesterol is present and cannot be solubilized into micelles, it may form crystals in the bile.
- This may contribute to the formation of cholesterol gallstones in the hepatic ducts or gallbladder, by acting as a nuclei for the deposition of calcium and phosphate.
- If the common bile duct becomes blocked bile cannot enter the duodenum. There is a distension and a build up of pressure within the gallbladder which can result in severe pain ( biliary colic) and jaundice
What are bile pigments ?
- They are formed from the breakdown of old red blood cells in the spleen. The excretory products of heme ( porphyrins).
- They are responsible for the characteristic colors of bile and feces.
- The major bile pigment is Bilirubin
- In the liver bilirubin is conjugated with glucuronic acid.
- In the intestine bilirubin is hydrolyzed by bacteria to form Urobilinogen.
- Some urobilinogen is excreted which gives feces its brown color. Some is excreted in urine
- Some bilirubin is reabsorbed from the intestine into the blood. And is resecreted into bile in the liver
What is Jaundice ?
Jaundice is due to abnormal levels of bilirubin in the blood ( hyperbilirubinemia).
- It is characterized by yellow discoloration of the skin, sclera of the eyes, and deep tissues.
What are some of the causes of Jaundice ?
- Excessive hemolysis of red blood cells
- Impaired uptake of bilirubin by hepatocytes
- Obstruction of bile flow either through the bile caniculi or the bile ducts
- Excessive hemolysis may occur following a poorly matched blood transfusion or in certain heritadory disorders.
- Jaundice is also seen in newborns whose fetal red cells are hemolyzing more quickly than the immature liver can process the bilirubin.
Some of the symptoms of jaundice ?
- Feces are pale due to the absence of bilirubin and often contain fatty streaks due to the lowered absorption of dietary fat.
- The urine is normally darker, due to the increased excretion of bilirubin via the kidneys.
What is the purpose of the abdominal wall ?
- Forms a firm, yet flexible boundary which keeps the abdominal viscera in the abdominal cavity and assists the viscera in maintaining their anatomical position against gravity.
-Protects the abdominal viscera from injury.
- Assists in forceful expiration by pushing the abdominal viscera upwards.
- Is involved in any action (coughing, vomiting, defecation) that increases intra-abdominal pressure.
Describe the anterolateral abdominal wall ?
Anterolateral means anterior and lateral
The anterolateral abdominal wall consists of four main layers (external to internal):
-skin
- superficial fascia
- muscles and associated fascia
- parietal peritoneum
Describe the superficial fascia ?
- The superficial fascia is connective tissue
The composition of this layer depends on its location:
Above the umbilicus – a single sheet of connective tissue. It is continuous with the superficial fascia in other regions of the body.
Below the umbilicus – divided into two layers; the fatty superficial layer (Camper’s fascia) and the membranous deep layer (Scarpa’s fascia).
The superficial vessels and nerves run between these two layers of fascia.
Describe the muscles of the abdominal wall ? ( anterolateral abdominal wall)
The muscles of the anterolateral abdominal wall can be divided into two main groups:
- Flat muscles – three flat muscles, situated laterally on either side of the abdomen.
- External Oblique
- Internal oblique
- Transversus Abdominis
- Vertical muscles – two vertical muscles, situated near the mid-line of the body.
- Rectus Abdominis
- Pyramidalis
Describe the external oblique muscle of the anterolateral abdominal wall ?
The external oblique is the largest and most superficial flat muscle in the abdominal wall. Its fibres run inferomedially.
Attachments: Originates from ribs 5-12, and inserts into the iliac crest and pubic tubercle.
Functions: Contralateral rotation of the torso.
Innervation: Thoracoabdominal nerves (T7-T11) and subcostal nerve (T12).
Describe the internal oblique muscle of the anterolateral abdominal wall ?
The internal oblique lies deep to the external oblique. It is smaller and thinner in structure, with its fibres running superomedially (perpendicular to the fibres of the external oblique).
Attachments: Originates from the inguinal ligament, iliac crest and lumbodorsal fascia, and inserts into ribs 10-12.
Functions: Bilateral contraction compresses the abdomen, while unilateral contraction ipsilaterally rotates the torso.
