A27 - Mm. abdominis, canalis inguinalis

Question 1

Muscles of the abdominal wall

Give the general featurs/structures of the abdominal wall

Answer 1

• The abdominal muscles carry considerably weight of abdominal viscera, especially in herbivores
• Suspension bridge: forms a bridge and flexible connection between the thorax, lubar region and pelvic girdle
• Umbilicus
  
  • ​Linea alba forms a fibrous ring in its middle: anulus umbilicalis
• Lacuna musculorum:
  
  • ​Gap between
    
    • Cranial border of pelvis
    • Lig. inguinalis
    • Lamina/fascua iliaca
  • Allows m. iliopsoas and m. sartorius (ø ca) to pass from the abdominal and pelvic cavities into the thigh
• Lacuna vasorum
  
  • ​Ventrolateral to the lacuna muscles
  • Opening
  • Bordered by:
    
    • Lig. inguinalis
    • Corpus ossis ili
  • Permits passage for:
    
    • A/V/L. iliaca externa
    • A/V/L. fermoralis profunds
• Tunica flava abdominalis (ø ca)
  
  • Reinforcement of abdominal wall in herbivores
• Anulus inguinalis superficialis
  
  • ​M. obliquus abdominalis externa tendon forms the:
    
    • Crus pelvina (lateral)
    • Crus femoralis (mediale)
  • Superficial inguinal ring: slit between them
• Anulus inguinalis profundus
  
  • ​Borders:
    
    • Lig. inguinale (part of m. obliquus externa)
    • M. obliquus abdominalis interna
    • M. rectus abdominis
• Canalis inguinalis
  
  • ​Male:
    
    • Goes to the scrotum and testicles
  • Female: Also present
  • Passage for processus vaginalis
  • Blood and lymph vessels runs to the:
    
    • Male: penis (spermatic cord)
    • Female: fatty tissue

Question 2

Give the muscles of the abdominal wall

Answer 2

1. M. obliquus externus abdominalis
2. M. obliquus internus abdominalis
3. M. transversus abdominalis
4. M. rectus abdominalis

Question 3

M. obliquus externus abdominalis

Answer 3

Carnivores:

• Origin:
  
  • Fascia thoracolumbaris lamina superficialis (Ø ru)
  • Lateral aspect of the rib 4-12
• Insertion:
  
  • Fibers run caudoventrally \\
  • Linea alba
  • Lig. inguinale
• Action: Abdominal pressure
• Innervation:
  
  • ​R. ventralis ex nn. intercostalis
  • R. ventralis ex nn. costoabdominalis
  • R. ventralis ex nn. lumbalis

Horse:

• Origin:
  
  • ​Thoracic part: rib 4-18
  • Lumbar part: last rib & thoracolumbar fascia
• Insertion: tuber coxae
• Abdominal tendon
  
  • ​Reinforcement by tunica flava
  • Insertion:
    
    • Linea alba
    • Middle crus of external inguinal ring
    • Lig. pubicum, cranial

Question 4

M. obliquus internus abdominalis

Answer 4

Carnivores:

• Origin:
  
  • Thoracolumbar fascia lamina superficialis (ø eq)
  • Tuber coxae
  • Proximal part of the lig. inguinale
• Insertion:
  
  • Fibres run cranioventrally to linea alba ////
  • At preumbilical level - outer and inner layer - formation of rectus sheath
• Action: Abdominal pressure
• Innervation:
  
  • ​R. ventralis ex nn. intercostales
  • ​R. ventralis ex nn. costoabdominalis
  • ​R. ventralis ex nn. lumbalis

Horse:

• Origin:
  
  • ​Tuber coxae
  • Lig. inguinale
• Insertion:
  
  • ​Last rib
  • Last four costal cartilages
• Abdominal part:
  
  • Becomes an aponeurosis at the level of the lateral border of the rectus abdominis muscle
  • Blends with the abdominal tendon of the external obligue muscle – to form the outer layer of the rectus sheath
• In the inguinal region forms:
  
  • Medial wall of inguinal canal
  • Cranial border of internal inguinal ring

Question 5

M. transversus abdominalis

Answer 5

Carnivores:

• Origin:
  
  • Lubal vertebrae, processus transversus
  • Fascia thoracolumablis lamina profunda
  • Medial surface of false ribs
• Insertion:
  
  • Linea alba
  • Xiphoid cartilage
  • Fibres run transversely
• Action: Abdominal pressure
• Innervation:
  
  • ​R. ventralis ex nn. intercostales
  • ​R. ventralis ex nn. costoabdominalis
  • ​R. ventralis ex nn. lumbalis

Horse:

• Origin:
  
  • ​Rib 2-13
  • Lubal vertebrae, processus transversus
• In lumbar region:
  
