Chapter 5

Question 1

Epidermis

Answer 1

Composed of epithelial cells, is the outermost protective shield of the body

Question 2

Dermis

Answer 2

Making up the bulk of the skin, is a tough, leathery layer composed mostly of dense connective tissue. It is vascularized, blood vessels in the dermis diffuse through the tissue fluid on the epidermis. It’s cells are like connective tissue proper: fibroblasts, macrophages, and occasional mast and white blood cells. It’s semifluid matrix binds the body together. Has two layers, the papillary and reticular layers.

Question 3

Subcutaneous tissue

Answer 3

Lies just deep to the skin. Also known as the hypodermis or the superficial fascia bc it is superficial to connective tissue wrapping (fascia) the skeletal muscles. It’s not part of the skin, but it shares functions. Composed of adipose tissue with some areolar connective tissue.

Question 4

Subcutaneous tissue functions

Answer 4

Stores fat, anchors the skin to underlying structures (mostly muscles), slide over structures, shock absorber, and insulator.

Question 5

Cells of the epidermis

Answer 5

Keratinocytes, melanocytes, dendritic cells, and tactile epithelial cells

Question 6

Keratinocytes

Answer 6

Produces keratin, the fibrous protein that gives the epidermis protective properties. Most epidermal cells are keratinocytes. They are tied together by desmosomes and tight junctions to hinder movement of water between cells. They are in the stratum basale. When they reach the surface they are dead.

Question 7

Melanocytes

Answer 7

Spider shaped epithelial cells that synthesize the pigment melanin found in the deepest layer of the epidermis. Made in embrace bound granules called melanosomes and then transferred through cell processes to keratinocytes. The melanin forms a pigment shield on keratinocytes that protects the nucleus from UV radiation.

Question 8

Dendritic cells

Answer 8

Star shaped cells that arose from bone marrow and migrate to the epidermis. Also called Langerhans cells, they ingest foreign substances and a key activators of our immune system. This extends to surrounding keratinocytes

Question 9

Tactile epithelial cells

Answer 9

AKA Merkel cells, are present at the epidermal-dermal junction. Shaped like a spiky hemisphere, each cell is associated with a disc like sensory nerve ending. It serves as a sensory receptor for touch.

Question 10

Layers of the epidermis

Answer 10

Stratum basale, stratum spinosum, stratum granulosum, stratum lucidum, stratum corneum

Question 11

Stratum basale (basal layer)

Answer 11

The deepest epidermal layer, aka stratum germinativum, is attached to underlying dermis. It consists of a single row of stem cells. Has many mitotic nuclei that reflects rapid division of these cells. One daughter cell is pushed into the cell layer above to become a mature keratinocyte. The other remains in the basal layer to continue producing new keratinocytes.

Question 12

Stratum spinosum (prickly layer)

Answer 12

Several layers thick and consist of cells that contain thick bundles of intermediate filaments which consist of tensions-resisting protein, pre-keratin. They are anchored to desmosomes.

Question 13

Stratum granulosum (granular layer)

Answer 13

Thin and consists of one to five cell layers where keratinization (cells fill with keratin) begins. These cells flatten, their nuclei and organelles disintegrate, and they accumulate two types of granules (keratohyaline granules and lamellar granules). Proteins within the keratinocytes and lipids deposited outside them make these cells tough and water resistant.

Question 14

Keratohyaline granules

Answer 14

Help to form keratin in the upper layers

Question 15

Lamellar granules

Answer 15

Contain a water-resistant glycolipid that is secreted in the extracellular space. Together with tight junctions, the glycolipid plays a major part in slowing water loss across the epidermis.

Question 16

Stratum lucidum (clear layer)

Answer 16

Found only in thick skin, is a translucent band just above the stratum granulosum. Consists of a few rows of flat, dead keratinocytes. It’s cells are identical to this of the bottom of the next layer, the stratum corneum.

