Examining The Anatomy Of The Skin Biology Essay


Epidermis - is the outer layer of the skin which contains no nerves or blood supply. Within the epidermis are the squamous cells, which are flat, scalelike and arranged in layers called strata. There are about five different layers of stratified epithelium cells, each having specific functions. The stratum basale(basal layer) is the deepest layer of the epidermis. It is where new cells are constantly being reproduced, hence pushing the older cells toward the outermost surface of the skin. The basal cell layer also contains melanocytes which gives the skin its color and provides protection from the sun's ultraviolet rays. The stratum corneum is the outermost layer of the skin. It is where the dead skin cells are continuously being shed and replaced. Once the cells reach the outermost layer of the epidermis they die and then fill with a hard water repellent protein called keratin. The main characteristic of keratin is waterproofing the body. It creates a barrier so that water does not penetrate the body or is lost from the body - hence it prevents microorganisms from penetrating the unbroken skin. For example, with burns when the skin is injured and the barrier layer is damaged, microorganisms and other contaniments can pass through the epidermis to the lower layers of the skin causing an epidermis infection(s).

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Dermis (corium) - is an inner thick layer of skin located directly beneath the epidermis. It protects the body from natural injury and compression and acts as a storage area for water and electrolytes. Consisting of living tissue, the dermis contains capillaries, lymphatic channels and nerve endings. Also, within the dermis are the hair follicles, sweat glands, and sebaceous(oil) glands. The dermis also has both connective and elastic fibers to give it strength and elasticity. The elastic fibers can be overstretched by pregnancy and obesity causing stretch marks(stria). They appear as pinkish-blue streaks with jagged edges accompanied by itching. Once they heal and lose their color, the stretch marks appear as silvery-white scar lines. The thickness of the dermis varies from the thickness of the palms of your hands and the soles of your feet to the thin layers of your eyelids. The ridge patterns on your fingertips provide the friction for grasping things. The ridges form a pattern which are genetically determined and are the basis of fingerprints and footprints.

Subcutaneous tissue - it consists mostly of loose connective tissue and adipose(fatty) tissue which connects the skin to the surface muscles. It is located beneath the dermis. Occasionally it is called the superficial fascia or subcutaneous fascia. It provides the insulation for the body and protects the deeper tissues. It is abundant in nerves and nerve endings including those which supply the dermis and epidermis. The major blood vessels that supply the skin go through the subcutaneous layer, the sweat glands and the hair root grows from the dermis down into the subcutaneous layer. The thickness of the subcutaneous layer varies from the thickest layer over the abdomen to the thinnest layer over the eyelids.

The Accessory Structures of the skin are the hair, nails, and glands.

A hair strand is a long slender filament of keratin that consists of the hair root, which is embedded in the hair follicle and a hair shaft (visible part of the hair). Each strand develops in the hair follicle, with the new hair developing from the keratin cells located at the bottom of the follicles. The human body is covered by hair except for the palms of your hands, the soles of your feet, the lips, the nipples and some areas of the genitalia. By the end of the second trimester of pregnancy, the fetus is covered by soft downy hair called lanugo. This hairy covering is almost gone by birth, with the remaining lanugo gone soon after birth. Melanocytes provide the hair's color, the dark pigmented cells wraparound the core of the hair shaft. Melanin which is produced by these cells gives the hair a black or brown color according to the amount of cells produced. Red hair is produced by a unique type of melanin. Usually due to the aging process and when the amount of melanin in the hair decreases significantly the hair turns gray or white. The fingernails and toenails are protective coverings for the tips of the fingers and toes. Covered by hard keratinized nail beds are the dorsal surface of the last bone of each finger or toe. The visible part of the nail is the nail body. The fold of the skin at the base of the nail body is the cuticle. The extension of the nail body beneath the cuticle is the root of the nail. At the base of the nail body nearest the root is a crescent - shaped white area called the lunula. The free edge of the nail extends beyond the tip of the finger tip or toe. Nail growth is about 0.5 mm per week. An epithelial layer located right beneath the nail bed nourishes the nail body. The abundant supply of blood vessels contained in the nail gives the pink color of the nails we see.

