Anatomy Flashcards
What is x-ray absorption dependant on?
i. Thickness of tissue
ii. Density of tissue (mass per unit volume)
iii. Atomic number of tissue (to the 4th power) = STRONGEST INFLUENCE: H = 1, C = 6, O = 8, Ca = 20
What does it mean if something is more black on an x-ray?
If something is more black it is more lucent or less opaque (backer)
What is the order of lucency of components of the body?
Air -> fat -> soft tissues, muscle, liver, fluid -> bone
How do we improve the natural differences in x-ray absorption?
Contrast medium
Barium meal
Barium enema
Endoscopic retrograde cholangiopancreatography (ERCP)
Percutaneous transhepatic cholangiograph
Inject radio-opaque material into vessels
What is barium meal?
patient ingests barium (atomic number 56) -> moves through the GIT and allows visualization of the GIT i. Visualize esophagus and stomach almost instantly 1. Commonly endoscopy/gastroscopy is used instead ii. To visualize small bowel drink higher volume and take X-rays over a period of hours (1 hour) 1. Commonly used as small bowel hard to reach with endoscopy
What is a barium enema?
contrast into rectal tube under gravity allows visualization of the large intestine (must clean colon beforehand) i. NB. colonoscopy largely replaced this examination
What is the Endoscopic retrograde cholangiopancreatography (ERCP)
canulate the ampulla of the pancreas and introduce contrast which runs into the bile duct or pancreatic duct
What is Percutaneous transhepatic cholangiography?
Inject thin needle with contrast into the liver allowing visualization of the bile ducts
How do we visualise vessels under x-ray?
Intravscular contrast medium injected either intravenously or intra-arterialy.
Commonly organic salts containing iodine
The contrast medium then distributes through the blood vessels (sometimes extravascular as well). This is then visualised by taking a series of x-rays in quick succession
What is a celiac angiogram?
- Catheter -> select branch of aorta -> 50-20ml of contrast injected and images rapidly taken 2. See it moving through small arteries, capillaries then veins
What is indirect protography?
Catheter-> splenic artery -> 20 seconds -> dense blush -> contrast is opacifying the blood through the splenic vein and as a result of that the portal vein can be visualized
What is an intravenous contrast with biliary excretion?
Molecule transported by hepatocytes complexed to contrast agent which contains iodine -> visualization of the bile ducts
How does a CT scan work?
Ring of X-ray detectors with a moving X-ray tube and the patient is also moving
10-15 seconds to do the entire chest and abdomen (one breath hold)
What is the unit of measurement in a CT scan. What is an area referred to as in a CT scan?
Housenfield unit (greyscale) Voxel - pixel with depth
What is radio-isotope imaging?
Radioisotopes (most common is Tc-99m, good energy short half-life) i. Attach to particular molecules (targets certain tissues) -> introduce to body (usually intravenous) ii. Emit gamma rays -> recorded by “gamma camera”
What is radioisotope biliary imaging?
Radioisotope attached to molecule which behaves like bilirubin ii. Taken up by hepatocytes and excreted iii. Isotopes show up as black (hot areas)
What are the advantages and disadvantages of radioisotope imaging?
Advantage = functional, physiological Downside = poor anatomical resolution
What imaging techniques use ionizing radiation?
Why should it be avoided?
X-ray
CT
PET
Ionizing radiation can be harmful
How does ultrasound worK
Produces thin sectional imaging using echoes returned from tissue interfaces
What is dopler ultrasound?
Doppler effect describes a perceived change in frequency of waves when there is relative movement between source of the wave and observer of the wave
ii. In this case source of sound is the RBC; generate weak echoes but it is strong enough
iii. When ultrasound probe picks up echoes it measure frequency; different to frequency which has gone out -> Doppler shift -> work out which way the blood is flowing
iv. Put a measuring cursor on the screen which feeds into a Doppler frequency equation
What can be measured with a Doppler ultrasound?
i. Allows you to measure speed of blood flow as well as direction ii. Is their blood flow? What direction is it? How fast is it?
