Case 12- anatomy Flashcards
Borders of the abdomen
- Superior border- diaphragm, costal margin
- Inferior border- Iliac crest, anterior superior iliac spine, inguinal ligament, pelvic crest, pelvic brim.
- Central landmark- umbilicus (belly button). At the bottom of the midline you have the linea alba which is a tendon which connects the xiphoid process to the pubic symphis
4 quadrant model of the abdomen
Splits the abdomen into 4 zones. The vertical line is the midline, the horizontal line runs through the umbilicus (trans umbilicus plane). Based on anatomical and theoretical landmarks
Right upper quadrant of the abdomen
Right lobe of the liver, gallbladder, pylorus of the stomach, first 3 parts of the duodenum, head of the pancreas, right kidney and adrenal gland, distal ascending colon, hepatic flexure of colon, and right half of the transverse colon
Left upper quadrant of the abdomen
Left lobe of the liver, spleen, stomach, jejunum, proximal ileum, body and tail of the pancreas, left kidney and adrenal gland, left half of the transverse colon, splenic flexure of the colon, superior part of the descending colon.
Right lower quadrant of the abdomen
Majority of the ileum, caecum, vermiform appendix, proximal ascending colon, right ureter, part of the bladder, uterus, ovary and uterine tube (female) or ductus deferens (male).
Left lower quadrant of the abdomen
Distal descending colon, sigmoid colon, left ureter, part of the bladder, uterus, ovary and uterine tube (female) or ductus deferens (male).
9 region model of the abdomen
The two vertical lines are the mid-clavicular lines, the two horizontal lines are the sub-costal (through the 10th costal cartilage) and the trans-tubercular lines which is between the tubercles on the iliac crest.
Right Hypochondriac region
Liver, gallbladder, small intestine, ascending colon, transverse colon, right kidney.
Epigastric region
Oesophagus, stomach, liver, spleen, pancreas, small intestine, transverse colon, parts of the left and right kidney, adrenal glands and ureters
Left Hypochondriac region
Stomach, part of the left lobe of the liver, left kidney, spleen, tail of the pancreas, parts of the small intestine, transverse colon, descending colon.
Right lumbar region
Part of the liver, gallbladder, small intestine, ascending colon, right kidney
Umbilical region
Stomach, pancreas, small intestine, transverse colon, parts of the kidneys and ureters, cisterna chyli
Left lumbar region
Small intestine, part of the descending colon, part of the left kidney
Right Iliac region
Small intestine, appendix, caecum, ascending colon, right ovary and uterine tube (female), ductus deferens (male)
Hypogastric region
Small intestine, sigmoid colon, rectum, urinary bladder, right and left ureters, uterus (female), ovaries and uterine tubes (female), ductus deferens, seminal vesicle and prostate (male).
Left Iliac region
Small intestine, descending colon, sigmoid colon, left ovary and uterine tube (female), ductus deferens (male)
How many layers does the anterior abdominal wall have
9
Flat muscles in the anterior abdominal wall
There are three flat muscles whose fibres run in different directions for strength. The three flat muscles end in the aponeurosis which contains rectus abdominus muscles. It is supplied by the thoracoabdominal nerves and epigastric arteries.
1) External oblique muscle
2) Internal oblique muscle
3) Transversus abdominus muscle
Role of the anterior abdominal wall
The abdominal wall helps contain the abdominal organs, move the trunk, used in forced breathing and increase intra-abdominal pressure (excretion/birth).
Layers of the anterior abdominal wall
From superficial to deep
Skin–> Camper’s fascia (fat) –> Scarpa’s fascia (membrane)–> External oblique muscles –> Internal oblique muscles –> Transversus abdominus muscles –> Transversalis fascia –> Extraperitoneal fat –> Parietal peritoneal
External oblique muscle
Most superficial muscle. originates on the outer surface of the lower 8 ribs. It inserts on the iliac crest. Has an aponeurosis (tendon) which ends in the midline raphe (linea alba). The free edge forms the inguinal ligament.
