Skin Function. What is it?

The skin is the largest organ of our body and one of the 7 channels of elimination containing about 70% water, 25% protein and 2% lipids, the skin helps the main organs of elimination (liver, kidneys, intestines) get rid of waste buildup.

The uppermost layer of the skin is called epidermis. The deeper layer is called the dermis, which contains collagen and elastin ( keep the skin flexible and firm). The dermis also contains sebaceous glands, sweat glands, lymph vessels, hair follicles and nerves. Beneath the dermis lies a tissue of fat cells. Infection can occur when the exfoliation process ( the renewal of cells when they shed to make room for new ones) slows down and your skin pores get blocked.

The Skin has five main functions :

 

1.It acts as a mechanical barrier to infections. It ultimately prevents microorganisms and other substances from entering the body. Langerhans cells (a type of macrophage) are found within the dermis, they engulf invaders foreign to the body and debris. Keratin layers in the epidermis together with sebum produced by sebaceous glands act as a waterproof barrier. Melanocytes protect the body from ultraviolet light.Finger and toenails protect the extremities of fingers and toes from damage. Fingertips are important for dexterity and the sense of touch; they have ridged areas to assist in picking things up.Hair follicles offer some extra protection to certain parts of the body such as eyes and head.

2. Skin provides the sense of touch or sensation we need to know more about our outside environment through recognizing heat, cold, pain and other sensations. Nerve endings of the skin provide the body with a great deal of information about the outside environment.

3. It regulates body temperature. Considerable heat is lost through the skin. Even under extreme conditions of high temperature and exercise, our skin tends to make body temperature normal. The production (evaporation) of sweat in the skin cools us down when exposed to too much heat.

The core body temperature needs to be kept constant for normal physiological activity to take place (370c). It needs to maintain a core temperature for homeostasis.

4. Skin excretes waste product and excess salt from the body. Sweat includes waste products in solution. Water is lost continuously through the skin as insensible sweating. More pronounced water loss through sweating occurs as part of temperature regulation.

5. Skin synthesizes the use of Vitamin D in the presence of sunlight and ultra violet radiation needed for the absorption of calcium and phosphate.

M U S C U L A R S Y S T E M

C O N T E N T S :

The human body contains more than 650 individual muscles which are attached to the skeleton, which provides the pulling power for us to move around. The main job of the muscular system is to provide movement for the body. The muscular system consist of three different types of muscle tissues : skeletal, cardiac, smooth. Each of these different tissues has the ability to contract, which then allows body movements and functions. There are two types of muscles in the system and they are the involuntary muscles, and the voluntary muscles. The muscle in which we are allow to control by ourselves are called the voluntary muscles and the ones we can? control are the involuntary muscles. The heart, or the cardiac muscle, is an example of involuntary muscle.

Front muscles

CARDIAC MUSCLE:

The cardiac muscles is the muscle of the brain itself. The cardiac muscle is the tissue that makes up the wall of the heart called the mydocardium. Also like the skeletal muscles, the cardiac muscle is striated and contracts through the sliding filament method. However it is different from other types of muscles because it forms branching fibers. Unlike the skeletal muscles, the cardiac muscle is attached together instead of been attach to a bone.

SKELETAL MUSCLE:

The skeletal muscle makes up about 40 % of an adults body weight. It has stripe-like markings, or striations. The skeletal muscles is composed of long muscle fibers. Each of these muscles fiber is a cell which contains several nuclei. The nervous system controls the contraction of the muscle. Many of the skeletal muscle contractions are automatic. However we still can control the action of the skeletal muscle. And it is because of this reason that the skeletal muscle is also called voluntary muscle.

SMOOTH MUSCLE:

Much of our internal organs is made up of smooth muscles. They are found in the urinary bladder, gallbladder, arteries, and veins. Also the digestive tract is made up of smooth muscle as well. The smooth muscles are controlled by the nervous system and hormones. We cannot consciously control the smooth muscle that is why they are often called involuntary muscles.

Back muscles

Skeletal muscle

Skeletal muscle

Skeletal muscle fibres are multinucleated cells, with the nuclei situated immediately beneath the sarcolemma (cell membrane). An individual fibre may be up to 35cm long. A mature skeletal muscle fibre is composed of a large number parallel running myofibrils. The myofibrils in turns consist of overlapping parallel-arranged thin actin filaments and thick myosin filaments. The filaments are anchored to specific accessory proteins. The functional unit of the fibril is the sarcomere, which is situated between two Z-lines.

A thin layer of connective tissue, the endomysium, surrounds each muscle fibre. Several muscle fibres are bundled together as a fasciculus (Pl fasciculi). The connective tissue layer surrounding the fasciculi is known as the perimysium. An individual muscle is a number of fasciculi enclosed by the epimysium, a thick dense connective tissue capsule. The connective tissue framework is continuous with that of the tendons and muscle attachments to direct the muscle forces to the bone, skin, etc.

Muscles are highly vascular with the blood vessels running in the various connective tissue layers. The different fibre types may histologically visualized by the use of histochemical techniques.  Skeletal muscle contraction is regulated by intracellular calcium stored in the T-tubule system.