Chpt 5. Integumentary System (midterm)

o The dermis is divided into 2 layers:

1) papillary layer -- superficial 2) reticular layer -- deep o The papillary layer derives its name from projections, called dermal papillae. That extended toward the epidermis. o The papillary layer is loose connective tissue with thin fibers that are somewhat loosely arranged. o The papillary layer also contains blood vessels that supply the overlying epidermis with oxygen & nutrients, remove waste products, & aid in regulating body temperature.

Hair Muscles:

Associated with each hair follicle are smooth muscles called the arrector pili, which extends from the dermal root sheath of the hair follicle to the papillary layer of the dermis. Normally the hair follicle & the hair inside it are at an oblique angel to the surface of the skin. When the arrector pili muscles contract, they pull the follicle into a more perpendicular position, causing hair to "stand on end". Movement of the hair follicles produce raised areas called, "goose bumps".

Terminal Hair:

At puberty, terminal hair, especially in the pubic & axillary regions replace much of the vellus hair. The hair of the chest, legs, & arms is approximately 90% terminal hairs in males. Approximately 35% in females. In males terminal hairs replace the vellus hairs of the face to form the beard. The beard, pubic, & axillary hairs are signs of sexual maturity. In addition, pubic & axillary hair may function as wicks for dispersing odors produced by secretions from specialized glands in the pubic & axillary regions. It has also has been suggested that pubic hair reduces friction when the arms move.

Other glands:

Other skin glands are the ceruminous glands & the mammary glands.

Stratum corneum, eponychium, & hyponychium

Pg. 152-153 The stratum corneum of the nail fold grows onto the new body as the cuticle or upon Eponychium.I need the free edge of the new body is the hyponychium, A thickened region of the stratum cornermen.

Hair:

The presence of hair is one of the characteristics of all mammals; if the hair is dense & covers most of the body surface, it is called fur. In humans, hair is found everywhere on the skin except the palms, soles, lips, nipples, & external genitalia, and distal segments of the fingers & toes. By 5th/6th month of fetal development, delicate, unpigmented hair called lanugo has developed & covered the fetus. Near the time of birth, terminal hairs, which are long, coarse, & pigmented, replace the lanugo of the scalp, eyelids, & eyebrows.

Pg. 155

Vitamin D synthesis begins in skin exposed ultraviolet light, and people can produce all vitamin D they require by this process if enough UV light is available. However because people live indoors and wear clothing, their exposure to UV light may not be adequate for the manufacture of sufficient vitamin D. This is especially likely for people living in cold climates because they remain indoors or are covered by warm clothing when outdoors. Fortunately vitamin D can also be interested in absorbed in the small intestine. Natural sources of vitamin D or liver especially fish liver, egg yolks, and dairy products such as butter cheese and milk. In addition the diet can be supplemented with vitamin D in fortified milk or vitamin pills. Vitamin D synthesis begins when the precursor molecule 7-dehyrocholesterol is exposed to ultraviolet light and converted into cholecalciferol. Cholecalciferol is released into the blood and modified by hydroxylation, which is hydroxide ions are added, in the liver and kidneys deform active vitamin D, calcitriol.

Subcutaneous tissue:

"Hypodermis" layer of loose connective tissue. Not part of skin or integumentary system, but it does connect the skin to underlying muscle or bone.

Strata:

(Bottom to top) -Stratum Basale (stratum germinativum) -Stratum spinosum -stratum granulosum -stratum lucidum -stratum corneum

Glands:

- Sebaceous glands: produce sebum, which oils hair & surface of skin. -Eccrine sweat glands: produce sweat, which cools the body. -Apocrine sweat glands: produce an organic secretion that can be broken down by bacteria to cause body odor. -Other skin glands: **Ceruminous glands: make cerumen (earwax) **Mammary glands: makes milk

Vitamin D Production:

1) skin exposed to UV light produces cholecalciferol, which is modified in the liver & then in the kidneys to form active vitamin D. 2) Vitamin D increases blood calcium levels by promoting calcium uptake from the small intestine, calcium release from bone, & the reductions of calcium loss from the kidneys.

Stratum Granulosum

2-5 layers of flattened, diamond shaped cells with long axes that are oriented parallel to the surface of the skin. -The name stratum granulosum comes from the presence of nonmembrane bound protein granules of "Keratohyalin". -Keratohyalin accumulates in the cytoplasm of the cell. The lamellar bodies, formed as the cells pass through the stratum spinosum, move to the plasma membrane & release their lipid contents into the extracellular space. Inside the cell, a protein envelope forms beneath the plasma membrane. - In the most superficial layers of the stratum granulosum, the nucleus & other organelles degenerate & the cells die. -However, keratin fibers and Keratohyaline granules within the cytoplasm do not degenerate.

