16.07.2008

Feline Anatomy – Muscles

Author: breeder

Feline Anatomy – Muscles

Cats Have Highly Flexible Muscles

Feline Anatomy and Righting Reflex

 picture of cat anatomy - muscles

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Feature of feline anatomy are fast-acting, flexible muscles which ensure them graceful movements. Cats are good sprinters, but poor endurance athletes. The righting reflex allows cats to handle falls from a great height.

The cat’s balletic grace is due to both its skeleton and its highly flexible muscles, which are divided into three basic types. One is cardiac muscle, found only in the heart. The involuntary muscle that controls the other internal organs is called smooth, or non-striated, because this is how appears under the microscope.

The rest of the body’s muscles are called striated, or stripped and are controlled at will in all conscious or instinctive movements.

Feline anatomy: Muscle cells

Each individual muscle is made up of many muscle fibers held together by connective tissue. Muscle tissue consists of three different types of muscle cells.

Fast-twitch fatiguing cells. A cat’s muscle consists mostly of these cells, which work quickly but also tire quickly. They give a cats its speed and ability to leap several times its own length, but use up its energy in an instant.

Fast-twitch fatigue-resistant cells. Cats are poor endurance athletes. This is because they have relatively few fast-twitch fatigue-resistant cells, which work quickly but tire more slowly.

Feline Anatomy
Cat Righting ReflexCat’s righting reflex
The reflex that allows a cat to flip right-side-up depends on a flexible spine, resilient musculature, keen sight, and an efficient hearing apparatus.

Vets have observed that falls from five to ten floors are often fatal – cats reach 100 km/h after falling five floors, and the force of impact is too great to absorb.

Curiously, falls from even greater heights sometimes cause little injury, because, once the cat has righted itself, it assumes the skydiver’s free-fall position.

The muscular relaxation, taken with the deceleration effected by outstretched limbs, lessens the impact and injury.

Slow-twitch cells. These cells work and tire slowly and produce slow, sustainable contractions. They are called into play during hunting activities: they enable the cat to move almost imperceptibly slowly and stealthily, or wait for long periods in a ready-to-spring position.

Striped muscles are symmetrical across the body and under the control of the nervous system. Generally, striped muscles are arranged in opposing groups, performing opposing actions.

Feline anatomy: a Floating Shoulder
The cat’s shoulder is a feat of muscle, in that the forelimb is connected to the rest of the body only by muscle. Unlike our collarbone, which connects the shoulder and breastbone, the cat’s vestigial clavicle floats, anchored in place by muscle. The shoulder’s freedom of movement effectively lengthens the cat’s stride and enhances its range of motion.

The Feline Gait

When a cat walks, most of it forward movement comes from its hindlegs. Its forelegs act like brakes when they hit the ground, almost negating the slight push forwards they give on leaving it again.

The same is true when a cat trots. In this gait, the legs move in what is called contralateral fashion: the right front moves forwards together with the left hind, and vice versa.

Cat Anatomy Muscles: Pounces and Jumps

The cat’s pliant muscles and flexible spine allow it to curl up, or to rotate its body by 180 degrees in mid-air. This flexibility also gives the cat a repertoire of graceful leaping movements suitable for different circumstances.

When pouncing, a cat springs with its hindlegs, arches its back, and lands with its forepaws on its prize. Its refined wrist muscles allow it to rotate its wrists to grasp prey and to climb efficiently.

For a vertical jump, a cat judges the distance to be covered and calculates how much propulsive power from its hindleg muscles is needed.

This movement is different from the impromptu jumps a cat makes when chasing or being chased, and these, in turn, are different from the startle jump. In this, extensor muscles in all four legs activate simultaneously, and all the feet leave the ground at once, as if on springs.

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16.07.2008

Feline Anatomy – Bones and Joints

Author: breeder

Feline Anatomy – Bones and Joints

Cats are Built for Speed

Three Kinds of Joint Allow for Superb Flexibility

 picture of cat skeleton

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Feline Anatomy: Skeleton.The feline skeleton evolved for a lifestyle of speed and agility. A cat’s slender but robust legs support a narrow ribcage and a highly supple spine. Its shoulder blades are unattached to the main skeleton, permitting superb flexibility at any speed. The entire structure is held together by strong but elastic ligaments. The hard structure of the skeleton protects the internal organs, provides points of attachment for muscles, and acts as a system of levers and joints necessary for fluid movement.