Innervation: Thoracoabdominal nerves (T7-T11), subcostal nerve (T12) and branches of the lumbar plexus.
Describe the Transversus Abdominis muscle of the anterolateral abdominal wall ?
The transversus abdominis is the deepest of the flat muscles, with transversely running fibres. Deep to this muscle is a well-formed layer of fascia, known as the transversalis fascia.
Attachments: Originates from the inguinal ligament, costal cartilages 7-12, the iliac crest and thoracolumbar fascia. Inserts into the conjoint tendon, xiphoid process, linea alba and the pubic crest.
Functions: Compression of abdominal contents.
Innervation: Thoracoabdominal nerves (T7-T11), subcostal nerve (T12) and branches of the lumbar plexus.
Describe the Rectus Abdominis of the anterolateral abdominal wall ?
The rectus abdominis is long, paired muscle, found either side of the midline in the abdominal wall. It is split into two by the linea alba. The lateral borders of the muscles create a surface marking known as the linea semilunaris.
At several places, the muscle is intersected by fibrous strips, known as tendinous intersections. The tendinous intersections and the linea alba give rise to the ‘six pack’ seen in individuals with a well-developed rectus abdominis.
Attachments: Originates from the crest of the pubis, before inserting into the xiphoid process of the sternum and the costal cartilage of ribs 5-7.
Functions: As well as assisting the flat muscles in compressing the abdominal viscera, the rectus abdominis also stabilises the pelvis during walking, and depresses the ribs.
Innervation: Thoracoabdominal nerves (T7-T11).
What is the inguinal canal ?
The inguinal canal is a short passage that extends inferiorly and medially through the inferior part of the abdominal wall. It is superior and parallel to the inguinal ligament.
- The canal serves as a pathway by which structures can pass from the abdominal wall to the external genitalia.
- It is of clinical importance as a potential weakness in the abdominal wall, and thus a common site of herniation.
What is Inguinal hernia ?
- Inguinal hernia is the most common type of hernia
An inguinal hernia occurs when tissue, such as part of the intestine, protrudes through a weak spot in the abdominal muscles. The resulting bulge can be painful, especially when you cough, bend over or lift a heavy object. However, many hernias do not cause pain.
An inguinal hernia isn’t necessarily dangerous. It doesn’t improve on its own, however, and can lead to life-threatening complications. Your doctor is likely to recommend surgery to fix an inguinal hernia that’s painful or enlarging. Inguinal hernia repair is a common surgical procedure.
Describe the borders of the inguinal canal ?
-The floor: inguinal ligament and thickened medially by the lacunar ligament
-The anterior wall: aponeurosis of external oblique, and internal oblique laterally
-The roof: transversalis fascia, internal oblique and transversus abdominis
-The posterior wall: transversalis fascia
The inguinal canal on a cadaver ?
What is the mesentery ?
- The mesentery is a double fold of peritoneal tissue that suspends the small intestine and large intestine from the posterior abdominal wall.
- The superior and inferior mesenteric arteries arise from the ABDOMINAL AORTA and travel in the mesentery to supply the abdominal viscera. These vessels also give rise to branches that supply the mesentery itself.
Superior mesenteric artery – supplies the organs of the midgut – from the major duodenal papilla to the proximal two thirds of the transverse colon.
Inferior mesenteric artery – supplies the organs of the hindgut – the distal one third of the transverse colon, splenic flexure, descending colon, sigmoid colon and rectum.
The venous drainage of the mesentery is via the superior mesenteric vein (SMV) and inferior mesenteric vein (IMV), which both run alongside their associated arteries.
Where does the superior mesenteric artery supply blood to ?
Where does the inferior mesenteric artery supply blood to ?
Superior mesenteric artery – supplies the organs of the midgut – from the major duodenal papilla to the proximal two thirds of the transverse colon.
The superior mesentric artery arises at L1
Inferior mesenteric artery – supplies the organs of the hindgut – the distal one third of the transverse colon, splenic flexure, descending colon, sigmoid colon and rectum.
The venous drainage of the mesentery is via the superior mesenteric vein (SMV) and inferior mesenteric vein (IMV), which both run alongside their associated arteries.
