Bio 141, Chapter 5, Integumentary System – Flashcards

• Top layer of our skin • Thick skin has all five layers: palms, fingertips, soles. • Thin skin just lacks the stratum lucidum layer, the other 4 layers are thinner • five layers • Four cells • keratinized (=dead cells) stratified squamous epithelium

It has four: Kerotinocytes, Melanocytes, Dendritic, Tactile

• Most epithermal cell, produce keratin gives the epidermis its tough protective structure • Arise from the deepest layer (stratum basale) • Undergo continuous mitosis • New epidermis every 25-45 days • Callus= thickened epidermis as a result of persistent friction

• Synthesize the pigment melanin • Found in the stratum basale • Melanin granules (=melanosomes) transferred to keratinocytes where they accumulate on superficial side of nucleus.

Formed a protective shield that protects the nucleus from the sun's UV radiation.

• Ingest foreign substances • Key activators of the immune system • Arise from bone marrow, migrate to the epidermis

• Present at the epidermal-dermal junction • Associated with a disclike sensory nerve ending to form tactile or Merkel disc.

This disk works as a sensory receptor for touch

from deepest to most superficial: stratum basale, stratum spinosum, stratum granulosum, stratum lucidum, stratum corneum

• Deepest layer • Mostly a single layer of stem cells • Continuous renewing cell population—youngest keratinocytes • Stratum germinativum rapid division of cells, on going mitosis. • 10-25% of cells here are melanocytes • tactile cells are also present

• Several layers thick • Pre-keratin filaments attached to desmosomes (connecting junctions) • Abundant melanin granules and dendritic cells scattered among keratinocytes

• 4-6 layers • Where keratinization (cells fill with keratin) begins • Two types of granules: o Keratohyalinehelps form keratin o Lamellar forms water barrier with a glycolipid slows down water loss, makes the cells more resistant to destruction, making the outer layers the strongest ones.

• 2-3 layers of clear, flat, dead keratinocytes • only in thick skin • Because this layer and the stratum corneum are too far from the capillaries (dermis), they are not receiving nutrients, so they die.

• Outermost layer • 20-30 cells layer thick • ¾ of epidermal thickness • anucleate • dead cells (apoptosis normal sequence of cells dying. Organelles break down, plasma membrane thickens protecting us from abrasion and penetration, our outer layers are able to protect the inner ones from the harsh environment • Average person sheds 50,000 dead cells every minutes = 18kg/40lbs over a lifetime

• Consists of papillary and reticular layers • Strong dense connective tissue with rich supply of nerve fibers, blood vessels and lymphatic vessels • Contains hair follicles, oil glands, and sweat glands • Only the dermis is vascularized, therefore it is better nourished

fibroblasts, macrophages, some mast cells, and white blood cells

. Thin, superficial layer of areolar connective tissue . Dermal papillae project into epidermis . In thick skin it lies on dermal ridges and form epidermal ridges . Friction ridges= dermal ridges + epidermal ridges . Genetically determined and unique to each person . Sweat pores open along the ridges and create fingerprints on things we touch . Lamellar corpuscles= receptors

. Deeper layer of dense fibrous connective tissue ~80% of dermal thickness . Cutaneous plexus lies between this layer and hypodermis . Cleavage (tension) lines: separations or less dense regions between collagen fiber bungles . Flexure lines= dermal folds at or near joins where dermis is tightly secured to deeper structures . Striae= Silvery white scars due to tears in dermis (stretch marks) . Blisters= fluid-filled pocket that separates epidermal and dermal layers

Subcutaneous tissue just deep to skin; also called superficial fascia; consists mostly of adipose tissue

Melanin, carotene, and hemoglobin

. Made in the skin by melanocytes (found in deepest layer) . Polymer of tyrosine amino acids; reddish yellow to brownish black in color . All humans have same relative number of melanocytes but vary in kind and amount made . Freckles and pigmented nevi (=moles) are local accumulations of melanin

. Yellow-orange pigment in certain plants . Accumulates in stratum corneum and fatty tissue of hypodermis . Converted into vitamin A good for our eyes

Crimson pigment that carries oxygen in red blood cells.

