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An in-depth exploration of the skin, its structure, and its functions. Topics include the different layers of the skin (epidermis, dermis, and hypodermis), the role of melanocytes and melanin in skin color, the differences between thick and thin skin, and the functions of various skin glands. Additionally, the document covers the structure and function of hair, including the differences between vellus and terminal hair.
What you will learn
Typology: Study Guides, Projects, Research
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B. The dermis (meaning skin) is a deeper layer of connective tissue.
B. The hypodermis is loose connective tissue containing fat deposits (about half of the body's fat stores).
C. The hypodermis is the site of subcutaneous injections.
Dermis
B. The reticular layer is a fiber network (reticulum) that connects the papillary layer to the hypodermis.
Rupture of the fibers due to overstretching (e.g., pregnancy) produces lines called striae or stretch marks.
Cleavage or tension lines are produced in the skin because of the collagen and elastin fiber orientation.
) Would it be best for surgical incisions to run parallel to cleavage lines or cut across them? Explain.
B. The papillary layer contains blood vessels (blood supply to the epidermis) and sensory receptors.
Epidermis
Stratum granulosum
Stratum lucidum
Stratum corneum
) Scopolamine is a drug used to prevent motion sickness. One method of administering scopolamine is in a skin patch that is attached behind the ear. What properties must scopolamine have in order to diffuse through the skin?
Nucleus
Keratohyalin granules Lamellar body
Protein envelope forms
Lamellar body releases lipids
Keratin Lipids
Protein envelope
Thick and Thin Skin
Skin Color
B. Keratinocytes adjacent to the melanocyte ingest the cell processes of melanocytes containing the melanosomes. Thus, keratinocytes have melanosomes, but do not produce them.
B. The amount of melanin in the skin can be increased by exposure to UV light and by certain hormones (MSH and ACTH).
C. The amount of melanin in the skin is genetically determined. Because the number of melanocytes in the skin is the same for different races, it is the amount and kind of melanin that is responsible for the color of the skin of different races.
B. Increased blood flow causes a red color, as in blushing, anger, fever, overheating, and the inflammatory response.
C. Decreased blood flow causes the skin to appear pale, as in shock, cold, and death.
) Practice Problems A. Explain the difference in skin color between the anterior and posterior surfaces of the forearm.
B. The hair consists of an inner medulla (soft keratin similar to keratin in skin), an outer cortex (hard keratin that makes the hair tougher than the epidermis), and the cuticle (a single layer of overlapping cells that attach to the hair follicle wall).
B. The epithelial root sheath , which is between the dermal root sheath and the hair, has two parts.
The external epithelial root sheath is an extension of the skin epidermis into the dermis.
The internal epithelial root sheath is produced by the matrix,
C. The papilla in the hair bulb contains blood vessels and nerves.
) Why is it important for the papilla to have blood vessels?
Hair Growth
Hair Color
B. Red hair is caused by varying amounts of a red type of melanin.
C. A white hair is hair without melanin. Gray hair is a mixture of unfaded, faded, and white hairs.
) In the movies it is not uncommon to see the hair of a person who has been very frightened turn white in a short period of time. Explain why you believe or disbelieve this.
Muscles
) Why would it be advantageous for hair to "stand on end"? (Hint: think of fur).
Glands
B. Sebaceous glands usually open into a hair follicle.
C. Acne.
At puberty, increased levels of the hormone testosterone cause increased sebum production.
The epidermis of the hair follicle produces many cells.
The sebum and cells plug the hair follicle.
Bacteria grow and a pimple results.
) Why does the pimple get red?
C. The nail rest on the nail bed , the proximal part of which is the nail matrix where the nail is formed. The lunula is the part of the nail matrix that can be seen through the nail.
D. The eponychium (cuticle) is skin that grows onto the base of the nail, and the hyponychium is skin is skin beneath the free edge of the nail.
) In the movies, dead people who have been buried and then dug up are sometime shown to have very long nails. Explain why you believe or disbelieve this.
Protection
B. Prevents the loss of water (lipids in epidermis). Burn patients are given fluid. The larger the burn area, the greater the fluid replacement.
to use the rule of nines (p. 152). Read the Systems Pathology on Burns for your own interest (p. 160).
Sensation
Temperature Regulation.
) Why does your nose turn red in the cold?
Vitamin D Production
UV light Ergosterol Vitamin D 2 Vitamin D 3 precursor (Plants) (Milk, vitamin pills) (Fish, liver, egg yolk)
UV light
Vitamin D 3 precursor Liver
Kidney
Active vitamin D Calcium and phosphate balance
Excretion