How does MRI work?
i. Body is made up of H -> spinning with positive charge -> small magnetic field
ii. In the body there are many spinning protons which magnetic moments -> line up when placed in strong magnetic field (MRI) -> net orientation in line with the magnetic field
iii. Images which are constructed so that you rely on how the magnetization reverts to normal iv. Two parameters in the formulae to describe how magnetization get back to where it was - T1, T2 constants 1. Weight sequencing so that you make use of T1 or T2 2. T1 = (stationary) fluid are black on T1 3. T2 = (stationary) fluid are white on T2
What are the dangers of MRI?
Need to avoid anything metalic
- Cant be used if someone has a pacemaker etc
What percentage of the liver’s blood supply comes from the portal vein and hepatic artery?
What relative oxygen contribution do they make?
i. Portal vein = 75% ii. Hepatic artery = 25%
Both contribute about 50% of the oxygenation
Where is the bifurcation of the aorta?
L5
What are the layers of the anterior abdominal wall?
Skin Superficial fascia 3 flat layers of muscle Deep fascia (transversalis fascia) Extra peritoneal Peritoneum
Where is rectis abdominis found?
Either side of the midline. Vertically
What is the visceral and parietal peritoneum?
The peritoneum lines the walls of the cavity where it is called the parietal peritoneum - it reflects off the abdominal wall at various points to surround visceral structures
- Visceral (where it surrounds viscera) vs parietal
What is the pubic tubercle?
The pubic tubercle is the bump of bone at the lateral end of the pubic crest
What replaces the 3 flat muscles of the anterior wall medially?
Aponeurosis
What is an aponeurosis?
It is a flat, broad tendon. They have a shiny, whitish-silvery color, arehistologically similar totendons, and are very sparingly supplied withblood vesselsandnerves,
What happens to the two aponeurotic extensions in the midline?
They interdigitate in the midline, knitting together to form a vertical raphé - this is called the linear alba (meaning white line)
What is the ASIS?
Anterior superior iliac spine
What type of muscle is the external oblique?
It is a front pockets muscle (downwards and forwards)
Where does external oblique end superiorly?
It overlaps onto the front of the thoracic cage, it comes up to and edge to edge with pec major and serratus anterior
Where does external oblique attach anteriorly?
Attaches tot he anterior half of the iliac crest, as far as ASIS.
It then jumps to the pubic tubercle and pubic crest
What is the free edge of external oblique, why does it exist?
The jump of external oblique from the ASIS to the pubic tubercle and crest creates the free inferior edge.
The free inferior margin is thickened and turns under itself forming what is called the inguinal ligament.
What happens after the externa; oblique attaches inferiorly?
The free inferior edge attaches to the pubic tubercle and then there is a triangular opening in the aponeurotic part of external oblique before the final attachment to the pubic crest
What type of muscle is internal oblique?
It is a back pockets muscle (directed downwards and backwards)
Where does internal oblique attach superiorly?
It attaches directly onto the costal margin
Where does the internal oblique attach inferiorly?
The Internal oblique attaches to the iliac crest as far as the ASIS.
The lowermost fibres of the internal oblique take origin from the lateral 2/3rds of the inguinal ligament.
Where are the fibres of the internal oblique that attach to the inguinal ligament heading?
These fibres do not head to the linear alba to meet with the lowermost fibres of internal oblique from the other side, rather they are arching Upwards Over and Down to insert into the pubic crest on their own.
What is the arrangement of the fibres in the transversus abdominus?
The muscle has horizontal/transversely arranged fibres.
Why are the muscles of the transversus abdominus arranged transversely?
The reason for this arrangement is for strength, the strongest anterior wall upon contraction will come from having 3 different fibre directions
What functions are controlled (in part at least) by the contraction of the abdominal muscles?
Defacation, urination, childbirth, coughing
Where transversus abdominus insert superiorly?
This muscle underlaps the costal margin and is in the same plane as the diaphragm.