A bluish discoloration of the skin resulting from poor circulation or inadequate oxygenation of the blood.

Redness, blushing, fever, hypertension, inflammation or allergy

May signify anemia or low blood pressure. Types of emotional distress (anger, fear)

Yellow skin tone= liver disorder

Bronze, almost metallic appearance of the skin, a sign of Addison's disease adrenal cortex produces inadequate amounts of its steroid hormone, or sign of pituitary gland tumors that inappropriately secrete melanocytes stimulating hormone

Blood escaped from the circulation and clotted beneath the skin (blood swelling)

Sense insects Guard against physical trauma/heat loss/sunlight Shield eyes Filter particles in nose Hair acts as sensitive touch receptors

Shaft, root, follicle, bulb, papilla, matrix

Shaft: portion where keratinization is complete Root: Keratinization is still going on

Hair pigmentation is made by melanocytes at base of follicle

1. Medulla: only part with soft keratins, no fine hairs, central core 2. Cortex: surrounds the medulla, consists of several layers of flattered cells 3. Cuticle: single layer of cells overlapping each other. Provides strength and helps keep inner layers compacted

1. Hair bulb 2. Hair papilla 3. Hair matrix 4. Arrector pili

Wall of hair follicle is composed of peripheral connective (fibrous) tissue sheath, thickened basal lamina (glassy membrane), and epithelial root sheath.

Surrounded by hair follicle receptor (root hair plexus)

Protrudes into bulb and provides nutrients

Actively dividing area of hair bulb that produces the hair

Smooth muscle cells associated with each hair follicle

• Vellus hair: pale and fine, found in children and adult females • Terminal hair: coarser, longer hair of eyebrows and scalp • Hirsutism: excessive hairiness

• Rate of hair growth varies with body region, sex, and age. Averages 2.5mm per week • Follicles go through growth cycles, active growth phase followed by regressive phase • On average, 90 scalp hairs are lost daily

Baldness, hairs being shafted faster than they are replaced

Most common type, genetically determined, sex-influenced.

Nails are like scale modifications of the epidermis that forms a clear protective cover

Free edge, nail plate (body), root

Deeper layers of epidermis beneath nail

Thickened proximal portion of nail bed, responsible for nail growth

Thickened region beneath free edge; informally known as the "quick"

Skin folds along projects onto nail body as cuticle (eponychium)

Nails look pink from dermal capillaries, region over nail matrix appears as a white crescent (lunule)

Distributed over entire skin surface except nipples & parts of external genitalia; up to 3 million per person

Eccrine and apocrine

. Most numerous sweat gland; abundant on palms, soles, & forehead; prevents overheating • duct opens into pore on skin surface; release of sweat is via exocytosis • sweat = 99% water with some salts (mostly NaCl), vitamin C, antibodies, microbe-killing peptide (dermcidin), & traces of metabolic waste (urea, uric acid, & ammonia); pH between 4 & 6

. Mostly confined to axillary & anogenital areas; about 2000 are present; begin functioning at puberty • actually merocrine glands that release their product via exocytosis • larger than eccrine glands, lie deeper in dermis, & ducts empty into hair follicles • product contains same basic components as true sweat, plus fatty substances & proteins; thus it is viscous & sometimes has a milky or yellowish color; odorless until bacteria decompose it • ceruminous glands = modified apocrine glands in lining of external ear canal; help form cerumen (ear wax) • mammary glands = specialized sweat glands that secrete milk

1. Eccrine sweat glands are never connected to hair follicles, whereas apocrine sweat glands are. 2. Eccrine sweat glands produce a watery secretion, whereas apocrine secretion is more viscid.