Similarly, the sympathetic inputs to the foregut, midgut and hindgut arise from the thoracic and lumbar splanchnic nerves, i.e. T5-T9, T9-T12 and L1-L2 respectively. The parasympathetic innervation to the foregut and midgut is supplied by the vagus nerve (cranial nerve 10) while the pelvic splanchnic nerves provide parasympathetic innervation to the hindgut.
MRI is an acronym to remember the branches off the SMA to the large intestine:
- Middle Colic
- Right Colic
- Ileocolic artery
Describe the small intestine ?
Small intestine:
- Duodenum
- Jejunum
- Ileum
What is the Omentum ?
- Omentum are sheets of visceral peritoneum that extend from the stomach and proximal part of the duodenum to other organs.
There are 2 omentums:
- greater omentum
- lesser omentum
Greater omentum:
- descends from the greater curvature of the stomach then folds back up and attaches to the anterior surface of the transverse colon.
Lesser Omentum:
- considerably smaller than the greater and attaches to the lesser curvature of the stomach to the liver.
It consists of two parts: the hepatogastric ligament (the flat, broad sheet) and the hepatoduodenal ligament (the free edge, containing the portal triad).
What is a peritoneal ligament ?
A peritoneal ligament is a double fold of peritoneum that connects viscera together or connects viscera to the abdominal wall.
An example is the hepatogastric ligament, a portion of the lesser omentum, which connects the liver to the stomach.
Know the structures of the posterior abdominal wall ?
- Iliacus
- Quadratus lumborum
- Psoas major
What is the histology of the small intestine ?
Simple columnar epithelium (just like the stomach)
Describe the jejunum ?
Describe the ileum ?
- The jejunum begins at the duodenojejunal flexure.
- There is no clear external distinguishing point between the jejunum and ileum – although the two parts are macroscopically different.
- The ileum ends at the ileocaecal junction.
- Not a lot of absorption happens in the duodenum. The majority of absorption of absorption does take place at the jejunum. Less absorption takes place in the ileum.
What are vasa recta ?
Vasa racta : Vasa recta are straight capillaries coming off from arcades in the mesentery of the jejunum and ileum, and heading toward the intestines.
Jejunum vasa racta : long
Ileum vasa racta : Short
Artertial Arcades:
Jejunum : 1-2 rows
Ileum : 4-5 rows
Difference between jejunum and ileum ?
What is Meckel’s diverticulum ?
Meckel’s diverticulum, - a slight bulge in the small intestine present at birth and a vestigial remnant of the vitelline duct
- It occurs in 2% of the population
- normally disappears at 6 weeks gestation but remains in 2% of the population
Describe the structure of the large intestine ?
- Caecum
- Ascending colon
- Transverse colon
- Descending colon
- Sigmoid colon
- In the large intestine more water absorption takes place. Electrolytes and drugs are also absorbed. Remember absorption of water also takes place in the jejunum and ileum.
- There is also bacteria here. Good bacteria is being used to break down tissue.
- We also get rid of waste products here
Describe the blood supply to the large intestine ?
The ascending colon receives arterial supply from two branches of the superior mesenteric artery:
- the ileocolic
- right colic arteries.
The ileocolic artery gives rise to colic, anterior cecal and posterior cecal branches – all of which supply the ascending colon.
The transverse colon is supplied by branches of the superior mesenteric artery and inferior mesenteric artery:
- Right colic artery (from the superior mesenteric artery)
- Middle colic artery (from the superior mesenteric artery)
- Left colic artery (from the inferior mesenteric artery)
The descending colon is supplied by:
- single branch of the inferior mesenteric artery; the left colic artery.
Sigmoid colon:
- The sigmoid colon receives arterial supply via the sigmoid arteries (branches of the inferior mesenteric artery).
Branches off IMA:
the left colic artery, sigmoid artery and superior rectal artery.
- IMA arises at L3
Some parts of the large intestine are peritoneal and other parts are retroperitoneal
Intraperitoneal (peritoneal):
- Appendix
- Caecum
- Transverse colon
- Appendix
Retroperitoneal:
- Ascending colon
- Descending colon
What are omental appendices ?
Attached to the surface of the large intestine are omental appendices – small pouches of peritoneum, filled with fat.