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The sweat or sudoriferous gland is deep within the dermis and ends up at the surface of the skin through a tiny opening called a pore. The sweat glands are found on most of the body surfaces especially the palms of the hands, the soles of the feet, the forehead, and the armpits. The two main functions of the sweat glands are to cool the body by evaporation and to eliminate waste products through the pores. The sweat glands produce a clear watery fluid known as perspiration (sweat). Sweat is odorless. When it comes in contact with the bacteria on the skin it becomes contaminated and decomposes resulting in the odor associated with sweating . The sebaceous gland( oil gland), secretes sebrum which lubricates the hair and keeps the skin soft and waterproof. It is secreted along the shaft of the hair follicles and onto the skin through ducts which open directly onto the epidermis. Influenced by the sex hormones the secretion of sebrum increases during adolescence. In some cases pimples or blackheads may develop because the sebaceous gland ducts become blocked due to an increase secretion of sebrum. Sebaceous glands are numerous on the chin, the face, the scalp, and the forehead. They are not on the hands and feet. The ceruminous gland is a modified sweat gland. It is found on the surface of the external ear canal, it lubricates the skin of the ear with a yellowish brown waxy substance called cerumen (ear wax).

Chapter 6

Name and briefly describe 15 different bones with a definition for each.

humerus - is the upper arm bone. It joins the scapula above and the radius and ulna below.

radius - is one of the two lower arm bones that joins the humerus above and the wrists bones below. It is on the lateral, or thumb side of the arm.

ulna - is the second of the two lower arm bones that joins the humerus above and the wrist bones below. The ulna has a large projection at its end called the olecranon process. It is the olecranon that forms the point of the elbow.

carpals - the bones of the wrist. Each wrist has eight carpal bones (two rows of four bones each).

metacarpals - they form the bones of the hand. Metacarpals means "beyond the carpals." The metacarpals join with the carpals at their upper(proximal) end, and with the phalanges (fingers) at their lower (distal) end.

phalanges- the bones of the fingers and toes. Each finger has three phalangeal bones. The thumb has two.

pelvis- is the bony structure formed by the hip bones (ilium, ischium, and pubis), the sacrum, and the coccyx. It is the lower part of the trunk of the body and acts as a support for the vertebral column and as a connection to the lower extremities.

pelvic girdle- is the bony ring formed by the hip bones, the sacrum, and the coccyx the ring that forms the wall of the pelvis.

femur- is the thigh bone. It is the longest, heaviest and strongest bone in the body.

patella- is the knee bone, or kneecap. It is the largest sesamoid bone in the body.

tibia- is the larger and stronger of the two lower leg bones . Also, called the shin bone. The tibia is located on the great toe side of the lower leg. Located down the center front of your lower leg.

fibula- is the more slender of the two lower leg bones and is lateral to the tibia.

tarsals- all bones of the ankle. There are seven tarsal bones.

calcaneus- is the heel bone, acts as a point of attachment for several of the muscles of the calf.

talus bone- joins with the tibia and the fibula to form the ankle joint. The impact of one's entire body weight is on the talus bone at the point of this connection and is evenly distributed to the other tarsal bones. The posterior part of the foot consisting of the talus and the calcaneus is called the hind foot.

Cite the classification of fractures (10) including definition of each. Explain in general the treatment for fractures

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Fracture- is a broken bone, a sudden breaking of a bone. Fractures are classified according to the severity of the break.

closed reduction(simple fracture) - there is a break in a bone, but no open wound in the skin.

open fracture (compound fracture)- there is a break in a bone, as well as an open wound in the skin. complete fracture- is a break that extends through the entire thickness of the bone.

greenstick fracture (incomplete fracture)- it is a break that does not extend through the entire thickness of the bone; that is, one side of the bone is broken and one side of the bone is bent. The incomplete fracture has the name greenstick fracture because its break is similar to trying to snap a "green stick or branch" from a tree. The break is incomplete, with one side breaking and the other side bending considerably but not breaking.

compression fracture- is caused by bony surfaces being forced against each other, as in the compression of one vertebrae against another. Compression fractures are often associated with osteoporosis.

impacted fracture- occurs when a direct force causes the bone to break, forcing the broken end of the smaller bone into the broken end of the larger one.

comminuted fracture- occurs when the force is so great that it splinters or crushes a segment of the bone.

