Comparative Anatomy of Vertebrates

Skeleton of Fowl

Presented by

Diksha Sharma

Roll no- 620 Batch- 3

SKULLSkull is formed mostly with bony tissue.

 It consists of crani um, sense capsules, jaws and hyoid apparatus.

 It forms the median hollow part of the skull. It is divided into occipital, audi tory, orbital, olfacto ry and optic regions.

 Foramen magnum is posteriorly present.

Beneath the foramen magnum single occip ital condyle is present. Supra occipital, Exocci pitals & basioccipital bones are also present. Monocondylic skull.

 Each auditory capsule is formed largely by the prooticbone. Fenestra ovalis, fenestra rotun da, columella auris, stapes are also present.

The dorsal part of the cranium is formed by Parietals, frontals a rostum, alisphenoids; ventrally basisphenoid, basitemporal bones.

The two orbits are very large cavities present in front of the cranium. Eac h orbit is bounded dorsally by frontal, antero - dorsally by lac rimal and posteriorly by the zygomatic process. Orbit is incomplete on the ventral side. The two orbits are separated by inter orbital septum

 Each olfactory capsule is formed by two bones - Nasal and vomer. Nasals fuse withfrontals and form intosuper and inferior processes.

Each half of the upper jaw is formed by premaxilla, maxilla, quadratojugal, and jugal bones. The inner ar cade of the upper jaw forms the roof of bucco pharyngal cav ity which consists of palatine, pterygoid, and quadrate. 

Each half of the lower jaw is formed by articu lar, angular supra an gular, dentary and splenial. Both the jaws are lacking the teeth.

Pectoral Girdle

Girdle is well developed for flight.

The two halves of the girdle are broadly separated.

Each half is chiefly formed by the scapula,coracoid. The suprascapula is absent.

The glenoid cavity is formed between the coracoid and scapula.

The scapula is long and blade-eke. It is sabre shaped bone extending dorsally over the ribs and articulating anteriorly with the coracoid.

The scapula extends internally into an acromian process.

Clavicle bones are thin and attached dorsally to the scapula bones. These two are fused distally with the interclavicle to form furcula or Merry thought bone or wish bone.

At the junction of coracoid, scapula and clavicle bones foramen of triosseum is present.

Sternum is a separate bone with a keel along the mid ventral for the attachment of flight muscles.

Pelvic Girdle

 Pelvic girdle is large and pneumatic. It is well suited for bipedal locomotion.

Each os innominatum is formed by the ilium, ischium and pubis.

The bones are compactly fused.

 Ilium is long, thin and plate-like bone. It is differentiated into preacetabular and postacetabular regions.

Ilium articulates with synsacrum.

 Ischium a flat bone fused with the post acetabulariiium. They are separated by ilio-ischial foramen.

 llio-ischial foramen is large.

 Pubis is long, slender, curved bone. 11 lies ventral and parallel with ischial;;* Pubis

VERTEBRAL C

OLUMN

The number of vertebrae varies from 39 to 63, with remarkable variation (11 to 25) within the neck (cervical) series.

The principal type of vertebral articulation is heterocoelous (saddle shaped).

Each of the 3 to 10 (usually 5 to 8) chest (thoracic) vertebrae normally bears a pair of complete ribs consisting of a dorsal vertebral rib articulating with the vertebra and with the ventral sternal rib, which in turn articulates with the breastbone (sternum).

Each vertebral rib bears a flat, backward-pointing spur, the uncinate process, characteristic of birds.

The sternum, ribs, and their articulations form the structural basis for a bellows action, by which air is moved through the lungs.

Posterior to the thoracic vertebrae is a series of 10 to 23 fused vertebrae, the synsacrum, to which the pelvic girdle is fused.

Posterior to the synsacrum is a series of free tail (caudal) vertebrae and finally the pygostyle, which consists of several fused caudal vertebrae and supports the tail feathers.

FORELIMBESThere are four toes. The hallux is directed backwards and contain two phalanges.

 Humerus is a long & slightly flattened with a bent shaft associated by proxi¬mal and distal ends.

 The proximal end of humerus is highly expanded and form into the head A prominent deitcid ridge and a pneu¬matic foramen are present near the head. The distal end articulates with the radius and ulna by the articular surfaces. Supra trochlear fora¬men is absent.

 Radius is a straight and slender bone. It has a concavity for the articulation with humerus at the proxima end The distal end is convex.

Ulna is stouter and longer than radius It is slightly curved. A cranon process to blunt olecranon pro-cess is present at the proximal end. The distal ends of radius & ulna articulate with carpometacarpus.

 One smaller-radiate and a larger ulnare articulate with radius & ulna respec tively. The three dis tal carpals are fused with the meta carpa ls to form the carpometa carpus.

 The phalanges are the small bones sup port the fingers. The first finger has one, second has two and third has one phalan ges. Thus the phalan ges formula can be expressed as 1, 2, 1.There are no claws on the fingers.

HINDLIMBS

The bones of the hind limb are femur, tibia, fibula, tibiotarsus, tarsometatarsals and phalanges.

The femur is a stout bone of the thigh region. It has a long, curved shaft in the middle. The shaft has broad ends.

The proximal end of femur is produced into a rounded head for the articulation with the acetabulum. Opposite to the head a small protuberance greater trochanter is present.

There is an articular surface is present between the head and trochanter for the antitrochanter of ilium.

The distal end of femu has two prominent condyls with a intercondylar groove. Patella slides in the intercondylar groove on the anterior side. It is a disc-like sesm-oid bone.

Tibiotarsus fibula is formed of tibiotarsus and fibula. They are separate bones.

Fibula is small, slender bone. It is closely applied to the tibiotarsus.

The proximal row of tarsals are fused with tibia and forms tibiotarsus. The distal row of tarsals are fused with the metatarsals and forms tarso metatarsus.

There are four toes. The hallux is directed backwards and contain two phalanges.