1. 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
Describe the the Abdominopelvic cavity
Abdominal and pelvic cavities are continuous
What separates the thoracic and abdominal cavities?
Diaphragm
What arbitrarily separates the abdominal from the pelvic cavity?
Pelvic inlet (pelvic brim)
Axis of abdominal cavity
Vertical
Axis of pelvic cavity
Downwards and backwards
What visceral structures are found in the abdominopelvic cavity?
Stomach, duodenum, small and large 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 planes are used to divide the abdomen into 9 regions?
Mid-clavicular planes Subcostal plane (L2) Intertubercular plane (L5)
How is the abdomen divided into 4 quadrants?
Vertical line down sagittal plane
Horizontal line across transumbilical plane
What muscles make up the anterior wall of the abdomen?
Paired vertical rectus abdominal muscles within the rectus sheath.
What muscles make up the lateral wall of the abdomen?
External oblique
Internal oblique
Transversus abdominis
What muscles make up the posterior wall of the abdomen?
Quadratus lumborum, psoas major and iliacus muscles
Post-vertebral muscles (erector spinae group)
What is the midline of the abdominal wall called?
Linea alba
What are the 2 fascia found immediately below the skin and what are their characteristics?
Camper’s Fascia: superficial fatty layer of subcutaneous tissue
Scarpa’s Fascia: deep membranous layer of subcutaneous tissue
Where do the 3 flank sheet muscles continue anteriorly?
As aponeurotic sheets
Contribute to the rectus sheath
Name 3 functions of the 3 sheet-like muscles
Compresses the abdomen and increases intra-abdominal pressure to aid expiration and evacuation of faeces, urine, parturition and heavy lifting.
Supports viscera - guards the intestines
Flex and rotate the trunk
What happens to the 3 flank muscles when they reach the anterior midline?
They become aponeurotic
Thin but strong fibrous sheets of tissue that replaces a tendon in muscles that are flat and sheet-like and have a wide area of attachment.
Fuse together to form an envelope around the rectus abdominus muscle (rectus sheath)
What are the attachments of the external oblique?
External surfaces of the bottom 8 ribs
Free posterior border
Fans out to 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
Downward and forward
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.
Extends from the anterior superior iliac spine (ASIS) to the pubic tubercle
Where do aponeurosis of external oblique fuse?
Medially with rectus sheath
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 conjoint tendon
State the direction of the muscle fibres of the internal oblique.
Infero-laterally
Downward and backward
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 (rectus sheath) pubic symphysis conjoint tendon
State the direction of the muscle fibres of the transversus abdominis.
Horizontally
Where does the neurovascular plane lie?
Between the internal oblique and the transversus abdominis
What are the points of attachment of the rectus abdominis?
Superior: 5-7 costal cartilages xiphoid process Inferior: Pubic symphysis pubic crest
What structures divide the rectus abdominis into segments?
Transverse tendinous intersections (which are attached to the anterior wall of the rectus sheath)
3 on each side
Describe the rectus abdominis muscle
Long strap muscle of the anterior abdominal wall enclosed in rectus sheath
2 heads
What is the rectus sheath formed by?
The aponeuroses of the 3 flat muscles
Describe the arrangement of the rectus sheath above and below the arcuate line.
Above the umbilicus: internal oblique aponeurosis splits to encase the rectus abdominis.
The external oblique aponeurosis is anterior to the rectus sheath and the transversus abdominis is posterior to the rectus abdominis.
Below the umbilicus (at arcuate line): all 3 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?
The most powerful flexor of the vertebral column
External and internal obliques of both sides important in this
Where do the rectus sheaths meet?
In the midline
Linea alba
What are the points of attachment of quadratus lumborum?
Lower border of the 12th rib
Transverse process of 5th lumbar vertebra
Adjacent iliac crest
What are the points of attachment of psoas major?
Bodies of all 5 lumbar vertebra
Lesser trochanter of the femur
What is the function of the posts major?
Flexor of hip and trunk
What is the function of the quadratus lumborum?
stabilises the 12th rib and a lateral flexor of the trunk
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: superior epigastric artery, which is the terminal branch of the internal thoracic artery.
Inferiorly: inferior epigastric artery, which is a branch of the external iliac artery.
The 2 vessels anastomose forming a potential by-pass to the abdominal aorta.
Which vessels supply the flank muscles?
Intercostal arteries 7-11
Subcostal artery
Lumbar arteries
Deep circumflex iliac artery
Describe the blood supply to the flank muscles
Flank muscles are segmentally supplied
Names of veins draining the abdominal wall
Deep veins bearing the same names accompany the arteries
What nerves supply the abdominal wall?
T7-T12 and L1
What nerves supply the external oblique, internal oblique and transversus abdominis?
External Oblique - T7-T11
Internal Oblique - T7-T12 and L1
Transversus Abdominis - T7-T12 and L1
What nerves supply the rectus abdominis?
T7-T12
No L1
Describe the difference in the innervation of the visceral and parietal peritoneum.
Parietal peritoneum has the same segmental somatic sensory innervation as the abdominal wall.
