Part 14

The patella is provided with several ligaments, as follows:

The anterior patellar ligament, broad, strong, and irregular in thickness, extends from the inferior margin of the patella to the rim of the second tibial crest (Fig. 16, No. B, 3).

The ligamentum capsulare capituli fibulæ is spread out between the head of the fibula, or capitulum fibulæ, and the superficies glenoidalis peronea tibiæ.

FIG. 17.—Muscles and tendons of the head and posterior extremity.

A. Section of neck with superficial muscles removed. 1, Obliquo-transversales. 2, Interspinales. 3, Intertransversales. 4, Interarticulares.

B. Head showing muscles. 1, Beak. 2, Nostril. 3, Tongue. 4, Sublingual salivary gland. 5, Pterygoideus. 6, Stylo-hyoideus. 7, Temporal. 8, Flexor capitis inferior. 9, Rectus capitis lateralis. 10, Rectus capitis posticus major. 11, Trachelo-mastoideus. 12, Eye. 13, Mylo-hyoideus. 14, Genio-hyoideus. 15, Biventer maxilla. 16, Digastricus. 17, Rectus capitis anterior minor.

C. Foot of hen showing tendons. 1, Flexor perforans digitorum profundus. 2, Flexor perforatus medius primus pedis. 3, Sheath at joint through which tendon passes. 4, Flexor perforatus indicis primus pedis. 5, Flexor perforatus medius secundus pedis. 6, Flexor perforatus annularis primus pedis. 7, Flexor longus hallucis.

D. Outside view of leg of hen. 1, Biceps flexor cruris. 2, Semitendinosus. 3, Loop through which biceps flexor cruris passes. 4, Tibialis anticus. 5, Flexor perforatus indicis secundus pedis. 6, Flexor perforatus medius primus pedis. 7, Gastrocnemius. 8, Flexor perforatus annularis primus pedis. 9, Flexor perforatus medius secundus pedis. 10, Extensor longus hallucis. ]

The ligamentum tibio-fibulare extends from the head of the fibula, or capitulum fibulæ, to the inner surface of the external crest, or crista externa tibiæ, of the tibia (Fig. 25, No. 3).

The ligamentum interosseum is a delicate ligament located between the tibia and fibula (Fig. 25, No. 4) which very early becomes ossified.

=Ligaments of the Tibio-metatarsal Joint= (Fig. 16).—The tibio-tarsal joint is made up of the tibia and metatarsus.

The ligamentum capsulare ossis tibio-metatarsi connects the tibia and the metatarsus and surrounds the joint (Fig. 16, Nos. A, 7 and C, 7).

The ligamentum externum, a long strong ligament, originates on the upper and outer surface of the external condyle, or condylus externus of the tibia and is attached to the upper rim of the os metatarsi (Fig. 23, No. 15).

The ligamentum anticum is spread out between the fossa intercondyloidea of the tibia and the tuberculum ossis metatarsi of the proximal end of the metatarsus (Fig. 16, No. C, 3). Just posterior to this ligament, there is an interosseous ligament, the ligamentum interosseum.

A semi-lunar pad of fibrous cartilage, the cartilago semi-lunaris is located between the outer distal extremity of the tibia and upper articular surface of the metatarsus (Fig. 16, No. C, 6). Its concave portion is directed anteriorly and receives an insertion from the ligamentum externum, or external ligament.

The tendon Achillis (Fig. 16, No. A, 1) may become ossified.

=Ligaments of the Toes= (Fig. 16).—In addition to the capsular ligaments, which all true joints have, we find the following in connection with the toes:

The ligamentum superius and the ligamentum inferius connect the second toe with the great toe, or hallux.

The ligamentum laterale externum and the ligamentum laterale internum unite the bases of the second, third and fourth toes to the lateral faces of the trochleas of the inferior extremity of the metatarsus.

The bases of the toes are held together by the ligamenta transversa. All the rest of the toes are held together by the ligamenta capsularia digitorum pedis and by two lateral ligaments, namely: the ligamentum laterale externum and the ligamentum laterale internum.

MYOLOGY

=Kinds and Structure of Muscles.=—Muscles are highly specialized structures which have the property of contractility when stimulated, and thus produce motion. Muscular tissue is sometimes called flesh. Two kinds of muscles are recognized; muscles of locomotion and visceral muscles.

The muscles of locomotion may be in masses of different shape attached to the skin, the dermal, or to the skin and skeletal structure, the dermo-osseous, or from one bone to another, the skeletal. The visceral muscles form sheets and make up a portion of the wall of many of the hollow organs, such as the intestines, the stomach, the gizzard, the esophagus, and the blood-vessels. A special type of muscle forms the heart.

When classified with reference to structure, muscular tissue is divided into three types, as follows: voluntary-striated, involuntary, and involuntary-striated. The microscopic examination of each of these types of muscle shows it to be made up of fibers, these fibers to be made up of muscle cells, the muscle cell to be inclosed in a delicate tubular sheath, or membrane, called the sarcolemma. This membrane, tough and elastic, isolates each fiber. The bundles of fibers, called fasciculi, are surrounded by a fibrous sheath, which is called the perimysium internum; and the entire muscle has likewise an investing sheath of connective tissue, called the perimysium externum. The muscular cells show a longitudinal striation marking the fibrillæ, and they also show a cross striation. Nuclei are found just beneath the covering, or sarcolemma, in the striated muscle cell (Fig. 77, No. 2). In the involuntary and in the involuntary-striated muscle cell, the nuclei are centrally located.

The voluntary-striated muscles consist of cylindrical fibers and with a few exceptions, are under the control of the will. A muscle of this type, the regular skeletal form, usually has at each extremity a fibrous structure, called a tendon, by means of which it is attached to the bones. The intermediate fleshy portion of the muscle, in case of considerable bulk, is called the belly of the muscle.

The involuntary, non-striated, or smooth muscle, cells are spindle-shaped, long, and pale in color (Fig. 77, No. 1). The cells lie end to end forming fibers. These fibers do not terminate in tendons, but are arranged in sheets and aid in forming the walls of the digestive tract, to which they give the power of contraction and expansion.

Involuntary-striated, or heart muscle (Fig. 77, No. 4), occupies an intermediate position between the two muscles just described. It is composed of cells which branch, are somewhat rectangular. They possess both longitudinal and transverse striation. Among the fibers is found a small amount of connective tissue, as in the former types of muscle, which gives support to the blood-vessels and nerves.

=Fascia.=—The term fascia is applied to membranous expansions, differing materially in strength, texture, and relations. Fascia is composed of loosely arranged white fibrous connective tissue. At least two layers may usually be distinguished, the superficial fascia and the deep fascia.