Internal oblique
Deep to the external oblique. Originates from the thoracolumbar fascia posteriorly. As well as the iliac crest and the inguinal ligament. It inserts on the lower three or four ribs. Forms an aponeurosis which ends in the linea alba. Attaches to the pubal crest and pectineal line.
Transversus abdominus
Originating from the thoracolumbar fascia posteriorly, the iliac crest, the inguinal ligament and the costal cartilages of the lower 6 ribs. It inserts in the pubic crest and pectineal line and forms and Aponeurosis ending in the linea alba. Final layer
Rectus abdominus
Not part of the layers of the abdominal wall as its only in the central region. Originates in the pubic crest, pubic tubercle and pubic symphysis. It inserts in the costal cartilages of ribs 5 to 6 and the xiphoid process. Forms the 6 pack
Pyramdalis muscle
A small triangular muscle that is found superficial but inferior to the rectus abdominus muscle. It attaches to the pubis bone and the linea alba. Function is to tense the linea alba, is not present in everyone.
Rectus sheath
A covering which encloses the rectus abdominus muscle and the pyramidalis muscle.
Aponeurosis
A sheet of fibrous tissue which has a wide area of attachment, often appears white
Linea alba
Midline where rectus sheath fuses, fusion of posterior and anterior wall of the rectus sheath.
Linea semilunaris
The lateral edge of the rectus sheath on each side
Arcuate line
5 to 6cm below the umbilicus level, where the posterior wall of the rectus sheath finishes
What forms the rectus sheath above the arcuate line
Superior 75% of the rectus sheath
• The anterior wall is formed from the aponeuroses of the external oblique and half of the internal oblique.
• The posterior wall is formed by the aponeuroses of half the internal oblique and the transversus abdominus.
What forms the rectus sheath below the arcuate line
The inferior 25% of the rectus sheath
• The anterior wall is formed by the aponeuroses of the external oblique, the internal oblique and the transversus abdominis.
• There is no posterior wall -the rectus abdominis is in direct contact with the transversalis fascia
Innervation of the thoracoabdominal wall
The thoracoabdominal nerves which originate from the spinal nerves
The neurovascular plane
Between the internal oblique and the transversus abdominus. It contains the vessels and nerves which supply the skin and muscles of the anterolateral abdominal wall. The nerves and vessels are transversely orientated and segmental
Blood supply to the abdominal wall
The epigastric arteries. The superior and inferior epigastric artery anastomose, providing collateral circulation between the subclavian and external iliac arteries
Superior epigastric artery
Arises from the internal thoracic artery. It enters the rectus sheath and descends on the posterior surface the rectus abdominis. Anastomoses with the inferior epigastric artery.
Inferior epigastric artery
Arises from the external iliac artery above the inguinal ligament. It enters the rectus sheath and ascends between the rectus abdominis and the posterior layer of the rectus sheath.
Superficial epigastric arteries
Arises from the femoral artery and runs superiorly toward the umbilicus over the inguinal ligament.
Venous drainage of the abdominal wall
Through the epigastric veins which follow the arteries. The paraumbilical vein from the portal system anastomoses with the epigastric veins from the caval system. Portal hypertension can cause varices in this area which creates caput medusae.
Characteristics of the Jejenum
Wall- thick Diameter- larger Vasa recta- long Arcades- few Fat in mesentery- less Circular folds (plicae circulares)- numerous, prominent Peyer's patches- no (few)
Characteristics of the Ileum
Wall- thin Diameter- smaller Vasa recta- short Arcades- many Fat in mesentery- more Circular folds (plicae circulares)- fewer, less prominent Peyer's patches- yes (many)
The small intestine
Assists in absorbing and digesting food, is 6 to 7m long. The jejunum makes up 2/5 of the small intestine while the ileum makes up 3/5. The duodenum is the first part of the small intestine.
Attachments of the small intestine
The small intestine is attached to the posterior abdominal wall by folds of peritoneum (the mesentery). Vessels pass between the two layers of mesentery to the small intestine.