Where do the transversus abdominus and internal oblique end posteriorly?
They extend around as far as the thorico-lumbar fascia
Where do the lowermost fibres of the transversus abdominus arise from?
The lowermost fibres come off the iliac crest and then continue to arise from the lateral part of the inguinal ligament (lateral 1/3)
How are the muscles of the transversus abdominus arranged inferiorly?
They do not go to the linea alba, rahter they arch upwards over and downwards to insert into the pubic crest (like internal oblique)
Do transversus abdominus and internal oblique insert into the pubic crest together?
Transversus abdominus and internal oblique are intimately related to one another so they insert into the pubic crest via a conjoined tendon
Where does the rectus abdominus arise inferiorly?
The pubic crest
What happens to the fibres of rectus abdominus as it ascends?
They diverge
Where does rectus abdominusn attach superiorly?
It crosess the costal margin and attaches to the the costal margins of 5,6,7 (it is basically edge to edge with pec major)
What is the issue with long muscles?
They are generally not very powerful
Why does rectus abdominus have a series of tendinous intersections in its verticle ascent?
It creates muscle fibres which are shorter and thus stronger
Where are in intersections of rectus abdominus?
Umbilicus
xiphisternum
One in between
How do each of the aponeurosis cross the midline?
The three aponeurosis then create an envelope, fascia or an aponeurotic envelope or sheath around rectus abdominus as they head to the midline (linear alba)
Which side of the rectus abdominus do each of the aponeurosis cross the midlinein the upper rectus sheath?
The external oblique aponeurosis goes in front forming the front of the rectus sheath, the transversus goes behind and the internal splits with half going in front and half behind.
Where does the conformation of the aponeurotic crossover change?
About an inch below the umbilicus
In the lower recuts sheath how do the aponeurosis cross the midline?
All of the aponeurosis go in front of the rectus abdominus forming the anterior rectus sheath. There is no posterior rectus sheath.
What is the line of demarcation where the posterior rectus sheath cuts out?
It is an arched demarcation called the ARCUATE LINE
Where is the neuromuscular plane located in the anterior abdominal wall?
Between the internal and deep layers (between teh internal oblique and transversus abdominus)
Where is the umbillicus?
T10
What is the level of the groin?
L1
What are the blood vessels of the abdomeninal wall?
The main arterial supply is from a superior and inferior epigastric from above and below.
These vessels run in the rectus sheath.
They run deep to rectus abdominus in the posterior part of the rectus sheath
Where does the superior epigastric come from?
It is a branch of the internal throacic
Where does the inferior epigastric come from?
It is a branch of the external iliac artery
Why is drainage of the anterior abdominal wall important in portal hypertesnsion?
The site of overlap (between portal and systemic venous drainage) become importnant when a patient has portal hypertension.
The anterior abdominal wall is one of the sites of porto-systemic anastomoses
What is the venous drainage of the anterior abdominal wall?
The superficial and deep veins accompany the arteries
What is the lacuna ligament?
The lacuna ligament is the crescentic extension onto the pectineal bone
What is the pectineal ligament?
The linear extension from the pectineal ligament is called the Pectineal line
Where do the testis develop?
The testis develop in the extra peritoneal fat on the posterior abdominal wall (quite high up)
What do the testis need to get through to get into the scrotum?
Transversalis fascia
Transversus abdominus
Internal oblique
External oblique
Where is the cremaster muscle, what does it do?
○ These are the fibres which produce testicular retraction when it is cold
○ The muscle fibres particularly come from internal oblique
○ The fibres are arranged in whirls around the structure.
How do the testis get through the fascia transversalis?
- Testis create a deficiency in fascia transversalis half way between the ASIS and the pubic tubercle and a fingers breadth above the inguinal ligament
The hole created by the testis is called the Deep inguinal ring
How do the testis get through Transversus abdominus and Internal oblique?
