ANSC*2340: Forequarter and Hindquarter Muscles

neck muscles

• Produce tough meat because of their high connective tissue content.

• Usually removed from their bones (cervical vertebrae) and are used as strewing meat or ground beef.

• Only muscle worthy of passing note: sternomandibularis.

sternomandibularis

This neck muscle forms the superficial part of a compound muscle in the ventral throat region running from the head to the sternum. Because this muscle is severed when the head of a beef carcass is removed at slaughter, samples may be obtained immediately after slaughter without damaging a commercial carcass.

shoulder muscles

• Range from intermediate in their level of toughness to tender and are usually cooked in order to make them tender.

• Easily recognized group of muscles and bones enables meat to be readily identified.

• Of note: supraspinatus, infraspinatus, trapezius, rhomboideus, subscapularis, biceps brachii, triceps brachii.

supraspinatus

Should muscle dorsal to the spine or ridge on the scapula.

infraspinatus

Shoulder muscle ventral to the scapular spine.

trapezius

Shoulder muscle located superficially between the left and right scapular blades.

Figuratively, if one were to stab a standing animal between its shoulder blades, the knife would pass through this muscle first and then through the rhomboideus.

rhomboideus

Shoulder muscle ventral to the trapezius.

Figuratively, if one were to stab a standing animal between its shoulder blades, the knife would pass through the trapezius first and then through this muscle.

subscapularis

Shoulder muscle located on the flat medial surface of the scapula, towards the ribs.

biceps brachii

Shoulder muscle anterior to the humerus in an equivalent position to the biceps muscle in the human arm.

brachii

Adjective needed to indicate the biceps muscle of the arm, since there is another biceps muscle, the biceps femoris, located in the hindlimb.

triceps brachii

Large muscle located in the triangular area bounded by the ventral edge of the scapula and the posterior edge of the humerus.

Its name (three heads) indicates that his large triangular muscle is subdivided. Thus, when seen in a cut of meat from the shoulder, it may look like more than one muscle.

distal muscles of the limbs

• Produce tough meat because of their high content of connective tissue.

• Distal regions of the forelimb (shank) and hindlimb (leg) have groups of fusiform (cigar-shaped) muscles with long tendons with extend distally towards the toes or phalanges.

  • If these muscles are cut open longitudinally, it may be seen that most of them contain internal tendons that fan outwards for the attachment of short bundles of muscle fibres.

fusiform

Cigar-shaped.

pennate structure

A feather-like arrangement of muscles.

The distal regions of the forelimb (shank) and hindlimb (leg) have groups of fusiform (cigar-shaped) muscles with long tendons with extend distally towards the toes or phalanges.

If these muscles are cut open longitudinally, it may be seen that most of them contain internal tendons that fan outwards for the attachment of short bundles of muscle fibres.

The meat derived from these muscles is quite tough, because of their high connective tissue content.

extensors

Most of the distal muscles located anteriorly in the limb. When they contract in the living animal, they cause the toes to move forwards, as in the start of a new stride.

In beef and lamb carcasses, tendons from these muscles pass down the length of the cannon bone and are kept in place by ligamentous rings. Thus, the extremities of a limb are moved by remote control. Beef cannon bones are discarded in the abattoir because they have virtually no meat on them.

flexors

Most of the muscles located posteriorly in the distal part of the limb. Bend the limb during locomotion.

flexors and extensors

From the distal parts of the limbs, are difficult to identify individually once they have been removed from the skeleton.

muscles of the ribcage

• Several muscles located between the scapula and the ribcage.

• Hold the forelimb onto the body.

• Most are intermediate in their level of toughness.

• For most of the length, there are no major muscles immediately ventral to the heads of the ribs.

serratus ventralis

A large, fan-like muscle of the ribcage that radiates from the medial face of the scapula and attaches to the lateral surfaces of the ribs.

The major component of a muscular sling that suspends the thorax of an animal from between its forelimbs. The muscular sling that holds the forelimb onto the body serves as a shock absorber during locomotion.

• This muscular suspension system has no counterpart in the hindlimb since the pelvis is fused to the vertebral column.

longissimus dorsi

An extremely important muscle of the ribcage and loin. It forms the eye of meat seen when chops and steaks are cut from the posterior rib region and loin.

In reality, is a compound muscle composed of many subunits. Each subunit acts over the length of several vertebrae and helps flex the vertebral column.

Also involved in respiratory movements, as well as helping to move the neck.

The muscle fibre bundles are arranged at an acute angle to the vertebral column, The cross-sectional area increases towards the posterior part of the ribcage, but it has approximately constant cross-sectional area through the loin.

• Extends posteriorly from the rib region, runs through the loin, and most of the muscle terminates on the anterior face of the iilium.

• Dorsal to the transverse processes of the lumbar vertebrae; dorsal to the ribs in the thoracic region.

Beef carcasses are usually split into forequarters and hindquarters between ribs 12 and 13 - the area of this muscle seen at this point is often measured or examined in order to assess the amount of meat in a carcass (may be a useful guide to muscularity when comparing animals with a similar carcass length). However, in the comparison of long carcasses with short carcasses, a smaller cross-sectional area does not necessarily indicate a smaller muscle mass, since the mass is spread over a greater length.

pectoralis

Muscle of the ribcage located over the sternum in the brisket. Extends posteriorly into the plate.

