Anatomy of the Abdominal Wall, Inguinal Region and Hernias Flashcards
What are the bony landmarks of the abdomen?
Sternum and xiphoid process
Costal margin, costal cartilages and ribs
Iliac crest, iliac fossa and anterior superior iliac spine (ASIS)
Pubic symphysis, pubic tubercle and pubic ramus
Thoracic and lumbar vertebrae, sacrum and pelvic bones
What visceral structures are found in the abdomen?
Stomach, duodenum and small intestines Liver, pancreas and spleen Kidneys, ureters and urinary bladder Reproductive organs Abdominal vessels
What are the 9 regions that the abdomen can be divided into (from top right to bottom left)?
Right hypochondriac, epigastric, left hypochondriac
Right lumbar, umbilical, left lumbar
Right iliac, hypogastric/suprapubic, left iliac
What are the two fascia found immediately below the skin and what are their characteristics?
Camper’s Fascia - fatty fascia
Scarpa’s Fascia - membranous layer
What muscles make up the posterior wall of the abdomen?
Quadratus lumborum, psoas major and iliacus muscles
Post-vertebral muscles (erector spinae group)
What muscles make up the lateral wall of the abdomen?
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External oblique
Internal oblique
Transversus abdominis
What muscles make up the anterior wall of the abdomen?
The paired vertical rectus abdominal muscles within the rectus sheath.
What is an aponeurosis?
Thin but strong fibrous sheet of tissue that replaces a tendon in muscles that are flat and sheet-like and have a wide area of attachment.
What are some functions of the three sheet-like muscles?
Compresses the abdomen and increases intra-abdominal pressure to aid expiration and evacuation of faeces, urine and parturition, heavy lifting.
Supports viscera - guards the intestines
Flex and rotate the trunk
What are the attachments of the external oblique?
External surfaces of the bottom 8 ribs
Free posterior border
Xiphoid process, linea alba, pubic crest and tubercle, anterior 1/2 of the iliac crest
State the direction of the external oblique muscle fibres.
Infero-medially
How is the inguinal ligament made and where does it attach?
Formed by the rolling inwards of the lower aponeurotic border of the external oblique. It extends from the anterior superior iliac spine (ASIS) to the pubic tubercle
What are the attachments of the internal oblique?
Laterally: thoracolumbar fascia, anterior 2/3 of iliac crest, lateral 1/2 of inguinal ligament
Medially: lower 3 ribs and costal cartilages, xiphoid process, rectus sheath and conjoint tendon
State the direction of the muscle fibres of the internal oblique.
Infero-laterally
What are the attachments of the transversus abdominis?
Laterally: bottom 6 costal cartilages, thoracolumbar fascia, anterior 2/3 of the iliac crest, lateral 1/3 of the inguinal ligament
Medially: xiphoid process, linea alba, pubic symphysis, conjoint tendon
State the direction of the muscle fibres of the transversus abdominis.
Horizontally
Where does the neurovascular layer lie?
Between the internal oblique and the transversus abdominis
What are the points of attachment of the rectus abdominis?
5-7 costal cartilages, xiphoid process
Pubic symphysis, pubic crest
What structures divide the rectus abdominis into segments?
Transverse tendinous intersections
What is the rectus sheath formed by?
The aponeuroses of the three flat muscles.
Describe the arrangement of the rectus sheath above and below the arcuate line.
Above the arcuate line - the internal oblique splits to encase the rectus abdominis. The external oblique is anterior to the rectus sheath and the transversus abdominis is posterior to the rectus abdominis.
Below the arcuate line - all three sheet muscles are anterior to the rectus abdominis. The posterior surface of rectus abdominis is in contact with the transversalis fascia.
What is the function of the rectus abdominis?
It is a powerful flexor of the vertebral column.
What are the points of attachment of quadratus lumborum?
Lower border of the 12th rib
Transverse process of lumbar vertebra 5
Adjacent iliac crest
What are the points of attachment of psoas major?
Bodies of all five lumbar vertebra
Lesser trochanter of the femur
What plane carries the nervous and blood supply to the abdominal wall?
Neurovascular plane - found in between the internal oblique and the transversus abdominis
Describe the blood supply to the rectus sheath.
Superiorly, blood supply comes from the superior epigastric artery, which is the terminal branch of the internal thoracic artery.
Inferiorly, blood supply comes from the inferior epigastric artery, which is a branch of the external iliac artery.
The two vessels anastomose providing a potential by-pass of the abdominal aorta.
Which vessels supply the flank muscles?
Intercostal arteries 7-11
Subcostal artery
Lumbar arteries
Deep circumflex iliac artery
What nerves supply the abdominal wall?
T7-L1
What nerves supply the external oblique, internal oblique and transversus abdominis?
