Human Anatomy Exam 1 (Ch. 5)

Which covers the entire body, called the integument (covering), would fall prey to harmful bacteria and perish from water and heat loss without it, and is the largest organ of the body?

skin

What are the two layers that the skin is composed of?

epidermis and dermis

What is the epidermis?

composed of epithelial cells (avascular), and is the outermost protective shield of the body

What is the dermis?

makes up the bulk of the skin, and is a tough, leathery layer composed mostly of dense connective tissue, only this is vascularized

Nutrients reach the ______ by diffusing through the tissue fluid from blood vessels in the dermis

epidermis

What is the subcutaneous tissue (hypodermis/superficial fascia)?

lies just deep to the skin (under dermis), superficial to the tough connective tissue wrapping (fascia) of the skeletal muscles, not part of the skin, but shares some of the skin’s protective functions

Which consists mostly of adipose tissue with some areolar connective tissue that absorbs shock and insulator that reduces heat loss and stores fat?

subcutaneous tissue/hypodermis/superficial fasica

the _______ tissue anchors the skin to the underlying structures (mostly muscles), but loosely enough that the skin can slide relatively freely over those structures

subcutaneous

What is fascia?

fibrous membrane covering, supporting, and separating muscles

What are the cells that populate the epidermis?

keratinocytes, melanocytes, dendritic cells, and tactile epithelial cells

What is the main role of keratinocytes?

produce keratin, the fibrous protein that helps give the epidermis its protective properties

______ are tied together by desmosomes for strength and, in some layers, by tight junctions to hinder movement of water between cells

keratinocytes

Keratinocytes arise in the deepest part of the epidermis from a cell layer called the ______ ______

stratum basale

What are melanocytes?

spider-shaped epithelial cells that synthesize melanin, found in the deepest layer of the epidermis

_____ is made in membrane bound granules called melanosomes and then transferred through the cell processes to nearby keratinocytes

melanocytes

Which forms a pigment shield that protects the nucleus from the damaging effects of ultraviolet (UV) radiation in sunlight?

melanin clusters of the superficial, or “sunny” side of the keratinocyte nucleus

Which cells arise from bone marrow and migrate to the epidermis, also called langerhans cells as they ingest foreign substances and are key activators of our immune system?

dendritic

The dendritic cells' slender processes extend among the surrounding keratinocytes, forming what?

a more or less continuous network

What are tactile epithelial cells?

present at the epidermal-dermal junction, each epithelial cells is associated with a disclike sensory nerve ending, combination functions as a sensory receptor for touch

Which skin covers areas subject to abrasion, the palms, fingertips, and soles of the foot?

thick

The epidermis of ______ ______ consists of five layers, or stata, these layers are stratum basale, spinosum, granulosum, lucidum, and corneum

thick skin

Which skin covers the rest of the body, however, stratum lucidum is absent and all of the other strata are thinner? (4 layers)

thin

Which stratum is the deepest epidermal layer, also called stratum germinativum?

basale

The ______ ______ consists of a single row of stem cells, a continually renewing cell population, representing the young keratinocytes?

stratum basale

In stratum basale, the many ______ nuclei seen in this layer reflect the rapid division of these cells

mitotic

What happens each time the basal cells in stratum basale divides?

one daughter cell is pushed into the cell layer just above to begin its specialization into a mature keratinocyte, dies as it moves toward surface, takes 25-45 days

In stratum basale, what happens to the other daughter cell that remains in the basal layer?

continues the process of producing new keratinocytes

How many of the cells in the stratum basale are melanocytes?

10-25%

What is the stratum spinosum (prickly layer)?

several cell layers thick (before basale),

Which stratum are artifacts created during tissue preparation because the cells shrink while holding tight at their many desmosomes, which makes them look like tiny versions of the spiked iron balls from medieval times?

spinosum

Which stratum do the cells contain thick bundles of intermediate filaments, which consist of a tension-resisting protein, pre-keratin, and these filaments resist tension in the cell and are anchored to the desmosomes?

spinosum

Scattered among the keratinocytes are ______ cells, which are most abundant in this epidermal layer

dendritic (melanin granules and dendritic cells are most abundant in this layer)

Which stratum is thin and consists of one to five cell layers in which keratinocyte appearance changes drastically, and the process of keratinization (in which the cells fill with keratin) begins?

granulosum

For stratum granulosum, what happens during the process of keratinization?

the cells flatten, their nuclei and organelles begin to disintegrate, and they accumulate two types of granules; keratohyaline and lamellar granules

What does keratohyaline granules do in the stratum granulosum?

help to form keratin in the upper layers

What does lamellar granules do in the stratum granulosum?

