Unit 6 - Abdominal Wall and Abdominal Topography

How many lumbar vertebrae are usually present in the horse?

- Usually 6 lumbar vertebrae are present (sometimes five)

Describe the transverse processes of the lumbar vertebrae in the horse.

- Length increases to L3 or L4 then decreases to the last vertebra

- First two curve caudally, last two curve cranially

- L4 articulates with L5, L5 with L6, L6 with the sacrum

How many lumbar vertebrae are usually present in the ox?

- Usually 6 lumbar vertebrae are present, 6-7 in small ruminants

Describe the transverse processes of the lumbar vertebrae in the ox.

- Longer vertebrae than in the horse

- large articular processes; facets are curved

- Transverse processes all curve cranially, the shortest of which is L2. Length increases to L5, shorter on L6

Where does the ventral longitudinal ligament course?

- Courses from the sacrum to the mid-thoracic region

What forms the flank fold in the horse and ox?

- Cutaneous trunci m. and skin

What are the boundaries of the paralumbar fossa?

- Last rib

- Transverse processes of the lumbar vertebrae

- Tuber coxae

What is the subiliac lymph node also known as in the horse and the ox?

- Prefemoral lymph node

Where is the subiliac lymph node located in the horse?

- Located craniomedial to the tensor fascia latae muscles, halfway between the tuber coxae and patella

Where do afferents of the subiliac lymph node in the horse course from?

- Course form the skin and subcutis of the dorsal and lateral sides of the caudal thoracic, cutaneous muscles of the dorsal and lateral sides of the abdominal, lumbar, and pelvic regions, including the thigh and stifle joint, and from the tensor fasciae latae m.

Where do efferents of the subiliac lymph node in the horse course?

- Follow the ventral branches of the deep circumflex iliac vessels to the lateral and medal iliac lymph nodes

Where is the subiliac lymph node located in the ox?

- Located on the aponeurosis of the external abdominal oblique m. close to the tensor fasciae latae m.

Where do afferents of the subiliac lymph node in the ox course from?

- From the skin of the pelvic, thigh and leg regions and from the abdomen and caudal portion of the thorax, prepuce, tensor fasciae latae m., regional lymph nodes (coxal, accessory coxal, and paralumbar lymph nodes)

Where do efferents of the subiliac lymph node in the ox course to?

- Follow the ventral branches of the deep circumflex iliac vessels to the lateral and medial iliac lymph nodes

What are the vessels and nerves of the abdominal wall?

- Branches of the deep circumflex iliac artery (from external iliac artery or the aorta)

- Lateral cutaneous femoral n. (formed from ventral branches of L3, L4, +/- L5 spinal nerves)

What does the lateral cutaneous femoral n. innervate?

- Innervates skin in the craniomedial thigh region

What is the tunica flava abdominis (abdominal tunic)? What is its role? What does it cover ventrally and laterally?

- Deep fascia sheet of elastic tissue

- Assists the abdominal muscles in supporting the weight of the abdominal viscera

- Ventrally, it covers and adheres to the aponeuroses of the external abdominal oblique m.

- Laterally, it covers the external abdominal oblique, external intercostal, and serratus ventralis thoracis mm.

What is the linea alba? What is it formed by?

- Median fibrous raphe extending from the xiphoid cartilage to the prepubic tendon

- Formed by the junction of aponeuroses of external abdominal, internal abdominal and transversus abdominis mm.

What is the origin, insertion, innervation and action of the external abdominal oblique m. in the horse? Which way do the fibers run?

- O: Lateral surfaces of 4th -18th ribs and the fascia over the external intercostal mm.;thoracolumbar fasciaq

- I: Linea alba and prepubic tendon, tuber coxae and body of the ilium, medial femoral fascia

- Innervation: Ventral brs. of thoracic and lumbar spinal nn.

- Action: Compress the abdominal viscera as in defecation, urination, parturition and expiration; flex the trunk

- Fibers directed ventrocaudally

What is the origin, insertion, innervation and action of the external abdominal oblique m. in the ox? Which way do the fibers run?

- O: Caudal border and lateral surfaces of 6th-13th ribs and the fascia over the external intercostal mm.