  • Fibers become an aponeurosis
  • Forms the inner layer of the rectus sheeth
  • The caudal border of the muscle – at the level of the tuber coxae

Question 6

M. rectus abdominis

Answer 6

Carnivores:

• Origin: Sternum, cranial
• Insertion:
  
  • Pecten ossis pubis
  • Tendo prepubicus
  • Fibres run saggital
• Innervation:
  
  • ​R. ventralis ex nn. intercostales
  • ​R. ventralis ex nn. costoabdominalis
  • ​R. ventralis ex nn. lumbalis

Horse:

• 9-11 tendinous inscripitions – blendid with the outer layer of the rectus sheath
• Origin: 4th-9th costal cartilages
• Insertion:
  
  • ​Cranial pubic ligament
  • Tuberculum pubicum ventrale

Question 7

Give the rectus sheath in different zones

Answer 7

• Divided into:
  
  • Anterior lamina
  • Posterior lamina
• Thoracic: E - R - Thoracic wall
• Preumbilical: E - I - R - I - T - P
• Umbilical: E - I - R - T - P
• Postumbilical: E - I - T - R - P
• E: m. obliquus externus abdominalis
• I: m. obliquus internus abdominalis
• T: m. transversus abdominalis
• R: m. rectus abdominalis
• P: fascia transversa abdominalis & peritoneum

Question 8

Fascia abdominis transversa

Answer 8

• A thin aponeurotic membrane
• Lies between the inner surface of the transverse abdominal muscle and the parietal peritoneum
• Forms part of the general layer of fascia lining the abdominal wall
• Directly continuous with the iliac fascia, internal spermatic, and pelvic fasciae
• The spermatic cord in the male, the round ligament of the uterus in the female pass through the transverse fascia at the deep inguinal ring the entrance to the inguinal canal
• In the male the transverse fascia extends downwards as the internal spermatic fascia

Question 9

Linea alba

Answer 9

• White line
• Fibrous structure
• Runs down the midline of the abdomen
• Runs from the xyphoid process to the pubic symphysis
• Formed by the fusion of the aponeuroses of the abdominal muscles
• Separates the left and right rectus abdominis muscles
• It consists of mostly connective tissue
• Does not contain any primary nerves or blood vessels - a median incision through the linea alba is a common surgical approach

Question 10

Peritoneum

Answer 10

• Serous membrane
• Forms the lining of the abdominal cavity covers most of the intra-abdominal organs composed of a layer of mesothelium
• Supported by a thin layer of connective tissue
• Supports many of the abdominal organs
• Conducts blood vessels, lymphatic vessels, and nerves
• Continuous sheet
• Peritoneal cavity: two layers of potential space between them

Layers of peritoneum:

1. ​Parietal peritoneum (outer layer)
   
   • Attached to the abdominal wall and pelvic wall
2. Visceral peritoneum (inner layer)
   
   • Wrapped around visceral organs

Question 11

Inguinal canal

Answer 11

• Canalis inguinalis is passage for:
  
  • Male:
    
    • Spermatic cord (inside tunica vaginalis). Through channel towards scrotum to reach testicles
  • Female:
    
    • Processus vaginalis (inside fat and lig. teres)
  • In both genders:
    
    • A/V. pudenda externa
    • N. genitofemoralis
    • Eff. vessels (?) from ln. inguinalis superficialis
• Extends from peritoneum
• Anterior wall
  
  • Aponeurosis of m. obliquus externus
  • Superfiical inguinal ring
• Inferior wall (floor)
  
  • Lig. inguinale
• Superior wall (roof)
  
  • Medial crus of aponeurosis of m. obliquus externus
  • Musculoaponeurotic arches of internal oblique and transverse abdominal muscle
• Posterior wall
  
  • ​Fascia transversa abdominalis
  • Peritoneum
  • Deep inguinal ring
• Inner opening (deep ring)
  
  • Rostral: m. obliquus internus abdominalis
  • Caudal: lig. inguinale
  • Medial: m. rectus abdominis
• Outer opening (superficial ring)
  
  • Crus mediale (lamina abdominalis)
  • Crus laterale (lamina pelvina) from m. obliquus externus abdominis

Superficial inguinal ring:

• Lateral border: Lateral limb of m. obliquus externa
• Medial border: Medial limb of m. obliquus externa

Spatium inguinale:

• Loose connective tissue
• “Virtual” space between muscles (which leads from one opening to the other)
• Lateral border: pelvic ligament
• Medial border: M. obliquus interna

Deep inguinal ring:

• Cranial border: m**. obliquus interna
• Medial border: rectus abdominalis
• Caudal border: lig. inguinale

Question 12

What is special about abdominal msucles in horses?

Answer 12

The tendinous part of the abdominal muscles is larger