• contain a water resistant glycolipid that is secreted into the extracellular space

• together with tight junctions, the glycolipid plays a major part in slowing water loss across the epidermis

Above the stratum granulosum, what happens to the epidermal cells?

they are too far from the dermal capillaries to survive, the glycolipids coating their external surface cut them off from nutrients, making them die

Which stratum is found only in thick skin, and is visible through a light microscope as a thin translucent band just above the stratum granulosum?

lucidum (clear layer)

Which stratum consists of a few rows of flat, dead keratinocytes, and electron microscopy reveals that its cells are identical to those at the bottom of the nect layer, stratum corneum?

stratum lucidum

An abrupt transition occurs between the nucleated cells of the stratum _______ and the flattened, anucleate cells of the stratum ________

granulosum, corneum

Which stratum is the thickest layer, broad zone of 20-30 cell layers thick that accounts for up to three-quarters of the epidermal thickness, consists rows of dead, flat, anucleate keratinized membranous sacs?

corneum (these cells are the dandruff shed from the scalp and flakes that come off the body)

In the stratum corneum, ______ and ______ that accumulate just inside the plasma membrane of cells protect the skin against abrasion and penetration (barrier against biological, chemical, and physical assaults)

keratin, proteins

In stratum corneum, the ______ between its cells helps keep this layer nearly waterproof

glycolipid

What is the dermis?

made up of strong, flexible connective tissue, supports the epidermis, and binds epidermis and hypodermis

What contains blood vessels, hair follicles, nerves, and glands?

the dermis

What are the two layers that the dermis has?

papillary and reticular, which lie next to one another along an indistinct boundary

What is the papillary dermis?

areolar connective tissue in which fine interlacing collagen and elastic fibers form a loosely woven mat with many small blood vessels (fibroblasts, mast cells, macrophages)

What is the dermal papullae?

peglike projections from the papillary dermis surface indent the underlying epidermis, many contain capillary loops, while others house free nerve endings (pain receptors) and touch receptors called tactile corpuscles or Meissner’s corpuscles, sensitive to light touch

What are the dermal ridges?

found under dermal papillae in thick skin and create epidermal ridges

What are friction ridges?

epidermal + dermal ridges, contribute to our sense of touch by enhancing vibrations detected by the large lamellar corpuscles (receptors) in the dermis, fingertips leave identifying films of sweat called fingerprints on anything we touch because sweat pores open along the patterns of these ridges

What is the reticular dermis?

accounts for about 80% of the thickness of the dermis, which is coarse dense irregular connective tissue

Which dermis does the network of blood vessels that nourishes this layer, the dermal vascular plexus, lies between this layer and the subcutaneous tissue?

reticular

The extracellular matrix of the _____ _____ contains thick bundles of interlacing collagen fibers, which provide strength and resiliency

reticular dermis

What are cleavage (tension) lines?

externally invisible lines tend to run longitudinally in the skin of the limbs and in circular patterns around the neck and trunk (separations between collagen fibers)

What are flexure lines?

dermal folds that occur at or near joints, where the dermis is tightly secured to deeper structures

Which pigments contribute to skin color?

melanin, hemoglobin, and carotene

What is melanin?

polymer made of an amino acid called tyrosine, range in color from reddish yellow to brownish black, transported from melanocytes to the basal keratinocytes and eventually lysosomes break down the melaninosomes, so melanin pigment is found only in the deeper layers of the epidermis (only pigment produced by the skin)

What is carotene?

yellow to orange pigment found in certain plant products such as carrots, tends to accumulate in the stratum corneum and in the fat of the subcutaneous tissue, can be converted to vitamin A, which is essential for normal vision, as well as for epidermal health

What is hemoglobin?

the pinkish hue of fair skin reflects the crimson color of this oxygenated pigment in the red blood cells circulating through the dermal capillaries, oxyhemoglobin in erythrocytes

Number of ______ per unit area is not influenced by gender or race, the differences in skin color may be related to the number of melanin granules in keratinocytes

melanocytes

When we expose our skin to sunlight, ______ secrete chemicals that stimulate melanocytes

keratinocytes

How does “tanning” work?

darkening of preexisting melanin and increase in rate of release, increased rate of synthesis, melanin synthesis by melanocytes is severely reduced or absent

What do the skin appendages include?

hair and hair follicles, nails, sweat glands, and sebaceous (oil) glands, although they all derive from the epidermis, they all extend to the dermis

What are hairs or pili?

flexible strands produced by hair follicles and consist largely of dead, keratinized cels

The hard keratin that dominates hairs and nails have two advantages over the soft keratin found in typical epidermal cells. What are they?

• tougher and more durable

• its individual cells do not flake off

What are the functions of hair?

• warn of insects on skin

• hair on head protects against physical trauma, heat loss, and sunlight

• eyelashes shield eyes

• nose hairs filter

What are the chief regions of the hair?