- The lower most fibres arise from the lateral part of the inguinal ligament and arch upward over and downward and insert into the pubic crest
Thus if the testis turn medially and in the direction of the whole in external oblique they can travel through the arch formed by the arching fibres of transversus abdominus and Internal oblique which travel down to from the conjoined tendon and insert into the pubic crest.
This is called the inguinal canal, the entry point is the deep/internal inguinal ring
How do the testis get through external oblique?
- The inguinal ligament attaches to the pubic tubercle and then there is a triangular gap before continuing on in its attachment to the pubic crest
- This is called the external or superficial inguinal ring
Where does the nerve supply and vasculature of testis come from?
As the testis descends they take with them their nerve supply, veins, arteries and lymphatic as well the vas deferens (its duct) into the scrotum. These are the structures which comprise the spermatic cord.
What happens as the testis cross each layer of the anterior abdominal wall?
As the spermatic cord travels through each of the layers of the anterior abdominal wall it gets a layer of covering (i.e. by the end they have 3 layers and are very well protected)
What is the layer of covering the testis get from the deep ring?
Internal spermatic fascia
As the testis turn medially and pass the arching fibres of transversus abdominus and Internal oblique another layer is added this is called the….
Cremasteric fascia it is called this because there are some muscle fibres associated with it (crematsa)
What is the layer of covering the testis get from the external ring?
External spermatic fascia
It is only at this point that it is technically called the spermatic cord
What is an abdominal hernia, how does it occur?
When intra-anterior abdominal wall contracts and intra-abdominal pressure rises and everything gets to crowed, there is a propensity for the contents to find a way out (I.e. a point of weakness).
The abnormal protrusion of abdominal contents through the abdominal wall is called an abdominal hernia.
What are the causes of an abdominal hernia?
congenital or postoperative
eg If the layers of the abdominal wall are not stitched up properly after an operation a hernia can occur
What is an inguinal hernia?
The abnormal protrusion of the abdominal contents into the inguinal canal is called an inguinal hernia.
The contents could be pushed back into the abdominal region and the internal/deep ring could be sown up to prevent herniation in the future.
This can be omentum (commonly) or loops of bowel
What is an indirect inguinal herniae?
It is called an indirect hernia because it has to go through quite an indirect route in order to through to the scrotum. It is possible to get bilateral direct inguinal hernia where the contents of the abdomen are pushing through the weakest part of the anterior abdominal wall. The weakest part of the anterior wall in the inguinal region relates to the posterior wall of the inguinal canal.
What is a direct inguinal hernia?
A direct inguinal hernia , it has nothing to do with the deep ring. Rather it is just bulging out through the region of the inguinal canal through the posterior wall. (it does not enter the scrotum)
Where is an inguinal hernia likely to occur?
Between the inferior epigastric artery and the rectus abdominus is the weakest part of the anterior abdominal wall - it is quite easy for the inguinal contents to bulge through at this point.
It is called the inguinal triangle
What is a sliding hiatus hernia?
Stomach protrudes out of Abdominal Cavity. Generally from Reflux.
What us a rolling/paraoesophageal hernia?
Volvus hernia (twist of the stomach)
What is Mekel’s diverticulum?
Small bulge (outpouching) in SI at birth
What are some reasons why the bowel may be narrowed?
Adhesions (most common)
Volvus
Abdominal wall hernia
What is a ileo-anal pouch operation?
a surgically constructed internal reservoir; usually situated near where the rectum would normally be. It is formed by folding loops of small intestine (the ileum) back on themselves and stitching or stapling them together. The internal walls are then removed thus forming a reservoir. The reservoir is then stitched or stapled into the perineum where the rectum was. The procedure retains or restores functionality of the anus with stools passed under voluntary control of the patient.
What is an ileostomy?
- LI is not functioning.
* Drain waste externally through portion of ileum
What is achalasia?
A failure of smooth muscle fibers to relax, which can cause a sphincter to remain closed and fail to open when needed. Without a modifier, “achalasia” usually refers to achalasia of the esophagus, which is also called esophageal achalasia,
What does achalasia lead to?
