BIO135 ch5,6,8

Skin Functions

barrier for protection, body temperature regulation, cutaneous sensations, metabolic functions (creates precursor to vitamin D, which body needs to absorb calcium), blood reservoir (veins), and excretion of wastes

Layers of Skin

Epidermis (top), Dermis (middle), and Hypodermis (bottom)

Epidermis

Thin (4 layers) or Thick Skin (5 layers), 4 cell types

Keratinocyte

Main cell of Epidermis, produces keratin and held together by Desmosomes. Made in Basale layer and moves up through layers of Epidermis

Desmosomes

Interlocking junctions between cells to keep cells attached

Melanocyte

Spider shaped cell producing Melanin and found in Basale layer. Transforms melanin into membrane bound granules called Melanosomes

Dendritic (Langerhaans)

Star shaped cells that arise from bone marrow, key activators of the immune system

Tactile (Merkel)

Sensory receptors that sense touch

Thick Skin Epidermis

Covers: Palms, Fingertips, and Soles of feet. 5 Layers (superficial to deep): corneum, lucidum, granulosum, spinosum, and basale

Thin Skin Epidermis

Covers: Most of body. 4 layers (superficial to deep): corneum, granulosum, spinosum, and basale (NO LUCIDUM)

Corneum

Many rows of dead cells that slough off. Keratin and proteins protect skin while glycolipid makes it nearly waterproof

Lucidum

Few rows of flat dead keratinocytes (THICK SKIN ONLY)

Granulosum

Keratinization (cells fill with keratin) begins. 2 types of granules: Keratohyaline (helps to form keratin) & Lamellar (contain glycolipid to slow water loss)

Spinosum

Several layers thick, containing filaments made of pre-keratin. Dendritic cells most common

Basale

Deepest layer of epidermis where new cells are created

Epidermis Layers

Dermis

Fibroblasts and macrophages found here. Makes up "hide" used to make leather. Contains nerves, blood vessels, lymphatic vessels, hair follicles, oil glands, and sweat glands. 2 Layers: Papillary (top) & Reticular (bottom)

Papillary Dermis

Superficial layer made of areolar tissue. In thick skin: creates "friction ridges" (fingerprints)

Reticular Dermis

Dense irregular tissue makes up this deep layer. Contains many elastic and collagen fibers that bind water to stay hydrated. Contains: extracellular matrix containing pockets of adipose cells & Cutaneous Plexus (network of blood vessels between reticular, hypodermis, and cleavage lines)

Cleavage Lines

Collagen and elastic fibers in the dermis, arranged in parallel bundles (surgeons use this to create better healing incisions)

Flexure Lines

Dermal folds at or near joints. Caused by: Dermis being tightly secured to deeper structures causing skins inability to slide easily creating deep creases. Visible on hands, wrists, fingers, soles, and toes.

Striae (Stretch Marks)

Extreme stretching of skin causes dermal tears

Blisters

Acute short term trauma to skin, fluid filled pockets separating Epidermal and Dermal layers

Melanin, Carotene, and Hemoglobin

3 pigments that contribute to skin color

Melanin

Main pigment, made by melanocytes, and shields DNA of keratinocytes from UV light. 2 forms: reddish yellow and brownish black

Carotene

Yellow orange pigment, seen in palms and soles. Accumulates in corneum and hypodermis. able to be converted into vitamin A for vision and epidermal health

Hemoglobin

Pinkish hue in fair skin caused by lower levels of melanin. Reflects crimson color in the red blood cells circulating through the dermal capillaries

Cyanosis

Blue skin, low oxygen

Pallor

Pale / lack of color, anemia

Erythema

Redness, fever

Jaundice

Yellow, liver disorder

Hair

Consists of dead keratinized cells

Regions of Hair Shaft

Medulla- center, contains soft keratin not found in fine hairs. Cortex- several layers of flat cells that surround the medulla. Cuticle- Outermost layer and heavily keratinized.