External Oblique - T7-T11
Internal Oblique - T7-L1
Transversus Abdominis - T7-L1
What nerves supply the rectus abdominis?
T7-T12
Describe the difference in the innervation of the visceral and parietal peritoneum.
The parietal peritoneum has the same segmental somatic sensory innervation as the abdominal wall.
The visceral peritoneum has NO somatic sensory innervation
Which three nerves supply the antero-lateral abdominal wall?
Subcostal nerve (T12), Ilioinguinal nerve (L1), Iliohypochondriac nerve (L1)
Which nerves provide the motor supply for quadratus lumborum, psoas major and iliacus?
Quadratus Lumborum - T12-L4
Psoas Major - L2-L4
Iliacus - L2-L4
Where is the lumbar plexus located?
L1-L4
Which line defines a border between the lymphatic drainage to different groups of lymph nodes?
Transumbilical plane
Where do the superficial lymphatics above and below the transumbilical line drain to?
Above - pectoral group of axillary lymph nodes
Below - superficial inguinal lymph nodes
Where do the deep lymphatics above and below the transumbilical line drain to?
Above - mediastinal lymph nodes
Below - external iliac and para-aortic lymph nodes
Where does the inguinal ligament attach to the pelvis?
Anterior superior iliac spine and the pubic tubercle
Why is the inguinal region clinically important?
It is an area of inherent weakness where most abdominal hernias occur.
What defines the ends of the inguinal canal?
The superficial and deep inguinal rings
How long is a normal inguinal canal?
4 cm
Are hernias more common in males or females?
More common in males
What are the contents of the inguinal canal in males and females?
Males - spermatic cord + ilioinguinal nerve
Females - round ligament of the uterus + ilioinguinal nerve
At what stage in intrauterine life do the testes usually enter the inguinal canal and drop into the scrotum?
Testicular descent starts at 7 weeks IUL. They enter the inguinal canal around 28 weeks IUL and enter the scrotum around 32-36 weeks IUL
What passes through the femoral canal?
Efferent lymphatics and a lymph node
NOTE: the femoral artery and vein do NOT go through the femoral canal (the femoral vein, in fact, is the lateral wall of the femoral canal)
Define hernia.
Protrusion of part or a whole of an organ or tissue through the walls of the structure that contain it.
What are the three main parts of a hernia?
Weakness/hole, hernial sac, contents of the hernial sac
What are some clinical symptoms and signs of a hernia? What symptoms indicate that the hernia should be treated as an emergency situation?
Swelling or protrusion in the groin area
Pain/lack of pain and discomfort
May be intermittent or presenting all the time
May be reducible or irreducible
Strangulation may occur leading to tissue death causing symptoms such as vomiting, constipation and intestinal obstruction - this is considered an emergency
What factors increase the risk of femoral hernia in women?
Age and number of pregnancies
Where are the superficial and deep inguinal rings positioned?
Superficial inguinal ring is located immediately above and medial to the pubic tubercle
Deep inguinal ring is 1.5 cm above the midpoint of the inguinal ligament
The superficial and deep inguinal rings are holes in which muscles/fascia?
Superficial inguinal ring is a hole in the external oblique
Deep inguinal ring is a hole in the transversalis fascia
What is the conjoint tendon?
The lowest fibres of the internal oblique and the transversus abdominis come together to form the conjoint tendon, which attaches medially to the pubic crest .
What makes up the four walls of the inguinal canal?
Anterior - external oblique (the whole way) + internal oblique (lateral 1/3)
Posterior - transversalis fascia + conjoint tendon medially
Superior - arching over fibres of the internal oblique and transversus abdominis and the conjoint tendon medially
Inferior - inguinal ligament (folding inwards of the lower border of the external oblique aponeurosis)
What region do direct inguinal hernias occur through and where is this region positioned?
Hesselbach’s Triangle - medial to the inferior epigastric vessels
Where is the defect in indirect inguinal hernias positioned?
Dilation of the deep inguinal ring - lateral to the inferior epigastric vessels
What type of patients tend to have direct inguinal hernias and what behaviours and defects are direct inguinal hernias associated with?
Older patients - it is associated with chronic straining and weak musculature
It is caused by a defect in the posterior abdominal wall.
What type of patients tend to have indirect inguinal hernias?
Young adults and children
What type of patients are more likely to get femoral hernias?
Women and the elderly
What makes up the walls of the femoral canal?
Where is an inguinal hernia usually seen on the surface
Superior - inguinal ligament
Inferior - pectineus fascia
Medial - lacunar ligament
Lateral - femoral vein
Where is a femoral hernia usually seen on the surface?
Below and lateral to the pubic tubercle
Where is an inguinal hernia usually seen on the surface?
Where is an inguinal hernia usually seen on the surface?