• root, embedded in the skin

• shaft, projects above the skins surface

What are the three concentric layers of keratinized cells a hair has?

medulla, cortex, and cuticle

What is medulla?

at central core, consists of large cells and air spaces, only part of the hair that contains soft keratin which is absent in fine hairs

What is the cortex?

bulky layer surrounding the medulla, consists of several layers of flattened cells

What is cuticle?

outermost layer, formed from a single layer of cells overlapping one another like shingles on a roof, helps separate neighboring hairs so the hairs does not mat, most keratinized part of hair, provides strength and keeping inner layers tightly compacted

Which is subjected to the most abrasion, causing to wear away at the tip of the hair shaft then allowing keratin fibrils in the cortex and medulla to frizz, causing split ends?

cuticle

What are hair follicles?

fold down from the epidermal surface into the dermis, sometimes subcutaneous tissue, has two layered wall; part dermis, part epidermis

The deep end of the follicle expands to form a ____ ____

hair bulb

Which knot of sensory nerve endings wraps around each hair bulb?

hair follicle receptor/root hair plexus

What is the hair papilla?

dermal papilla that protrudes into the hair bulb, containing a knot of capillaries that supplies nutrients to the growing hair and signals it to grow, if destroyed by trauma, follicle permanently stops producing hair, provides blood supply

What is the peripheral connective tissue sheath?

derived from the dermis, forms external layer of the follicle wall

What is the glassy membrane?

at the junction of the fibrous sheath and the epithelial root sheath, is the basement membrane of the follicle epithelium

What is the epithelial root sheath?

• derived from epidermis

• has two components

  • external root sheath: direct continuation of the epidermis (stratified squamous invaginates deep)

  • internal root sheath: derived from the matrix cells (hair matrix cells are your reproductive cells, cells that build your hair)

What is the hair matrix?

dividing cells (hair grows because cells in the bulb of the follicle divide rapidly), lie immediately adjacent to the hair papilla

Arrector pili muscle causes?

goose bumps, smooth muscle attached to follicle

What are nails?

forms a clear protective covering on the dorsal surface of the distal part of a finger or toe, contain hard keratin, each has a proximal root (embedded in skin), a nail plate or body, and a free edge

The nail rests on a bed of epidermis called the ____ ____. This bed only contains the deeper layers of the epidermis because the nail itself corresponds to the superficial keratinized layers

nail bed

What is the nail matrix?

thickened proximal portion of the nail bed, responsible for nail growth, as nails cells produced by matrix become heavily keratinized, the nail body slides distally over nail bed

What are sweat glands (sudiroferous glands)?

distributed over the entire skin expect nipples and parts of the external genitalia

What are the two types of sweat glands?

eccrine and apocrine

What are the eccrine sweat glands (merocrine sweat glands)?

far more numerous than apocrine sweat glands and are particularly abundant on the palms, soles of the foot, and forehead, each is simple, coiled, tubular gland, secretory part lies coiled in the dermis and the duct extends to open in a pore at the skin surface, functions for thermoregulation, functions throughout life,

What is the hypotonic filtrate of the blood that passes through the secretory cells of the sweat glands and is released by exocytosis?

eccrine gland secretion/sweat, 99% water with some salts (mostly sodium chloride), traces of metabolic wastes (urea, uric acid, ammonia), and a microbe-killing peptide called dermcidin

What is sweating’s major role?

prevent the body from overheating

What are apocrine sweat glands?

largely confined to the axillary and anogenital areas, they are merocrine glands which release their product by exocytosis like the eccrine sweat glands, stinky sweat is due to bacterial action

What does apocrine secretion contain?

same components as basic sweat, plus fatty substances and proteins, it is viscous and sometimes has a milky or yellowish color

When does apocrine glands begin functioning?

at puberty under the influence of male sex hormones (androgens) and play little role in maintaining a constant body temperature

What are two types of modified apocrine glands?

ceruminous and mammary glands

What are ceruminous glands?

found in the lining of the external ear canal, secretion mixes with sebum produced by nearby sebaceous glands to form cerumen (earwax), thought to deter insects and block entry of foreign material

What are mammary glands?

secrete milk

What are sebaceous glands (oil glands)?

simple branched alveolar glands that are found all over the body except in the thick skin of the palms and soles, secrete an oily substance called sebum, duct empties into a hair follicle or occasionally to a pore on skin surface

What is sebum?

central cells of the alveoli accumulate oily lipids until they become so engorged that they burst, called holocrine glands, the accumulated lipids and cell fragments constitute this

What does sebum do?

softens and lubricates the hair and skin, prevents hair from becoming brittle, and slows water loss from the skin, bactericidal (bacterium-killing)

The skin and its appendages perform a variety of functions, which includes….

• protection

• body temperature regulation

• cutaneous sensation

• metabolic functions

• blood reservoir

• excretion

Which is our most vulnerable organ system, exposed to microorganisms, abrasion, temperature extremes, harmful chemicals, and UV radiation?

the skin