Feline anatomy: The structure and growth of bone

Bones grow continuously during kittenhood. The skull begins as separate bones, to permit birth, and then fuses along suture lines. The long bones of the limbs and ribcage begin as hollow cartilage tubes; they calcify in infancy, becoming bone. Bones increase in length by production of bone at the growth plates, or epiphyses, at their ends. Epiphyses are nourished by a rich supply of tiny arteries. Growth is also influenced by growth and sex hormones. Curiously, the latter seems to inhibit activity: cats neutered very early grow slightly longer leg bones. If a bone breaks, bone cells produce new bone to bridge the gap. The cat’s skeleton is a tiny replica of that of the big cats. The vertebrae give great mobility and the forelegs provide superb flexibility. The structure of the wrists allows dexterity in actions such as walking along narrow ledges.

Feline anatomy: Joints

Cats have three different kinds of joints: fibrous, cartilaginous, and synovial. Each has a different level of flexibility and a different function.

  • Fibrous joints: This type of joint has no flexibility at all. The mandible (jawbone), for example, is really made up of two bones with a fibrous joint at the midline. If a cat lands heavily on its jawbone in a fall, this joint may split; so, although the cat may seem to have broken its jaw, it has, in fact, torn this fibrous joint.
  • Cartilaginous joints: Some joints, like the thick discs between the spinal vertebrae, are made from tough cartilage. In cats, these are looser and more supple than similar joints in other species, providing a greater degree of flexibility in the torso. During infancy, the growth plates at the ends of the long bones are temporarily cartilaginous joints, and as such they are less sturdy and more prone to damage than in adulthood.
  • Synovial joints: These are found where the most movement is needed, such as in the legs. They are hinged or ball-and-socket joints, with smooth, articulating cartilage on their contact surfaces, and are surrounded by a joint capsule filled with lubricating synovial fluid. These joints may suffer from excess production of synovial fluid or inflammation due to arthritis or synovitis through injury, disease, or allergy.

Feline anatomy: Ligaments

The tough bands that hold bones together, ligaments, are important in all joints, but vital in synovial joints, which are inherently unstable. The hip joint, in particular, is prone to dislocation.

Skeletal variations and problems

Environmental pressures create natural variations in the cat’s skeleton. In hot climates, cats are naturally small, with a higher surface-area-to-weight ratio, which helps cooling. Cats in cold climates have larger, heavier skeletons. In the wild, severe skeletal anomalies disappear, usually because lethal problems are associated with them. In recent times, active selection for breed standards has led to more dramatic skeletal variations. This has perpetuated the most considerable, and worrying, skeletal problems.

Retractable claws

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Claws grow from the last bone of the toe and are , anchored by tendons. They consist of modified skin: an outer cuticle of hard protein (keratin) protects the dermis, or quick. Cats’ claws are kept sheathed for protection on the move. At rest, ligaments naturally sheath the claws. A cat exposes its claws by contracting digital flexor muscles in its legs, pulling taut the flexor tendons under the paw.

Return from Feline Anatomy – Bones and Joints to Cat Anatomy topics

16.07.2008

Cat Anatomy Heart and Blood Vessels

Author: breeder

Cat Anatomy Heart and Blood Vessels

Cat anatomy – picture of cat’s heart

 picture of cat’s heart

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The Heart and the Blood Vessels

The cat has a comparatively small but exceptionally strong heart. As in all animals the heart is a powerful pump comprising the strongest muscle in the body.

It is surrounded by a serous membrane or sac called the pericardium, which under normal circumstances contains a small quantity of lubricating fluid called the pericardial fluid.

The heart comprises two lower chambers with extremely thick walls (the right and left ventricles) and two upper cavities with slightly thinner walls (the right and left auricles). The left-sided chambers are both larger than the right.

As the blood passes round the body, it collects carbon dioxide from the various tissues and this is carried by the veins to the right auricle.

It then passes through a valved opening into the right ventricle and from there the thick walls pump it to the lungs through the pulmonary artery.

In the lungs the carbon dioxide is expelled as the cat breathes out, and oxygen takes its place as the cat breathes in. The oxygenated blood is then carried back to the left auricle by the pulmonary vein. From there it passes through another valved opening into the left ventricle – the most efficient pumping chamber ever created.

 picture of cat’s heart

The left ventricle pumps the oxygenated blood through the arteries round the entire body (see diagram). The process is continuous, starting when the kitten is in the embryo state within the mother’s womb and stopping only when the cat dies.

Cat Blood Types

Cats have 3 blood types: A, B and AB. Most cats are type A, but incidence of types varies geographically. Virtually all cats in Switzerland are type A, for example, but this drops to 97% in Britain and 85% in France.

Many pedigree breeds are almost exclusively type A, but others show varying levels of type B. Type AB is extremely rare and not linked to breed.

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