Jejenum location
The jejenum begins at the Duodenojejunal junction, it is mostly found in the LUQ.
Ileum location
The Ileum ends at the Ileocecal junction and is mostly found in the RUQ
Arterial arcades
Where the arteries unite to form loops. The arterial arcades then give rise to the straight vasa recta. The arterial arcades provide back up vessels if the blood supply is occluded, reducing the risk of ischaemia.
Circular folds
Found in the inner mucosal lining of the small intestine surrounding the lumen. They increase the surface area of the small intestine for absorption
Palpating during a rectal exam- anal canal
Pectinate line, ischioanal fossae, bony structures (coccyx and sacrum), walls of the rectum, anal sphincter muscles and other related structures.
Palpating during a rectal exam- males
Prostate gland, rectovesical pouch, base of bladder (in some cases), seminal vesicles if enlarged, bulb of the penis
Palpating during a rectal exam- females
Retrouterine pouch (pouch of Douglas), cervix in some cases, retroverted uterus
Hernia
A hernia is a protrusion of an organ or tissue through its covering into an abdominal position outside its normal compartment. This usually occurs through a weak area of muscle or the surrounding tissue or due to increased intra-abdominal pressure.
Hernia risk factors
Age, obesity, previous surgery, ascites, pregnancy, heavy lifting, constipation and chronic cough.
Hernia classification
- Location-anatomical position
- Development-congenital vs acquired
- Potential for complications-reducible vs irreducible
Reducible hernia
Can be pushed back into its original position
Incarcerated (irreducible) hernia
Unable to push back into its original position
Obstructed hernia
The hernia contents are compacted causing bowel obstruction as the bowel lumen is not patent
Strangulation hernia
Squeezing of the hernia causes ischaemia due to lack of blood supply to the tissue
Indirect hernia
More common than direct hernias. The peritoneal sac (and potentially bowel) enters the inguinal canal via the deep inguinal ring. The degree to which the sac herniates depends on the amount of processus vaginalis still present. Large herniations are possible-reaches the scrotum.
Direct hernia
Direct inguinal hernias are acquired (usually in adulthood) due to weakened abdominal muscles. The peritoneal sac bulges into the inguinal canal via the posterior wall and can enter the superficial inguinal ring. The sac is not surrounded by the coverings of the contents of the canal.
Difference between direct and indirect hernias
Direct hernias are medial to the inferior epigastric vessels. Indirect hernias are lateral to the inferior epigastric vessels and enter the inguinal canal through the superficial inguinal ring.
Femoral hernias
Uncommon, 3:1 women to men ratio. Femoral hernias occur when the abdominal viscera or omentum passes through the femoral ring and into the femoral canal. Early repair is required. High rate of strangulation.
Different types of umbilical hernia
- Omphalocele-congenital
- Infantile- associated with prematurity
- Adult- associated with pregnancy, obesity and ascites
Paraumbilical hernia
Central swelling usually above or below the umbilicus. May become very large. More common in adults (especially women). May be associated with obesity and weak abdominal muscles. The sac may contain both the bowel and the omentum.
Incisional hernias
Occurs as a result of abdominal surgery incision, very common. Can reoccur after repair
Risk factors for incisional hernia
- Pre-op -elderly, obesity, diabetes, steroid use
- Intra-op- open surgery, sutures, technique
- Post-op-wound infection, chronic cough, abdominal distension
Epigastric hernias
Occurs through a defect in the linea alba. This is an area of relative weakness. Commonly in men aged 20-50. Sometimes there are multiple herniations. Differential diagnosis is diastasis recti (widening of linea alba but no defect). Need surgical repair due to risk of complications.
Obturator hernias
Elderly women, or patients with chronically raised intra-abdominal pressure. Protrudes from the pelvic cavity through the obturator foramen. Can cause bowel obstruction. Difficult to diagnose-palpable on rectal/pelvic examination only.
Spigelian hernia
High risk of strangulation. Small tender mass at the lower lateral edge of the rectus abdominus. Occurs at the semilunar line around the level of the arcuate line