- I: Tuber coxae and by aponeurosis to the prepubic tendon and linea alba

- Innervation: Ventral brs. of last 4-5 thoracic and first 2 lumbar spinal nn.

- Action: Compress the abdominal viscera, as in defecation, urination, parturition and expiration; flex the trunk

- Fibers directed horizontally in the flank

What is the origin, insertion, innervation and action of the internal abdominal oblique m. in the horse? Which way do the fibers run?

- O: Tuber coxae and adjacent part of the inguinal ligament

- I: Cartilages of the last 4-5 ribs; linea alba and prepubic tendon

- Innervation: Ventral brs. of thoracic and lumbar spinal nn.

- Action: Compress the abdominal viscera, flex the trunk

- Fibers course ventrally, cranially and medially

What is the origin, insertion, innervation and action of the internal abdominal oblique m. in the ox? Which way do the fibers run?

- O: Tuber coxae and deep lumbar fascia at the lateral border of longissimus lumborum m.

- I: Caudal border of the last rib, prepubic tendon, linea alba

- Innervation: Ventral brs. of last few thoracic and first 2 lumbar spinal nn.

- Action: Compression and support of the abdominal viscera

- Fibers course ventrally, cranially and medially

What is the origin, insertion, innervation and action of the transversus abdominus m. in the horse? Describe its structure.

- O: Medial surface of the ventral ends or cartilages of the asternal ribs and the transverse processes of the lumbar vertebrae via thoracolumbar fascia

- I: Xiphoid cartilage and linea alba

- Innervation: Ventral brs. of thoracic and lumbar spinal nn.

- Action: Compress the abdominal viscera, flex the trunk

- Dorsal part is muscular, ventral part is aponeurotic

What is the origin, insertion, innervation and action of the transversus abdominus m. in the ox? Which way do the fibers run?

- O: Deep lumbar fascia from the transverse processes of the first 5 lumbar vertebrae, medial surface of the ventral ends or cartilages of the asternal ribs, the transversalis fascia, and the caudomedial surface of the last rib

- I: Linea alba

- Innervation: Ventral brs. of thoracic and lumbar spinal nn.

- Action: Retract the ribs and compress the abdominal viscera

- Dorsal part is aponeurotic, costal attachment is muscular

What is the origin, insertion, innervation and action of the rectus abdominus m. in the horse?

- O: Cartilages of the 4th or 5th to 9th ribs and the adjacent surface of the sternum

- I: Pubis via the prepubic tendon

- Innervation: Ventral brs. of thoracic and lumbar spinal nn.

- Action: Similar to that of external and internal abdominal oblique mm. (abdominal compression); flex the lumbosacral joints and the lumbar and thoracic parts of the spine

What is the origin, insertion, innervation and action of the rectus abdominus m. in the ox?

- O: Ventral and lateral surfaces of the sternum as far cranially as the 3rd or 4th costal cartilage

- I: Pubis via the prepubic tendon

- Innervation: Ventral brs. of thoracic and lumbar spinal nn.

- Action: Similar to that of external and internal abdominal oblique mm. (abdominal compression); flex the lumbosacral joints and the lumbar and thoracic parts of the spine

What are the components of the rectus sheath? What does it surround? Where does it insert?

- Internal lamina

- External lamina

- Surrounds rectus abdominis m.

- Insertion: prepubic tendon on pecten pubis

What is the internal lamina?

- Aponeurosis of transversus abdominis m.; transversalis fascia

What is the external lamina?

- Fused aponeuroses of the internal and external abdominal oblique mm.

What is the origin, insertion, and action of the retractor costa m.?

- O: L1-L2/L3 transverse processes in ruminants; L1-L3/L4 in the horse

- I: caudal border of the last rib

- Action: retracts the last rib - aids in forced expiration

What provides innervation to the flank of ruminants?

- Dorsal and ventral branches of T13 (costoabdominal n.), L1 (Iliohypogastric n.), L2 (Ilioinguinal n.), and L3 (Genitofemoral n.)

What is important about performing surgery in the paralumbar region in ruminants?

- It is necessary to anesthetize the dorsal and ventral branches of T13, L1 and L2 spinal nerves: Paravertebral block and Paralumbar block

How does one perform a paravertebral block in ruminants?