Shaft / Root of Hair

Above scalp (keratinization complete) / Within scalp (keratinization still ongoing)

Hair Bulb

Expanded area at deep end of follicle

Hair Follicle Receptor (root hair plexus)

Sensory nerve endings that wrap around hair bulb

Hair Papilla

Dermal papilla protrudes into hair bulb, containing knot of capillaries signaling hair to grow. If destroyed, follicle completely stops producing

Wall of Hair Follicle

Fibrous sheath (external), Glassy membrane (basement membrane of follicle epithelium), Epithelial root sheath (external & internal. external: continuation of epidermis. internal: derived from matrix cells), Hair matrix (makes new hair cells), and Arrector Pili (smooth muscle attached to follicle, acting as lubricant, also causes goosebumps)

Vellus Hair

Pale and fine body hair of children and adult females

Terminal Hair

Coarse, longer, and darker hairs of eyebrows, eyelashes, and scalp. Starting at puberty, also grow in armpit and genital regions of men and women. Also found in men on face, chest, arms, and legs

Nail Regions

Free Edge- tip. Nail Plate- superficial portion of nail bed. Root- superior to cuticle and inferior to proximal nail fold. Nail Bed- Bed of epidermis underneath keratinized nail plate. Nail Matrix- thick part of nail bed (causes nail growth). Lunule- overlies thick nail matrix appearing as white crescent. Nail Folds- borders of nail overlapped by skin folds. Cuticle- Eponychium. Hyponychium- Thick region beneath free edge where dirt accumulates, secures free edge

Sudoiferous Glands

Sweat glands, 2 types: Eccrine (merocrine) and Apocrine

Eccrine (merocrine) Glands

Most common, coiled into dermis and duct extends to open in a funnel shaped pore at skin surface

Apocrine Glands

Sweat glands found in armpits and genital regions. Lies deep in dermis and secretes into hair follicles. Secretion is odorless and thick with milky or yellowish color. When bacteria breaks it down, it leads to an odor known as body odor. 2 modified types: Ceruminous and Mammary

Ceruminous Glands

Lining of out ear canal, secretes ear wax

Mammary Glands

Secretes milk

Sebaceous Glands

Oil glands, found everywhere except for thick skin

Seborrhea

Cradle cap in infants caused by overactive sebaceous glands

3 Major Skin Cancers

Basal cell carcinoma, Squamous cell carcinoma, and Melanoma

Basal Cell Carcinoma

Most common and least severe (and metastic) type of skin cancer; often characterized by light or pearly nodules, and found in basale layer of epidermis

Squamous Cell Carcinoma

Skin cancer that metastasizes easier than basal cell, making it more dangerous; often characterized by scaly red papules or nodules, and found in keratinocytes of spinosum

Melanoma

Most dangerous form of skin cancer as it is highly metastatic and resistant to treatment; often characterized as a spreading brown to black colored patch, and can begin anywhere there is pigment

ABCD Rule

The American Cancer Society's rule for determining the presence of melanoma. A- Asymmetry, 2 sides of mole do not match. B- Border Irregularity, exhibits indentations. C- Color, contains several colors (black, brown, tan, sometimes red or blue). D- Diameter, larger than 6mm (pencil eraser). Occasionally used: E- Evolving, changes with time

Dehydration and Electrolyte Imbalance

Immediate threat of burns as it can cause renal failure and circulatory shock

Rule of Nines

Evaluation of fluid loss caused by burns by breaking body into 11 sections with each section

1st Degree Burn

Epidermis damage only, known as partial thickness burn ex: sunburn. Symptoms: Localized redness, edema (swelling), and pain. Heals in 2-3 days

2nd Degree Burn

Epidermal and upper Dermal damage only, known as partial thickness burn. Symptoms: Localized redness, edema (swelling), pain, AND BLISTERS. Heals in 3-4 weeks.

3rd Degree Burn

Entire thickness of skin damaged, known as full thickness burn. Symptoms: Skin color appears gray-white, cherry red, or blackened. No edema (swelling) seen, no pain felt (nerve endings destroyed). Skin graft usually required.

