What is meant by the Girdle Musculature - what is their function? These muscles are also called the sub-lumbar muscles - why?
Think of what a girdle does:
The main function of the "girdle musculature" is to stabilise the vertebral column and pelvis during locomotion and for control of dorsiflexion and ventriflexion of the spine.
They are also called sub-lumbar muscles because they originate from the ventral aspect of the lumbar vertebrae and insert on either the pelvis (ox coxae) or the femur.
What are the girdle muscles aka sublumbar muscles?
Note: These are all innervated by the ventral branches of the lumbar nerves.
Origin: 2nd-3rd caudal thoracic vertebrae on their ventral aspect and the 4th/5th cranial lumbar vertebrae. Insertion: via a strong tendon to the psoas tubercle of the femoral shaft.
The strongest muscle of the girdle. Flexion of the hip and outward rotation of the stifle. ie. draws hindlimb forward.
In all animals, except carnivores, where they are fused, the muscle can be divided into two distinct parts:
Greater Psoas (lumbar portion) - Origin: last thoracic vertebrae and ribs and the bodies and transverse processes of the lumbar vertebrae. Insertion: Incorporates with iliac muscle and inserts on the lesser trochanter.
It is positioned dorsally to the psoas minor and ventral to the quadrate lumbar muscle.
Iliacus - Origin: wing and shaft of ilium. Insertion: via the common iliopsoas tendon to the lesser trochanter of the femur. The muscle passes through the muscular lacuna; an opening between the os coxae laterally and caudally, the rectus abdominus medially and the iliac fascia cranially.
Stabilises the lumbar vertebral column.
Origin: Ventral aspect of the transverse processes of the lumbar vertebrae and the proximal ends of the ribs. Insertion: Ventral aspect of the wings of the ilium and sacrum.
What is the function of the rump muscles?
The rump muscles' main function is to extend the hip and some also extend the stifle and tarsus. They can be grouped into four distinct groups:
medial muscles of the thigh
inner pelvic muscles.
What are the gluteals?
They form the prominence in the caudo-lateral aspect of the proximal hindlimb.
They are innervated by the cranial and caudal gluteal nerves.
Tensor Fascia Latae
What is the most power hip extensor in the body?
The middle gluteal muscle.
It also retracts & abducts the hindlimb.
This muscle also shows great species variance, though all species have a superficial and deep portion that are separated by a tendinous sheet. Both tendons on their site of insertion are protected by a synovial bursa.
What is the piriform muscle?
This is fused to the middle gluteal muscle except in carnivores. Like the other gluteals, it's an extensor of hip and abducter of the limb.
Origin - last sacral vertebrae and sacrotuberous ligament.
Insertion - just distal to the greater trochanter on the lateral aspect of the femur.
Location - caudal and medial to the middle gluteal and is covered by the superficial gluteal.
How is the function of the tensor fascia latae muscle different from the other rump muscles, ie., the gluteals?
The gluteals -- middle, superficial, deep -- are hip extensors and limb abductors.
The muscle of the tensor fascia latae, when contracting, tenses the fascia around the thigh (cranial aspect of the forelimb), causing FLEXION of the hip and EXTENSION of the stifle.
For this reason, the muscle of the tensor fascia latae is considered part of the passive stay of the hindlimb.
What are the caudal muscles of the thigh, also known as the hamstrings?
Caudal crural abductor muscle
What does the biceps femoris do?
The biceps femoris, which is the most superficial and lateral of the hamstrings, extends and abducts the limb. It has cranial and caudal parts; the caudal part extends the hip but flexes the stifle.
What are the differences between the semitendinosus and the seminmembrinosus?
Semitendinosus - Origin - the ischial tuberosity (pelvic head). Insertion - cranial margin of the tibia and a tendinous insertion on the calcaneal tuberosity.
It is superficial and lateral to the semimembrinosus.
Semimembrinosus - Origin - can be from either just the pelvic head or from the pelvic head and vertebral head. This is dependent on species. Insertion - onto the medial condyle of the femur and the medial condyle of the tibia. It is medial to the semitendinosus.
Which nerve innervates the hamstrings?
Which of the main muscle groups of the forelimb are responsible for adduction of the limb?
The medial muscles of the thigh:
Sartorius (long, superficial strap-like muscle)
Where is the pectineal (pectineus) muscle relative to the other medial thigh muscles, the Gracilis and the Sartorius?
Deep to and between the Gracilis & Sartorius.
Where are the adductor muscles relative to the other medial thigh muscles, the Gracilis and the Sartorius?
The adductor muscles are deep to the Gracilis & the Sartorius muscles. See illustration.
Origin - the tendinous plate of the gracilis muscles. Insertion - medial aspect of the femur, fascia and ligaments of the medial aspect of the stifle.
Adduction of the limb, can also retract the limb.
Where is the external obdurator muscle? (this is pretty minor compared to the other medial muscles of the thigh: sartorius, gracilis, pectineus & adductor).
It's also considered part of the internal pelvic muscles.
Origin - the ventral pelvic surface close to the obturator foramen.
Insertion - trochantic fossa.
What are the two main muscles that control the stifle joint?
The quadriceps femoris (four heads) and the popliteal muscle.
What are the four heads of the quadriceps?
These muscles form the main muscle bulk on the cranial aspect of the thigh, but is covered by the tensor muscle of the fascia lata, the sartorius and the medial femoral fascia.
Consists of four parts that have separate points of origin but have a common single tendon, the patella tendon that inserts onto the patella and tibial tuberosity.
The quadriceps are the main extensors of the stifle and the straight muscle also flexes the hip.
Of the four heads of the quadriceps, which one DOES NOT originate on the femur? Where does it originate?
Rectus femoris: Originates from the ilial shaft cranial to the acetabulum and runs down to the patella tendon between the two bellies of the lateral and medial vastus.
Where is the popliteus muscle and how does it affect the stifle joint?
It has a tendinous origin from the lateral condyle of the femur.
It inserts in a a broad tendon on the medial and caudal surface of the proximal tibia.
Location - On the caudal aspect of the stifle and runs under the lateral collateral ligament before it inserts. See photo.
It is a flexor of the stifle and pronator of the leg.
What is the nerve that innervates the four heads of the quadriceps femoris?
The femoral nerve innervates alll the muscles of the cranial thigh, ie., the quadriceps femoris (vastus medialis, vastus lateralis, vastus intermedius, rectus femoris).
The femoral nerve also innervate a muscle of the medial thigh. What is that muscle?
The sartorius muscle. The saphenous branch of the femoral nerve innervates the sartorius muscle.
All of the muscles of the medial thigh are innervated by the same nerve, except for the sartorius muscle, which is innervated by the saphenous branch of the femoral nerve. What is the nerve that innervates the medial thigh muscles, and what are the muscles?
The obturator nerve innervates all of the medial thigh muscles except for the sartorius muscle.
The other medial thigh muscles are the gracilis, pectineus and adductor muscles.