Composed of deep and superficial layers. The intercostal muscles are located between adjacent ribs in the wall of the chest, and there are two layers in the depth of the muscle.

Intercostal muscles make an important contribution to the meat content of North American pork spareribs.

loin muscles

• Give rise to tender meat with a desirable taste, and they command a high price when presented for sale as stakes or chops.

• The longissimus dorsi extends posteriorly from the rib region, runs through the loin, and most of the muscle terminates on the anterior face of the iilium.

  • Thus, is seen in cuts of meat taken through the ribs and loin, but not in cuts of meat such as sirloin steaks that are posterior to the anterior face of the ilium.

• There are muscles both above and below the level of the transverse processes of the lumbar vertebrae.

  • Dorsal muscle above: longissimus dorsi.

  • Ventral muscle below: psoas major (filet muscle).

psoas major

Muscle found ventral the level of the transverse processes of the lumbar vertebrae. Originates ventrally to the last couple of ribs in the ribcage.

Continues posteriorily from the loin into the sirloin. Joined by the iliacus, the two together given a compound name (ilipsoas).

The cross-sectional area increases towards the sirloin.

psoas minor

Medial to the psoas major, found almost under the centra of the vertebrae.

multifidus dorsi muscles

Muscles found immediately lateral to the dorsal spines of the vetebrae (medial to the longissimus dorsi).

Has little commercial significance due to its small size, but may create a problem in the measurement of rib eye areas since they might be accidentally included with the longissimus dorsi.

longissimus costarum

A relatively small rope-like muscle found dorsal to the ribs.

It appears as a small eye of meat at the separation between the forequarter and the hindquarter.

Has little commercial significance due to its small size, but may create a problem in the measurement of rib eye areas since they might be accidentally included with the longissimus dorsi.

gluteus medius

Muscle located laterally in meat animals. Covers the lateral face of the ilium and appears as the large muscle area in sirloin steaks and chops.

From lateral to medial, there are three layers of muscles:

1. Gluteus medius

2. Gluteus accessorius

3. Gluteus profundus

iliopsoas

tensor fascia lata

hindlimb muscles

• Relatively large and produce a large volume of moderately tender meat.

• Orientation is necessary for the identification of all muscles here except for the gracilis and the sartorius.

gracilis

A thin sheet of muscle spread over the medial face of the hindlimb.

Together (with the small sartorius muscle anterior to this muscle), may be used to orient hindlimb cuts of meat such as a beef round steak or a slice of ham.

sartorius

Small muscle located anterior to the gracilis.

With the gracilis, may be used to orient hindlimb cuts of meat such as a beef round steam or a slice of ham.

quadriceps femories muscles

Form a group of four large muscles that pull on the patella when the leg is extended.

1. Vastus medialis

2. Vastus lateralis

3. Vastus intermedius

4. Rectus femoris

vastus medialis

A quadriceps femoris muscle. Located medially.

vastus lateralis

A quadriceps femoris muscle found laterally.

vastus intermedius

A quadriceps femoris muscle. Covers the anterior face of the femur.

rectus femoris

A quadriceps femoris muscle. Covers the vastus intermedius.

biceps femoris

A single large muscle on the lateral face of the hindlimb.

In cross section, it often appears to be divided into two parts because it has a very deep cleft along part of its length.

Appears as a single muscle in cuts of meat which miss the cleft, but sections through the cleft make the muscle appear double.

To add to the possibility of confusion, the small segment of muscle cut off by the cleft is often paler than the main part of the muscle.

semitendinosus

Large muscle located on the posterior face of the hindlimb. Located lateral to the semimembranosus.

semimembranosus

Large muscle located on the posterior face of the hindlimb. Medial to the semitendinosus.

In lean carcasses, may be difficult to separate from the adductor (may appear as a single muscle).

adductor

Muscle located in the medial part of the hindlimb, near to the femur. Posterior to the pectineus.

In lean carcasses, may be difficult to separate from the semimembranosus (may appear as a single muscle).

pectineus

Muscle located in the medial part of the hindlimb, near to the femur. Anterior to the adductor.

gastrocnemius

A large muscle located deep in the hindlimb, covered by distal extensions of some of the proximal muscles of the limb. Pulls on the Achilles tendon at the hock and is the equivalent of the calf muscle in the human leg.

The human muscle is not covered by the posterior thigh muscles.

sirloin muscles

Muscles located between the hindlimb and the loin, and located laterally to the pelvis = several large muscles that form the rump and sirloin of the carcass.

Very little of the longissimus dorsi appears here since most of the muscle terminates on the anterior face of the ilium.

iliacus

Joins the psoas major in the sirloin.

iliopsoas

Compound name between the iliacus and the psoas major when they join in the sirloin.

flank muscles

Formed by sheets of muscle and connective tissue. The muscles are relatively tough and need not be identified individually. The layers of abdominal muscles appear as the parallel layers of lean in a slice of side bacon.

tensor fascia lata

Triangular muscle located in the angle between the the animal’s flank and its hindlimb. Stretches the fascia lata during locomotion.

Due to suspension by hindlimbs when the animal leaves the abattoir (extreme rotation of the hindlimb relative to the vertebral column), this muscle is spread through the stretched muscle mass of the sirloin.

fascia lata

A sheet of connective tissue that covers the anterior surface of the hindlmib. Stretched by the tenor fascia lata during locomotion.