Critical Burns

25% of body with 2nd degree burns. > 10% of body with 3rd degree burns. Face, hands, or feet bear 3rd degree burns

Long Bones

Longer than they are wide, all limb bones EXCEPT patella. Contain diaphysis, epiphyses, membranes, and blood vessels and nerves

Short Bones

Cube shaped bones of the wrist and ankle. Contain thin plates of spongy bone covered by compact bone, bone marrow throughout. Plates sandwiched between connective tissue membranes. No: cylinder shape, shaft, expanded ends, and marrow cavity

Flat Bones

These bones are thin, flat, and curved. They form the ribs, breastbone, and skull. Contain thin plates of spongy bone covered by compact bone, bone marrow throughout. Plates sandwiched between connective tissue membranes. No: cylinder shape, shaft, expanded ends, and marrow cavity

Irregular Bones

Bones of vertebrae, face and pelvis. Contain thin plates of spongy bone covered by compact bone, bone marrow throughout. Plates sandwiched between connective tissue membranes. No: cylinder shape, shaft, expanded ends, and marrow cavity

Compact Bone

Dense, hard layers of bone tissue that lie underneath the periosteum

Spongy Bone

Layer of bone tissue found just inside the layer of compact bone, contains trabeculae

Diaphysis

Forms shaft of bone, constructed of thick compact bone that surrounds a central medullary cavity or marrow cavity that contains no bone tissue, only marrow. In adults, medullary cavity holds yellow marrow (fat)

Epiphysis

Bone ends, outer compact bone shell forms epiphysis exterior and interior contains spongy bone

Epiphysis Plate / Line

Plate of hyaline cartilage at junction of diaphysis and epiphysis, providing growth of length in long bone / Remnant of epiphyseal plate

Peristoeum

Double layer connective tissue that covers external surface of entire bone except joint surfaces. Rich with nerve fibers and blood vessels, serving as anchoring points for tendons and ligaments

Osteogenic Layer

Next to bone, contains osteogenic cells (primitive stem cells)

Endosteum

Inner layer of connective tissue, covers internal bone surfaces. Specifically, covers trabeculae of spongy bone, lines canals that pass through compact bone, and contains osteogenic cells

Sharpay's Fibers

Connect periosteum to bone

Red Marrow in Bone

Found within trabecular cavities of spongy bone, diploe of flat bones, medullary cavities, and spongy bone of newborns. Adult bones have little red, but yellow marrow can convert to red if needed

Osteogenic Cells

Found in Periosteum and Endosteum and develop into osteoblasts

Osteoblast Cells

Actively mitotic bone forming cells, BUILDS NEW BONE

Osteocyte Cells

Mature bone cells in lacunae, monitors and maintains bone matrix

Bone Lining Cells

Flat cells found on bone surfaces where no bone remodeling is ongoing

Osteoclast Cells

Breaks down bone tissue during bone remodeling, CRUSHES BONE

Osteon / Haversian System

A unit of bone containing central canal and matrix rings

Lamellae

Rings around the central canal, sites of lacunae

Central (haversian) Canal

Opening in center of an osteon, carries blood vessels and nerves

Caniculi

Passageways connecting lacunae to each other and to other central canal

Ossification / Osteogensis

Process of bone formation

Intramembranous Ossification

Bone forms directly from mesenchymal tissue

Endochondral Ossification

Bone forms by replacing hyaline cartilage

Appositional Growth

Growth in width/thickness

Interstitial Growth

Growth in length, 5 stages within 5 zones of cartilage

1. Resting Zone

Inactive cartilage on epiphyseal side of epiphyseal plate

2. Proliferation Zone

Cells divide quickly, pushing epiphysis away from diaphysis which lengthens bone

3. Hypertrophic Zone

Older chondrocytes hypertrophy (enlarge), the lacunae erode and enlarge, leaving interconnecting spaces

4. Calcification Zone

Surrounding matrix calcifies, chondrocytes die, and deteriorate

5. Ossification Zone

Osteoclasts erode cartilage spicules, osteoblasts cover them with new bone, and eventually being replaced with spongy bone

Parathyroid Hormone

Regulates calcium in blood and bone, calcitonin may be involved. When blood calcium falls, PTH releases osteoclasts. Less fat makes it harder to build new bones. High serotonin levels slow down bone creation

Wolff's Law

Bones reflect the stresses they encounter. More stress / more work on bones = thicker bones

Non-Displaced Fracture

Bone ends retain their normal position

Displaced Fracture

Bone ends out of normal position

Complete Break

Bone broken all the way through

Incomplete Break

Bone not broken all the way through

Open (compound) Fracture

Broken bone penetrates through skin

Closed (simple) Fracture

Broken bone does not penetrate skin