Abdominal wall Flashcards
What are the boundaries of the abdominal cavity?
- Cranial limit: diaphragm
- Caudal limit: pelvic inlet
- Abdominal wall around the outside (external, internal abdominal oblique, transversus abdominis)
- Ventrally abdominal wall (rectus sheath, rectus abdominis, linea alba)
What are the layers of the abdominal wall going from outside to inside
- Skin
- Fat
- External abdominal oblique
- Internal oblique
- Transverse abdominus
- Rectus abdominus
In what direction do the fibres of the external abdominal oblique muscle run?
- Caudoventrally (/)
- “hands in pocket”
What is the function of the external abdominal oblique?
- Compression of abdominal cavity
- Rotation of trunk
What are the origins and insertions of the abdominal oblique muscle?
- Origin: costal cartilages
- Insertion: wide aponeurosis forming inguinal ligament
In what direction do the fibres of the internal abdominal obliue muscle run?
- Fibres run cranioventrally
- “Ymca” muscle (\/)
What is the function of the internal abdominal oblique muscle?
- Opposes rotation caused by the external oblique
- Compresses diaphragm
What are the origins and insertions of the internal abdominal oblique muscle?
- Origin: coxal tuberosity, transverse process of lumbar vertebra, iliac fascia
- Insertion: linea alba and final rib costal arch
In what direction do the fibres of the transverse abdominal muscle run?
- Transversely across the abdomen (=)
- Sling type muscle
What is the function of the transverse abdominal muscle?
- Compress ribs
- Provides stability
What are the origins and insertions of the transverse abdominal muscle?
- Origin: transverse processes of lumbar vertebrae, ribcage
- Insertion: linea alba
In what direction do the fibres of the rectus abdominal muscle run?
- Longitudinally on both sides of the linea alba (II)
What is the function of the rectus abdominal muscle?
- Assists in breathing and abdominal stability
What are teh origins and insertions of the rectus abdominal muscle?
- Origin: sternum, sternal rib cartilage
- Insertion: prepubic tendon and pecten of pubic bone
What is unusual about the rectus abdominus compared to the other abdominal muscles?
- Lies within sheath
- Has tendinous intersections (transverse bands of fibrous tissue across muscle)
What muscles are innervated by the ilioinguinal nerve?
- Internal and external oblique
- Transverse abdominal muscles
Where does the ilioinguinal nerve originate from?
L2
What muscles are innervated by the iliohypogastric nerve?
- Internal external abdominal obliques
- Transverse abdominal muscles
What structures are innervated by the genitofemoral nerve?
- Sensory and motor to inner thigh
- Cremasteric reflex, contraction when superior medial part of thich is touched
What areas are supplied by the cranial abdominal artery?
- Transversus abdominus
- Internal abdominal obliques
What areas are supplied by the deep circumflex iliac arteries?
- Skin of caudal abdominal area
- Flank
- Cranial thigh
Describe the anatomy of the inguinal canal
- Floor is inguinal ligament
- Formed from external oblique aponeurosis as it folds over and inserts
- More of a slit
- in males testes pass through here
Describe the crura of the diaphragm
- Right arises from vertebral bodies and intervertebral fibrocartilages of the first 3 lumbar vertebrae
- Left arises from the first 2 lumbar vertebrae
Describe the costal attachments of the diaphragm
Lower costal cartilages adn ribs by digitations
What are the openings in the diaphragm?
- Aortic hiatus
- Oesophageal hiatus
- Caval foramen (fixed to diaphragm and so moves with diaphragm)
What is the importance of the hiati in the diaphragm?
- Not attached to structures
- Herniation can easily occur
What structures pass through the diaphragm to the abdomen?
- Oesophagus
- Aorta
- Vena cava
- Nerves via sympathetic chain
- Hemiazygous vein
Describe the peritoneum
- Serous membrane which lines abdominal cavity
- 3 sections
- Sac between different sections called peritoneal cavity
- Peritoneum can excrete and resorb fluid (function in disease and peritonitis) and resorb gas
- Peritoneal fluid normally present in peritoneal cavity and acts as lubricant
- Diseases include peritonitis, neoplasia and haemorrhage
What are the 3 layers of peritoneum?
- Parietal (lining body wall)
- Visceral (lining abdominal organs)
- Connecting (forming mesentery)
What are the layers of teh body wall?
- Skin, epidermis, dermis and subcutis
- External fascia of trunk
- Deep sheet of external fascia
- External abdominal oblique
- Internal abdominal oblique
- Transversus abdominis
- Internal fascia of trunk (transverse fascia) and peritoneum
Describe the rectus sheath
- Tendinous sheath, encloses rectus abdominis
- Formed by aponeuroses of other abdominal muscles
Describe the linea alba
- Fibrous tissue
- Aponeurotic joining of left and right abdominal oblique and transversus muscles
- Extends from xiphoid process to pubis
- Includes umbilicus
- Wide cranially, narrows caudally
- Strongest point for abdominal incisions
Describe the innervation of the body wall
- Ventral branches of thoracic and lumbar nerves (T13, L1 and L2)
- Skin of abdomen supplied by dorsal and ventral rami of spinal nerves
- Muscles and deep structures supplied by ventral rami
- Nerves pass obliquely in caudal direction
- T13, L1, L2 exit from vertebra foramina at associated transverse processes
- Go in caudal direction so by the tips of transverse processes are positioned at L1, L2 adn L4
Describe a paravertebral nerve block
- Used as anaesthetic for paralumbar approach in large animals
- Can be blocked proximally (dorsal aspect of T13, L1 and L2) or distally (ventral to lateral tips of L1, L2, L4)
Describe the vascular supply to the abdominal wall
- Cranial region: internal thoracic artery adn cranial epigastric artery (branch of brachiocephalic trunk)
- Diaphragm: phrenicoabdominal artery (branch of abdominal artery)
- Caudal region: caudal epigastric artery and external pudendal artery (branch of external iliac artery)
Describe the anatomy of the inguinal canal
- 2 regions, superficial and deep inguinal ring
- Superficial between 2 tendons of external abdominal oblique
- Deep is on caudal border of internal abdominal oblique
- Testes descend through here
What structures are in the inguinal canal?
- Spermatic cord in males
- External pudendal artery and vein
- Genitofemoral nerve
- Lymphatics