Barret’s oesophagus
What are some of the sequale of duodenal ulcers?
Internal bleeding, Infection, scar tissue
They often require surgery
Why does one need to be careful when performing surgery on the gall bladder?
- A lot of variation around anatomy of gallbladder
* Ie cystic duct can be long/short or join right hepatic bile duct.
What is a laproscopoy and a laparotomy?
Laprascopy: -> AKA minimally invasive surgery AKA keyhole surgery
• Surgery made with small incisions (1cm) into abdomen.
Laprascopy: ->AKA minimally invasive surgery AKA keyhole surgery
• Surgery made with small incisions (1cm) into abdomen.
What forms the paravertibral gutters?
It is the projection of the 5 lumbar vertebrae
What floors the paravertibral gutters?
Powerful longitudinal muscles
What is psoas major?
It is a pair of muscles directly adjacent to the vertebral column
What overlies psoas major in 2/3rds of cases?
psoas minor
What muscles are lateral to the psoas major?
Quadrartus lumborum is superolateral
Iliacus is inferolateral
Locate psoas major
Lies in the paravertebral gutter, adjacent to the lumbar vertebral body
It is directly adjacent to the lumbar vertebral bodies, overlying the lumbar transverse processes
What is the origin of psoas?
Psoas has one continuous origin, from the lower boarder of T12 to the upper boarder of L5
What is the role of psoas?
It is an important flexor of the vertebral column, it is important in maintaining an erect spine
When it weakens one often gets an increased lumbar lordosis
What is psoas attached to?
Because it is a strong muscle and needs to be well anchored it is attached at both the lumbar vertebral bodies but also the disk in-between
i.e. it attaches from T12-L5 to the vertebral disks and to the medial ends of the transverse process
What happens in the inferior region of psoas?
The fibres converge (after L5), pass beneath the inguinal ligament and insert into the lesser trochantor of the femur
Where is the lumbar plexus located?
The Lumbar plexus is within psoas, the lumbar vessels are behind psoas and the sympathetic trunk is in front of psoas (as well as psoas minor if it is present)
Where are the lumbar vessels located?
The Lumbar plexus is within psoas, the lumbar vessels are behind psoas and the sympathetic trunk is in front of psoas (as well as psoas minor if it is present)
Where is the sympatheitc trunk located?
The Lumbar plexus is within psoas, the lumbar vessels are behind psoas and the sympathetic trunk is in front of psoas (as well as psoas minor if it is present)
What is the character of psoas minor?
Long slender tendon and a short slim belly - which means it is phylogenetically degenerating (i.e. disappearing from the species)
It blends with the periosteum of the pelvis and peters out (it does not do very much)
Where does quadratus lumborum attach?
Attaches above the 12th rib
It attaches to the tips of the transverse processes and to the posterior half of the iliac crest below
What is the role of quadratus lumborum?
It is a stabiliser of the 12th rib and a lateral flexo
Where is illiacus located?
Below quadratus lumborum
What shape is iliacus?
It is an inverted triangle shape
Where does the iliacus arise attach inferiorly?
The iliac bone has a smooth fossa on its internal surface called the iliac fossa.
This is where the iliacus arises
Where does the iliacus insert
It is edge to edge with psoas and the fibres converge to pass beneath the inguinal ligament from which it heads to the lesser trochanter
What is the common insertion of the iliacus and psoas called?
Called the conjoined tendon - the iliopsoas
What encloses each of the muscles?
Fascia
How many layers does the thoracolumbar fascia have?
3 (trilaminar structure)
To be precise it is only really 3 layers in the lumbar region
What are the 3 layers oif the thoracolumnar fascia?
One layer attached to the tip of the spinous process, this is the thoracolumbar posterior layer
A second layer is attached to the tip of the lumbar transverse process, this is the middle layer
There is a 3rd layer which is attached to the anterior region of the transverse process, this is anterior layer
Where do the 3 layers of thoracolumbar fascia fuse?
All three of the layers fuse laterally, along the line of the 12th rib