Colles' fracture - occurs at the lower end of the radius, within 1 inch of connecting with the wrist bones.

hairline fracture(stress fracture)- it is a minor fracture in which the bone continues to be in perfect alignment. The fracture appears on x-ray as a very thin "hairline" between the two segments. It does not extend through the entire surface of the bone. Usually the hairline fracture is not visible on x-ray until three to four weeks after the onset of symptoms.

pathological fracture- occurs when a bone, which is weakened by a preexisting disease, breaks in response to a force that would not cause a normal bone to break. Examples of causes for pathological fractures include but not limited to rickets, osteomalacia, and osteoporosis.

occult fracture- is a fracture that cannot be detected by x-ray until several weeks after the injury a( "hidden" fracture). One will experience pain and swelling. This type of fracture is likely to occur in the ribs, the tibia, the metatarsals, or the navicular bones(small ones in the hand and foot).

Treatment of Fractures -

closed reduction- consists of aligning the bone fragments through manual manipulation or traction without surgery. Once the fracture is reduced, the bone is immobilized to maintain the bone's position until it heals. The immobilization devices used are a cast, splint or immobilizer. They protect the realignment and give support. It also reduces the pain. With casting and splinting it is important to check for swelling and loss of sensation.open reduction- consists of realigning the bone under direct observation during surgery. Internal fixation devices such as screws, pins, wires, and nails may be used to internally keep the bone alignment in place while the healing takes place. It is common for these devices to be used with fractures of the femur and fractures of the joints.

Chapter 7

The body contains three types of muscles: skeletal muscle, smooth muscle, and cardiac muscle.

skeletal muscle(voluntary muscles) - attaches to the bones of the skeleton. They operate under conscious control. All voluntary muscles are not skeletal muscles. Some voluntary muscles are not attached to the skeleton. These muscles provide the movements of the face, eyes, tongue, and pharynx. When viewed under the microscope this muscle has a striped appearance, they are also known as striated muscles. Working in pairs the skeletal muscles coordinate their movement through the opposing actions of contraction and relaxation.

smooth muscle(visceral muscle)- are found in the hollow organs and tubes such as the stomach, respiratory passageways, intestines, and blood vessels. Smooth muscles are not striated when viewed under a microscope. They are not under individual conscious control. They are known as involuntary muscles. The contraction of smooth muscle is controlled by hormones, and the autonomic nervous system. The autonomic nervous system regulates the activity of the cardiac muscle, the smooth muscle, and the glands.

cardiac muscle- is a specialized type of muscle that forms the wall of the heart. It is controlled by the autonomic nervous system and is an involuntary muscle. Viewed under the microscope, the cardiac muscle appears striated.


fibrous joint - in a fibrous joint, the surface of the bones fit closely together and are held together by fibrous connective tissue(ex: suture between theskull bones).

cartilaginous joint - in a cartilaginous joint, the bones are connected by cartilage - as in the synphysis (joint between the pubic bones of the pelvis). This type of joint allows for limited movement.

synovial joint - the bones have a space between them called the joint cavity. It is lined with a synovial membrane, which secretes a thick lubricating fluid called synovial fluid. The bones are held together by ligaments. The surfaces of the connecting bones are protected by a thin layer of cartilage. This joint allows free movement. The function of the joints: hinge joint allows movement in one direction - a back and forth motion. The ball-and-socket joint allows for movement in many directions around a central point. Ex: the shoulder joint and hip joint. Movement of joints: 1. flexion - is a bending motion. It decreases the angle between two bones., 2. extension - is a straightening motion. It increases the angle between two bones., 3. abduction - is the movement of a bone away from the midline of the body., 4. adduction- is the movement of a bone toward the midline of the body., 5. rotation - is the movement that involves the turning of a bone on its axis., 6. supination - is the act of turning the palm up and forward.,7. pronation - is the act of turning the palm down or backward., 8. dorsification of the foot narrows the angle between the leg and the top of the foot., 9. plantar flexion of the foot increases the angle between the leg and the top of the foot., 10. circumduction- is the movement of an extremity around in a circular motion.