- T13 spinal n. -> Palpate last rib and transverse processes of L1 and L2; Insert needle vertically 5 cm in ox (3 cm in sheep and goat) from dorsal midline in a transverse plane at the cranial angles of the tips of the transverse process of L1. Anesthetize both dorsal and ventral branches of T13

- L1 and L2 spinal nn. -> Make similar injections at the transverse planes at the caudal borders of the transverse processes of L1 and L2

What are the advantages and disadvantages of a paravertebral block in ruminants?

- Advantages: Uniform anesthesia of all structures of the paralumbar fossa including the peritoneum; Good muscle relaxation

- Disadvantages: Technique important to avoid puncturing the aorta, caudal vena cava or azygos v.; Paralyzes epaxial muscles on the side of the operation causing a convexity of the trunk; Viscera may bulge out of the incision; Closure is more difficult

How does one perform a paralumbar block in ruminants?

- T13 spinal n. -> Dorsal and ventral to the tip of L1 transverse process and between the last rib and transverse process

- L1 spinal n. -> Dorsal and ventral to the caudal edge of L2 transverse process

- L2 spinal n. -> Dorsal and ventral to the caudal edge of L4 transverse process

- May need additional injection midway between L3 and L4 vertebrae

What is the different regarding where the nerve are infiltrated in paravertebral and paralumbar blocks in ruminants:

- Paravertebral block: Nerves are infiltrated close to the vertebrae

- Paralumbar block: Nerves are blocked at the tips of the transverse processes

What are the advantages and disadvantages of a paralumbar block in ruminants?

- Advantages: Uniform anesthesia of all structures of the paralumbar fossa including the peritoneum; Good muscle relaxation; Epaxial muscles are not paralyzed

- Disadvantages: Possible individual variation in position of spinal nerves may necessitate additional injections

What does segmental lumbar epidural anesthesia block? What is the site of injection?

- Blocks T13, L1, and L2 spinal nerves

- Site of injection: Between L1 and L2 vertebrae (technically more difficult)

What must be blocked for anesthesia of the udder (excluding the caudal portion innervated by the pudendal n.)? How does this differ in the cow vs the ewe/doe?

- Need to block genitofemoral n. which arises from L3 spinal n. and often includes brs. from L2 and L4 nn.

- In cows - block ventral brs. of L1-L4 spinal nerves; In ewe and doe - block ventral brs. of L2-L4 spinal nerves

What separates the dorsal and ventral sacs of the rumen?

- Longitudinal groove

What are the leaves of the greater omentum in the ruminant and where do they course?

- Superficial leaf: Courses from the dorsal body wall on the right side to the left longitudinal groove of the rumen

- Deep leaf: Courses from the dorsal body wall on right side to the right longitudinal groove of the rumen

Which leaf of the greater omentum forms the supraomental recess in the ruminant?

- Deep leaf

What is the omental bursa? What protrudes into it?

- Space located between the superficial and deep leaves of the greater omentum

- Ventral sac of rumen protrudes into omental bursa

What covers the ventral sac of the rumen on the left side?

- Greater omentum

What is the omasum covered by on the right side?

- Lesser omentum

Where does the equine spleen course?

- Courses obliquely cranioventrally from the 15th -17th ribs to the ventral third of the 9th-12th intercostal spaces

The parietal surface of the equine spleen is in contact with what?

- The diaphragm

Where does the gastrosplenic ligament course in the horse?

- Between the hilus of the spleen and greater curvature of the stomach

Where does the nephrosplenic (renosplenic) ligament course in the horse?

- Between the spleen and left kidney

Where does the phrenicosplenic ligament course in the horse?

- Between the spleen and left crus of the diaphragm

Where does the dorsal extremity of the spleen lie in the ruminant?

- Lies under the dorsal ends of the last two ribs

What is the visceral surface of the ruminant spleen in contact with?

- Left side of the rumen

The dorsal part of the ruminant spleen is attached to what? The ventral part is __________.

- Attaches to the left crus of the diaphragm

- Free

The hilus of the ruminant spleen is located where?

- Located dorsally on the visceral surface

What takes up the majority of the right side of the paralumbar fossa in the horse?

- The base of the cecum