Question 17

Stratum corneum (horny layer)

Answer 17

Outermost epidermal layer is 20 to 30 cell layers thick that accounts for 3/4s of epidermal thickness. Keratin and proteins that accumulate just inside the plasma membrane of cells in this stratum protect the skin against abrasion and penetration. The glycolipid between layers makes it nearly waterproof. They shed regularly (dandruff).

Question 18

Papillary dermis

Answer 18

Areolar connective tissue in which fine interlacing collagen and elastic fibers form a mat with many blood vessels. The looseness allows phagocytes and other defensive cells to wander as they patrol for bacteria.

Question 19

Dermal papillae

Answer 19

Peglike projections that indent the overlying epidermis. They contain capillary loops and others house free nerve endings (pain receptors) and touch receptors (tactile corpuscles or Meissners corpuscles). In thick skin, they lie atop dermal ridges which cause overlying epidermis to form epidermal ridges. These skin ridges (friction ridges) may enhance grip and sense touch by enhancing vibrations detected by lamellar corpuscles (receptors) in the dermis.

Question 20

Reticular dermis

Answer 20

Coarse, dense irregular connective tissue that is nourished by blood vessels in the dermal vascular plexus which is between this layer and the subcutaneous tissue. The extracellular matrix contains thick bundles of interlacing collagen fibers.

Question 21

Cleavage (tension) lines

Answer 21

Collagen fibers run parallel to the skin surface. Separations, or less dense regions, between these bundles form cleavage lines in the skin. They run longitudinally in the skin of the limbs and in circular patterns around the neck and trunk. Incisions are made parallel to these lines where skin heals more quickly.

Question 22

Flexure lines

Answer 22

Dermal folds that occur at or near joints where the dermis is tightly secured to deeper structures. Since they don’t slide easily, the dermis folds and eep skin creases form. Visible in the wrist, fingers, soles, and toes.

Question 23

Melanin

Answer 23

Polymer made of an amino acid called tyrosine. It can be reddish yellow to brownish black. It depends on an enzyme called tyrosinase. It is transported from melanocytes to the basal keratinocytes. Then, lysosomes break down the melanosomes. Found only in deeper layers of the epidermis.

Question 24

Carotene

Answer 24

Yellow to orange pigment found in certain olla the products such as carrots. It is in the stratum corneum and in the fat of subcutaneous tissue. It can be converted to vitamin A.

Question 25

Alterations in skin color

Answer 25

Blueness (cyanosis) poor oxygen, pallor (blanching) emotional stress cause blood to go to organs, redness (erythema) embarrassment, fever, inflammation, yellowness liver isn’t functioning properly and results in jaundice, red/purple/green/yellow marks bruises are leaking blood vessels, brown or black “necklace” or bruises insulin resistance and elevated blood glucose

Question 26

Hemoglobin

Answer 26

Red pigment found in blood cells circulating through the dermal capillaries that produces the pinkish hue of fair skin.

Question 27

Skin appendages

Answer 27

Hair and hair follicles, nails, sweat glands, and sebaceous (oil) glands. Derive from epithelial cells of the epidermis that extend to the dermis.

Question 28

Hairs

Answer 28

Or pili, are flexible strands produced by hair follicles and consist of largely dead, keratinized cells. The hard keratin has two advantages over soft keratin: (1) it is tougher and more durable (2) it’s individual cells do not flake off

Question 29

Hair types depending on the shaft

Answer 29

Flat and ribbonlike in cross section: kinky, oval: silky and wavy, perfectly round: straight and course.

Question 30

3 concentric layers of keratinized cells

Answer 30

Medulla, cortex, and cuticle

Question 31

Medulla

Answer 31

It’s central core, consists of large cells and air spaces. Only one that contains soft keratin and is absent in fine hairs.

Question 32

Cortex

Answer 32

Bulky layer surrounding the medulla, consists of several layers of flattened cells.