Visceral peritoneum has NO somatic sensory innervation
Dermatomes (sensory to skin) of abdominal wall
T7: Epigastrium
T10: Umbilicus
L1: Inguinal ligament
Which 3 nerves supply the antero-lateral abdominal wall?
Subcostal nerve (T12) Ilioinguinal nerve (L1) Iliohypogastric 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
Describe the lumbar plexus
Motor and sensory, mainly for the lower limb.
Sensory branches to the parietal peritoneum of the posterior abdominal wall
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
Lymph nodes on the abdominal wall
There are NO lymph nodes on the abdominal wall.
Lymphatic drainage of superficial vs deep tissue
Superficial lymphatics accompany subcutaneous veins. Lymphatic drainage in quadrants
Deep lymphatics accompany deep veins in the extraperitoneal tissues.
What is the inguinal region also known as?
Groin
Where does the inguinal ligament attach to the pelvis?
Anterior superior iliac spine (ASIS) and the pubic tubercle
What is the inguinal region?
Junction between the anterior abdominal wall and the thigh
What is weakened in the inguinal region?
Abdominal wall
Clinical and anatomical importance of inguinal region
Clinical: Site of abdominal hernias
Anatomical: Where structures exit and enter the abdominal cavity (e.g. spermatic cord, round ligament, vessels
What defines the ends of the inguinal canal?
The superficial and deep inguinal rings
How long is a normal inguinal canal?
4 cm
Are inguinal hernias more common in males or females?
Males
What are the contents of the inguinal canal in males and females?
Males: spermatic cord, genital branch of Genito-femoral nerve + ilioinguinal nerve
Females: round ligament of the uterus, genital branch of Genito-femoral nerve + ilioinguinal nerve
What are the 2 Areas of Inherent Weakness in the Groin?
Inguinal canal: site of descent of testis, spermatic cord and uterine round ligament
Femoral canal: below inguinal canal
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 ~28 weeks IUL and enter the scrotum ~32-36 weeks IUL
What passes through the peritoneal (femoral) sheath?
Femoral artery
Femoral vein
Femoral canal
What passes through the femoral canal?
Efferent lymphatics and a lymph node
Femoral artery and vein do NOT go through the femoral canal (the femoral vein is the lateral wall of the femoral canal)
What is outside the femoral sheath?
Femoral nerve
Define hernia.
Abnormal protrusion of part or a whole of an organ or tissue through the walls of the structure that contain it.
What are the 3 main parts of a hernia?
Weakness/hole: through which hernia protrudes
Hernial sac e.g. peritoneum with neck, body and fundus
Contents of the hernial sac e.g. bowel, bladder
What are some clinical symptoms and signs of a hernia?
Lump or protrusion in the groin
Pain/painless and uncomfortable
May be intermittent or present all the time
May be reducible or irreducible
May be strangulated with tissue death (associated with vomiting, constipation and intestinal obstruction)
What indicates that a hernia should be treated as an emergency situation?
Strangulation
What factors increase the risk of femoral hernia in women?
Age and number of pregnancies
Which type of hernia is more common?
Inguinal
Where are the superficial and deep inguinal rings positioned?
Superficial: immediately above and medial to the pubic tubercle
Deep: 1.5 cm above the midpoint of the inguinal ligament
The superficial and deep inguinal rings are holes in which muscles/fascia?
Superficial: hole in the external oblique
Deep: hole in the transversalis fascia
What is the conjoint tendon?
The lowest fibres of the internal oblique aponeurosis and the transversus abdominis aponeurosis join to form the conjoint tendon, which attaches medially to the linea alba
What makes up the 4 walls of the inguinal canal?
Anterior: external oblique aponeurosis (whole length) + internal oblique muscle (reinforces lateral 1/3 of canal)
Posterior: transversalis fascia + conjoint tendon medially
Superior: arching fibres of the internal oblique and transversus abdominis muscle (whole length) + the conjoint tendon medially
Inferior: inguinal ligament (Rolled inferior edge (gutter like) of the external oblique aponeurosis)
What are the 2 types of inguinal hernia?
Indirect
Direct
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
Associated with chronic straining and weak musculature
Caused by a defect in the posterior abdominal wall.
Hernia’s path straight through wall of inguinal canal
What type of patients tend to have indirect inguinal hernias?
Young adults and children
Which type of inguinal hernia is more common?
Indirect
Where is the path of indirect inguinal hernias?
Through the abdominal wall
Hernia enters the deep ring, passes through the inguinal canal, external inguinal ring and into the scrotum
What type of patients are more likely to get femoral hernias?
Women and the elderly
What is there a high incidence of in femoral hernias?
Obstruction
Strangulation
What makes up the walls of the femoral canal?
Superior: inguinal ligament
Inferior: pectineus fascia
Medial: lacunar ligament
Lateral: femoral vein
Where is a femoral hernia usually seen on the surface? What is there appearance?
Below and lateral to the pubic tubercle
Tend to be irreducible
Hot and painful if strangulated
Where is an inguinal hernia usually seen on the surface?
Above and medial to the pubic tubercle