- It is specifically the appendix, transverse colon and sigmoid colon which have these appendices.
- Running longitudinally along the surface of the large bowel are three strips of muscle, known as the teniae coli. They are called the mesocolic, free and omental coli.
- The teniae coli contract to shorten the wall of the bowel, producing sacculations known as haustra.
The large intestine has a much wider diameter compared to the small intestine.
What are the longitudinal strands running along the surface of the large intestine ?
- Running longitudinally along the surface of the large bowel are three strips of muscle, known as the teniae coli. They are muscular strands which contract to move the fecal matter along the large intestine.
- Individually they are called mesocolic, free and omental coli
- We also have Haustra which are the bulges. They help to give shape to the large intestine.
- There are also deposits of fat around the large intestine which are called the Appendices epiploicae. They are key distinguishing characteristics of the large intestine to help us tell the small and large intestine apart.
How do we tell the difference between the large and small intestine ?
Right image:
- we can see the bulges (haustra)
- We can see fatty deposits (Appendices epiploicae)
- At the end we can see a muscular tube which is the tenia coli
so the right image is the large intestine.
Left image:
- We can see fatty deposits
- we cannot see haustra
- we cannot see tenia coli
So this is the large intestine.
Describe the Caecum of the small intestine?
- Chyme is passed from the ileum to the caecum
- If we look inside the ileum we can see the ileocecal valve.
- Attached to the end of the ceacum is the appendix. It is supported by the mesoappendix, a fold of mesentery which suspends the appendix from the terminal ileum.
- The exact function of the appendix is unknown. It could have a role for monitoring bacterial levels. We know it can be removed without having major side effects.
What is Appendicectomy ?
An appendectomy, also termed appendicectomy, is a surgical operation in which the vermiform appendix is removed. Appendectomy is normally performed as an urgent or emergency procedure to treat complicated acute appendicitis.
What happens in the large intestine ?
- Fecal matter is pushed up along the ascending colon, transverse colon, descending colon.
- Water is reabsorbed as you go along the colon.
- This continues until we get to the rectum .
Describe the rectum?
- The rectum ends at the anorectal junction
- Its found at S3
- It has no appendices, haustrations
-It does have tenia coli. Infact the tenia coli expands over the rectum
- It has transverse rectal folds that feces can sit on top of.
- The first 2/3 of the rectum has peritoneum but the last 1/3 doesn’t have any.
- Now you have the feces in the rectum it has to pass through the anal canal.
Describe the anal canal ?
Has 2 sphincters:
- internal anal sphincter
- external anal sphincter
- Above the pectinate line the histology is simple columnar epithelium and the embryological origin is the endoderm.
- below the pectinate line (4cm long) we have non -keratinized stratified squamous epithelium and the embryological origin is ectoderm.
- below the anocutaneous line the histology changes once again to keratinized stratified squamous epithelium.
Describe the blood supply to the rectum and anal canal ?
Above pectinate line:
- The rectum and and anal canal are supplied by the superior rectal artery and superior rectal vein.
- nerve: hypogastric plexus
Below pectinate line:
- The anal canal is supplied by the inferior rectal artery and inferior rectal vein.
- nerve: inferior rectal nerves
What are Hemorrhoids ?
- Hemorrhoids are swollen veins in your anus and lower rectum, similar to varicose veins
- Piles (haemorrhoids) are lumps inside and around your bottom (anus).
- Symptoms of piles include bright red blood after you poo, an itchy anus, and slimy mucus coming from your bottom.
Piles usually get better on their own. You can ease discomfort by avoiding constipation. You may need hospital treatment if your piles are severe.
Describe the autonomic nerve (involuntary) supply and the somatic nerve supply (voluntary) to the rectum and anal canal?
The smooth muscles of the rectum and anal canal are supplied by parasympathetic and sympathetic nerves.
- parasympathetic nerves: S2, S3 and S4 ( pelvic splanchnic nerve)
- sympathetic nerves: T11 - L2 (inferior hypogastric plexus)
- visceral sensory fibers follow the parasympathetic supply.
The external anal sphincter:
- somatic motor sensory: pudendal nerve
Describe the process of defecation ?