- found all over body except in thick skin of palms & soles - holocrine glands that secrete sebum - lubricate the skin and hair. - most develop as outgrowths of hair follicles & secrete sebum into follicle - whitehead vs. blackhead - acne = active inflammation of sebaceous glands accompanied by "pimples" (pustules or cysts); usually due to bacterial infection -seborrhea = overactive sebaceous glands

Consists of the skin, hair, nails, glands, and nerves. Its main function is to act as a barrier to protect the body from the outside world. It also functions to retain body fluids, protect against disease, eliminate waste products, and regulate body temperature.

Chemical, physical, and biological barriers.

. skin secretions: acid mantle (low pH), dermcidin in sweat, bactericidal sebum, defensins, cathelicidins • melanin prevents UV damage to skin cells

• continuity of skin & hardness of keratinized cells • protective due to structure of stratum corneum (many layers of dead flat cells with surrounding glycolipids) • ward off bacteria & block most diffusion of water • substances that penetrate skin: lipid-soluble substances, oleoresins, organic solvents, salts of heavy metals, selected drugs, penetration enhancers

• dendritic cells: present antigens to immune system • dermal macrophages: dispose of viruses & bacteria that manage to penetrate epidermis • DNA: converts UV radiation to heat

- insensible perspiration—routine & unnoticeable sweating • 500mL sweat/day under normal rest conditions with environmental temperature below 31-32°C (88-90°F) - sensible perspiration—visible output of sweat • up to 12L of body water loss on a hot day

- skin richly supplied with cutaneous sensory receptors; classified as exteroceptors • tactile (Meissner's) corpuscles, tactile discs, lamellar (Pacinian) corpuscles, hair follicle receptors, free nerve endings

- form vitamin D precursor in sunlight - keratinocyte enzymes make chemical conversions that supplement those of the liver • disarm cancer-causing chemicals, convert harmless chemicals into carcinogens, activate steroid hormones - make biologically important proteins (such as collagenase)

- dermal vascular supply can hold about 5% of body's entire blood volume

- eliminates limited amounts of nitrogen-containing wastes (ammonia, urea, uric acid) in sweat - water & salt loss during profuse sweating

Gives the body its overall shape, loss of this function can be seen with the drooping of skin with age.

Bacterial infection is not. While it is true that infection is a long term threat, the fluid balance must be restored first in order to stabilize the burn trauma. Renal failure can occur as a result of dehydration and electrolyte imbalances causes by a burn.

Sweat is used for thermoregulation. As sweat is released onto the surface of the epidermis, heat from the body is conducted into the water. Water is a better conductor of heat than air is. As the sweat evaporates, the heat from the body dissipates into the environment.

Melanin is the only one of the three pigments (melanin, carotene, and hemoglobin) that contribute to skin color that is actually produced in the skin itself.

Root hair plexus: allows the hair to assist in touch sensation

Stratum Basale

Sebaceous glands secrete an oily substance called sebum. Sebum softens and lubricates the hair and skin, slows water loss from the skin when external humidity is low, and has bactericidal properties.

Between 10 and 25% of the cells in the stratum basale are melanocytes that produce the melanin.

The loose connective tissue within the papillary layer of the dermis is rich in blood vessels and cells that function in the body's defenses.

The hypodermis anchors skin to the body.

Sebaceous glands occur over the entire body, with the exception of the palms and soles of the feet.

Sebaceous glands are simple branched alveolar glands with several alveoli opening into a single duct.

Dense irregular connective tissue

The superficial layer of the skin, the epidermis, is composed of thick keratinized stratified squamous epithelium.

Apocrine glands start to function at puberty under the influence of androgens. Their activity is increased by sexual foreplay, and they enlarge and recede with the phases of a woman's menstrual cycle.

Sweat pores open along the crests of the epidermal ridges, leaving distinct fingerprints on touched surfaces.

Stratum basale