Keratinocytes:

Produce protein called "Keratin", making cells more durable. -give the epidermis the ability to resist abrasion & reduce water loss. - produced when keratinocytes stem cells undergo mitosis in the deepest layer of epidermis. Older cells push to surface & slough off.

Melanocytes:

found in epidermis. -contribute to skin color.

Dermis tissue:

layer of connective tissue. Function: structure strength of skin. rests on sub. cut.

Mammary glands:

modified apocrine sweat glands located in the breasts. They produce milk. The structure and regulation of memory glands are discussed in chapters 28 and 29.

Ceruminous glands:

modified eccrine sweat glands located in the ear canal, external auditory canal. Cerumen or earwax, is composed of the combined secretions of ceruminous and sebaceous glands. Cerumen and hairs in the ear canal protect the tympanic membrane by preventing the entry of dirt and a small insects. However an accumulation of cerumen can block the ear canal and making hearing more difficult.

Eccrine Sweat glands:

o Merocrine sweat glands o Are the most common type of sweat gland. o Simple, coiled, tubular glands that open directly onto the surface of the skin through sweat pores. o Eccrine sweat glands can be divided into 2 parts: Deep, coiled portion, which is mostly into the dermis & the duct, which passes to the skin surface. The coiled part of the gland produces an isotonic fluid that is mostly water, but also contains some salts (sodium chloride mostly) & small amounts of ammonia, urea, uric acid & lactic acid. As the fluid moves through the duct, sodium chloride moves by active transport from the duct back into the body, there by conserving salts. The resulting hyposmotic fluid that leaves the duct is called sweat. When the body temperature starts to rise above normal, the sweat glands produce sweat, which evaporates and cools the body. Sweat also can be released into the palms, souls, and axillae as a result of emotional stress. Emotional sweating is used in light detector (polygraph) tests because sweat gland activity may increase when a person tells a lie. Such tests can detect the sweat produced, even in small amounts, because the salt solution conducts electricity and lowers the electrical resistance of the skin. Eccrine sweat glands are most numerous in the palms of the hands and soles of the feet but are absent from the margin of the lips,the labia minora , and at the tips of the penis and clitoris.

Melanosomes:

o The goli apparatuses of the melanocytes package melanin into vesicles called melanosomes, which move into the cell processes of the melanocytes. Keratinocytes phagocytize the tips of the melanocyte cell processes, thereby acquiring melanosomes. Although all keratinocytes can contain melanin, only the melanocytes produce it.

Langerhans Cells:

part of the immune system.

Apocrine Sweat Glands. pg. 153

simple, coiled, tubular glands that usually open into hair follicles superficial to the opening of the sebaceous glands. April crying so it glands are found in the axillae and genitalia (scrotum and labia majora) and around the anus. They do not help regulate temperature in humans. Apocrine sweat glands become active at puberty as a result of sex hormones. Their secretions contain organic substances, such as 3-methyl-2-hexenoic acid, that are sensually odorless when first released but I quickly metabolized by bacteria to cause what is commonly known as body odor. many mammals use send as a means of communication, and physiologists have suggested that the activity of apocrine sweat glands may signal sexual maturity.

Merkel Cells:

specialized epidermal cells associated with nerve endings responsible for detecting light touch & superficial pressure.

Epidermis tissue:

superficial layer of the skin. - epithelial tissue Function: Resist abrasion, reduce water loss through skin. rests on dermis.

Changes the integumentary system undergoes with age.

the number of functioning melanocytes generally decreases, however in some localized areas, especially on the hands and face, melanocytes increase in number, producing age spots. Age spots are different from freckles which are caused by an increase in melanin production, not an increase in melanocyte numbers. White or gray hairs also appear because of a decrease in or lack of melanin production. pg. 158

Sweat glands/Sudoriferous glands: *Two types of sweat glands:

• Eccrine glands • Apocrine glands Physiologists believed that secretions were released in a merocrine fashion from eccrine glands & in an apocrine fashion from apocrine glands. But we know now that apocrine sweat glands also release some of their secretions in a merocrine fashion & possibly some in a halocrine fashion. Traditionally, they are still referred to as apocrine sweat glands.

Vellus Hairs:

• Short, fine, & usually unpigmented, replace the lanugo on the rest of the body.