Question 33

Cuticle

Answer 33

Outermost cuticle is formed from a single layer of cells overlapping one another. The most heavily keratinized and provides strength and keeps the inner layers compact. Wears away at the tip of the hair shaft (split ends)

Question 34

Hair pigment

Answer 34

Made by melanocytes at the base of the hair follicle and transferred to cortical cells. Different concentrations create different colors. Red is colored by a related pigment called pheomelanin. When melanin production decreases and air bubbles replace melanin in the hair shaft, hair turns gray or white.

Question 35

Structure of a hair follicle

Answer 35

Hair follicles fold down from the epidermal surface into the dermis. The deep end is 4 mm below the skin surface and expands to form a hair bulb. A knot of sensory nerve endings called a hair follicle receptor, or root hair plexus, wraps around each hair bulb.

Question 36

Hair papilla

Answer 36

Dermal papilla that protrudes into the hair bulb. Contains a knot of capillaries that supplies nutrients to the growing hair and signals it to grow.

Question 37

Peripheral connective tissue sheath (fibrous sheath)

Answer 37

Derived from the dermis and forms the external layer of the follicle wall.

Question 38

Glassy membrane

Answer 38

At the junction of the fibrous sheath and the epithelial root sheath. It’s the basement membrane of the follicle epithelium.

Question 39

Epithelial root sheath

Answer 39

Derived from the epidermis and has two components: the external root sheath, a direct continuation of the epidermis, and the internal root sheath, which is derived from the matrix cells.

Question 40

Hair growth

Answer 40

Cells in the bulb divide rapidly and make up the hair matrix. As the matrix produces new hair cells, the older part of the hair is pushed upward, and it’s fused cells become keratinized and die. Hair matrix cells are replenished by stem cells that migrate down the bulb from a region closer to the skin surface called the hair bulge.

Question 41

Arrector pili

Answer 41

Bundle of smooth muscle cells and is attached in a way that it’s contraction pulls the hair follicle upright and dimples skin causing goosebumps.

Question 42

Vellus hair

Answer 42

Body hair of children and adult females is pale and fine vellus hair

Question 43

Terminal hair

Answer 43

Coarser, longer hair of the eyebrows, eyelashes, and scalp and may be darker. At puberty, they appear in axillary and punic regions of both sexes and on the face and chest of males. This is in response to the stimulating effects of androgens (male sex hormones).

Question 44

Male pattern baldness

Answer 44

Genetically determined, gender influenced condition where follicles respond to androgens with shorter and shorter growth cycles.

Question 45

Sweat glands

Answer 45

Aka sudiferous glands, are distributed over the entire skin except the nipples and parts of the genitalia (up to 3 million per person). Two types: eccrine and appocrine. Myoepethelial cells contract, forcing sweat into the glands duct system to the skin surface.

Question 46

Eccrine sweat glands

Answer 46

Aka merocrine sweat glands, are numerous esepeciaolt on the palms, soles of the feet, and forehead. They are simple, coiled, tubular glands. The secretory part is in the dermis and the duct extends into a funnel shaped pore at the surface. It’s a hypotonic filtrate of the blood that passes through secretory cells and is released by exocytosis. It is 99% water, with some salts, metabolic wastes, and a microbe killing peptide called dermcidin. Sweat is acidic with ph of 4 and 6.

Question 47

Apocrine sweat glands

Answer 47

Confined to the axillary and anogenital areas. They are merocrine glands and release by exocytosis. They are larger and lie deeper in the dermis and their ducts empty into hair follicles. Same as sweat but with fatty substances and protein that is milky and yellowish. Function at puberty under male sex hormones (androgens). Precise function isn’t known. May be equivalent to animals sexual scent gland bc (1) sexual foreplay increase activity (2) enlarge and recede with menstrual cycle (3) secretario a may act as pheromones. Two modified types: ceruminous glands and mammary glands.

Question 48

Ceruminous glands

Answer 48

Found in the lining of the external ear canal. It mixes with sebum to form cerumen, or earwax, that deters bugs and blocks foreign material

Question 49

Mammary glands

Answer 49

Secrete milk and are part of the integumentary system but put with female reproductive organs.