- Feces stretch the rectum and stimulate stretch receptors, which transmit signals to the spinal cord.
- A spinal reflex stimulates contraction of the rectum
- The spinal reflex also relaxes the internal anal sphincter
- Impulses from the brain prevent untimely defecation by keeping the eternal anal sphincter contracted. Defecation occurs only if this sphincter relaxes.
- We need voluntary relaxation of the external sphincter for defection tot occur.
Describe the ligaments of the liver ?
There are a number of ligaments that attach to the liver. They are formed by the double layer of peritoneum.
- Falciform ligament: – this sickle-shaped ligament attaches the anterior surface of the liver to the anterior abdominal wall. Its free edge contains the ligamentum teres, a remnant of the umbilical vein.
- Coronary ligament (anterior and posterior folds) : attaches the superior surface of the liver to the inferior surface of the diaphragm and demarcates the bare area of the liver The anterior and posterior folds unite to form the triangular ligaments on the right and left lobes of the liver.
- Triangular ligaments (left and right):
The left triangular ligament is formed by the union of the anterior and posterior layers of the coronary ligament at the apex of the liver and attaches the left lobe of the liver to the diaphragm.
The right triangular ligament is formed in a similar fashion adjacent to the bare area and attaches the right lobe of the liver to the diaphragm.
Lesser omentum – Attaches the liver to the lesser curvature of the stomach and first part of the duodenum. It consists of the hepatoduodenal ligament (extends from the duodenum to the liver) and the hepatogastric ligament (extends from the stomach to the liver). The hepatoduodenal ligament surrounds the portal triad.
Describe Hepatic Recesses ?
The hepatic recesses are anatomical spaces between the liver and surrounding structures. They are of clinical importance as infection may collect in these areas, forming an abscess.
Subphrenic spaces – located between the diaphragm and the anterior and superior aspects of the liver. They are divided into a right and left by the falciform ligament.
Subhepatic space – a subdivision of the supracolic compartment (above the transverse mesocolon), this peritoneal space is located between the inferior surface of the liver and the transverse colon.
Morison’s pouch – a potential space between the visceral surface of the liver and the right kidney. This is the deepest part of the peritoneal cavity when supine (lying flat), therefore pathological abdominal fluid such as blood or ascites is most likely to collect in this region in a bedridden patient.
Describe the structure of the liver ?
Glisson’s capsule: The liver is covered by a fibrous layer, known as Glisson’s capsule. It is comprised of a large right lobe and smaller left lobe.
There are two further ‘accessory‘ lobes that arise from the right lobe, which are located on the visceral surface of liver:
- Caudate lobe – located on the upper aspect of the visceral surface. It lies between the inferior vena cava and a fossa produced by the ligamentum venosum (a remnant of the fetal ductus venosus).
- Quadrate lobe – located on the lower aspect of the visceral surface. It lies between the gallbladder and a fossa produced by the ligamentum teres (a remnant of the fetal umbilical vein).
Separating the caudate and quadrate lobes is a deep, transverse fissure – known as the porta hepatis. It transmits all the vessels, nerves and ducts entering or leaving the liver with the exception of the hepatic veins.
Describe the blood supply to the liver ?
The liver has a unique dual blood supply:
Hepatic artery proper (25%) – supplies the non-parenchymal structures of the liver with arterial blood. It is derived from the coeliac trunk.
The hepatic artery proper branches into the left hepatic, right hepatic and middle hepatic artery.
Hepatic portal vein (75%) – supplies the liver with partially deoxygenated blood, carrying nutrients absorbed from the small intestine. This is the dominant blood supply to the liver parenchyma, and allows the liver to perform its gut-related functions, such as detoxification.
Venous drainage of the liver is achieved through hepatic veins. The central veins of the hepatic lobule form collecting veins which then combine to form multiple hepatic veins. These hepatic veins then open into the inferior vena cava.
- The inferior mesenteric vein drains into the splenic vein, which then drains into the portal vein.
- The superior mesenteric vein drains straight into the hepatic portal vein.
What are the branches of the coeliac trunk ?
- Splenic artery
- Common hepatic artery
- Left gastric artery
How does the blood go from the liver to the circulatory system ?
