Companat: Chapter 1 (Muscular System)

Smooth muscle tissue

responsible for the contractile functions of the internal organs, lines the excretory ducts of glands, forms the blood and lymphatic vessel walls,

Striated muscle

can be further divided into the skeletal and the heart musculature

Smooth muscle, Striated Muscle

Two types of muscle tissue according to morphology and function

Somite cells

of the middle germ layer differentiate into mesenchymal stem cells, thus marking the embryonal beginnings of muscle cells.

Premyoblasts - Contractile Myoblasts

The mesenchymal stem cells differentiate further into

Myosin, Actin

Myoblasts contain proteins responsible for the contractility of the cell.

Myosin, Actin

These proteins are specifically arranged in the cytoplasm according to muscle cell type, creating a typical striation.

Muscle Fibres

Neighboring cells tend to fuse together, forming long, cylindrical, multinucleated cells

Muscle Fibres

in the adult animal can reach up to 10cm in length and 100μm in diameter.

Contractile Muscle Belly, Tendons of origin and insertion

A skeletal muscle can be divided into three general parts:

Tendons

attach to each end of the muscle belly and transfer the force generated by contraction of the belly to the skeleton.

cytoplasmic contractile myofilaments.

The muscle cells differ according to the number and thickness of their

sarcoplasma

cytoplasma of the muscle cell

White Muscle Type

contains proportionately more myofilaments, then the muscle stores less myoglobin and appears pale

White Muscle Type

This type of muscle tires quickly, but its contractile strength is great.

Red Muscle Type

contains less myofilaments and therefore can store more myoglobin in the sarcoplasma (i.e. in older domesticated and wild animals).

White and Red Muscle Type

Architecture of skeletal musculature and the tendons

Unipennate, Bipennate,Multipennate

Muscles are classified according to their structure and fibre orientation

Unipennate muscles (m. unipennatus)

with two parallel tendon sheaths

Bipennate muscles (m. bipennatus)

with double tendon sheaths, and

Multipennate muscles (m. multipennatus)

with multiple tendon sheaths

m. fusiformis

Spindle-shaped muscles

m. planus

Wide muscles

Wide muscles (m.planus)

whose tendon builds an aponeurosis

m. biceps

Two-headed muscles

m. triceps

Three-headed muscles

m. quadriceps

Four-headed muscles

biventer, digastricus

Two-bellied muscles

m. orbicularis

Circular muscles

m. sphincter

Sphincter muscles

Fasciae, Bursae, Tendon Sheaths

The muscles are supported in their many functions through passive structures such as the:

Fasciaea

Muscles are individually sheathed in

Fasciaea

expansive, thin and mesh-like sheets consisting of mostly collagen but also elastic fibres.

Synovial bursae

enclosed in a capsule of connective tissue.

Synovial bursae

ound everywhere in the body where muscles, tendons or ligaments glide over bone.

Inconsistent or facultative bursae

may develop subcutaneously at various sites subjected to constant mechanical pressure.

Synovial bursae

• Subtendinous bursae (bursae synoviales

subtendinosae),

• Submuscular bursae (bursae synoviales

submusculares),

• Subligamentous bursae (bursae synoviales

subligamentosae)

• Subcutaneous bursae (bursae synoviales subcutaneae).

Synovial tendon sheaths

similar to the bursae, except that they completely sheathed the tendons like a tube, protecting the underlying tissues from pressure exerted by the tendon and reducing friction during movement.

Tendon Sheaths

often form when the synovial membrane of a joint forms a recess (recessus), which then surrounds the tendon.