This blood leaves through the hepatic veins and drains into the through the inferior vena cava.
The hepatic veins are:
- the right hepatic vein
- left hepatic vein
- middle hepatic vein
They all drain into the inferior vena cava.
Describe the falciform ligament of the liver ?
- The falciform ligament helps the liver attach to the diaphragm and anterior abdominal wall.
- As it goes up it splits into the coronary ligament which cover parts of the left and right lobe.
- Round ligament (ligamentum teres) comes off the inferior end of the falciform ligament.
Where is the gall bladder positioned ?
- Fundus of the gallbladder lies at the 9th costal cartilage
- L1
What are the extensions of the coronary ligaments on the posterior surface called ?
Triangular ligaments (left and right):
The left triangular ligament is formed by the union of the anterior and posterior layers of the coronary ligament at the apex of the liver and attaches the left lobe of the liver to the
diaphragm.
The right triangular ligament is formed in a similar fashion adjacent to the bare area and attaches the right lobe of the liver to the diaphragm.
The inferior vena cava runs behind the liver upwards
Surrounding organs leave impressions on the liver
Gastric
Duodenal
Renal
Colic (right colic flexure)
Other structures on the posterior surface of the liver ?
- Gall bladder
- Cystic duct
- Hepatic duct (common hepatic duct)
- Bile duct
What is the fissure for ligamentum teres a remanant of ?
What is the fissure for ligamentum venosum a remanent of ?
Ductus Venosus becomes the fissure for ligamentum venosum
Umbilical Vein becomes the fissure for ligamentum teres
Caudate and quadrate lobe
caudate is at top because it comes first in the alphabet
Describe the porta hepatis (portal triad) of the liver ?
The follow structures enter from the hepatic portal vein ?
- The hepatic portal vein
- the hepatic artery
- bile duct (exits through the porta hepatis)
- plus nerves and lymphatics
Acronym to remember what is anterior to posterior:
DAV - duct artery vein
What supplies the blood supply to the gallbladder ?
Cystic artery
It branches of the right hepatic artery
The structures entering and exiting the portal triad (hepatis) on a cadaver ?
What are the pelvic splanchnic nerves ?
Where do the pelvic splanchnic nerves supply?
The principal function of the pelvic splanchnic nerves is to provide the preganglionic parasympathetic nerve fibers to supply the hindgut and pelvic viscera
The pelvic splanchnic nerves, also known as nervi erigentes, are preganglionic (presynaptic) parasympathetic nerve fibres that arise from the S2, S3 and S4 nerve roots of the sacral plexus
Auditory tube (Eustachian tube) ?
- Communication between nose and middle ear occurs through here
Uvula ?
- nasopharynx ends at the uvula
- The oropharynx ends at the epiglottis
Epiglottis
Epiglottis
Stomach
-Cardiac region
-Fundus
- greater curvature
- lesser curvature
Duodenum, Pancreas, Spleen
Coeliac plexus ?
Coeliac plexus branches:
- Splenic artery
- Left gastric artery
- hepatic artery
The left gastric artery has been cut off for this image
Right gastric
- The right gastric branches off the hepatic artery and supplies blood to the lesser curvature of the stomach.
Short gastric
- Short gastric artery is a branch off the splenic artery and it supplies the lesser curvature of the stomach
Oesphagus, Fundus, Stomach
Greater curvature, Lesser curvature
Duodenum and Pancreas
Splenic artery runs over the spleen
Liver and Spleen
- The left lobe of the liver has been removed
Campers and Scarpa’s fascia
- Campers fascia is fatty soft tissue
- Scarpa’s fascia is more tough and fibrous and is the tissue we are more familiar with on cadavers
External oblique, Internal oblique, Transversus abdominus
Rectus Abdominis muscle
Arcuate line ?
- The arcuate line of rectus sheath, the linea semicircularis, the arcuate line, or the semicircular line of Douglas, is a horizontal line that demarcates the lower limit of the posterior layer of the rectus sheath. It is commonly known simply as the arcuate line.
- The point where we are going from the rectus sheath to muscle is known as the arcuate line
Inferior gastric artery
- Inferior gastric artery lies deep to the arcuate line
