NVCC BIO 141 Chapter 5

Define Hypertrophy

increase in cell size

Define Hyperplasia

increase in number of cells

Define Atrophy

decrease in cell size

Define Dysplasia

abnormal development

Define Neoplasia

the formation or presence of a new, abnormal growth of tissue (tumor)

List the two main layers of skin and name the layer below it

Epidermis

Dermis

Hypodermis

Describe the structure and function of the hypodermis

binds skin to underlying tissue & more adipose than dermis

function: energy reservoir, thermal insulation

List and briefly explain the five main functions of the skin

Protection: protect underlying tissues from damage/pathogens

Sensation: sensory receptors allow for sensation

Thermoregulation: maintenance of stable internal body temp.

Excretion: lactic acid/urea + small amount of toxins/metals through sweat

Vitamin D Synthesis: precursor to Vitamin D is in deep epidermis that reacts with UV rays to make Vitamin D

Describe the Stratum Basale layer

deepest layer

single layer with cuboidal cells that attach to the basement membrane

closest to blood supply so metabolically/mitotically active

Describe the Stratum Spinosum layer

2nd deepest

thickest stratum; spiky; close to blood supply so metabolically/mitotically active

Describe the Stratum Granulosum layer

middle layer

has keratin bundles/lipid-base substances acting as water barrier and maintaining moisture in the skin

Describe the Stratum Lucidum layer

narrow clear layer of dead keratinocytes found only in thick skin of hands and feet

Describe the Stratum Corneum layer

most superficial layer

several layers of dead flattened keratinocytes and can shed off

Describe characteristics and lifecycle of keratinocytes

Corneum layer continually sheds dead keratinocytes which get replaced by mitosis of basale/spinosum layers that push cells above them to superficial layers; as cells go away from bloody supply they died and cycle continues

What is the function of Keratinocytes?

produce keratin which makes cells rough and waterproof

What is the function of Melanocytes?

produce the pigment melanin in basal layer

What is the function of Merkel cells?

touch receptors that sense light touch and different shapes/textures

found in: fingertips, lips, base of hairs

What is the function of Langerhans cells?

To help protect the body from infection

Describe Thick Skin

found in hands and soles of feet that lack hair follicles but have sweat glands

has Lucidum layer and thicker Corneum layer

Describe Thin Skin

has hairs and sebaceous/sweat glands, more flexible, covers rest of body

No Lucidum layer with thinner corneum layer

Describe the Papillary layer of Dermis

superficial layer of loose connective tissue with special collagen fibers that extend up to anchor the epidermis

Contains Meissner Corpuscles: respond to light pressure/vibrations

Describe the Reticular layer of Dermis

deeper/thicker layer made of dense irregular connective tissue that strengthen the dermis and help prevent traumatic injuries from reaching deep into skin

allows elasticity

Contains Pacinian Corpuscle: responds to deep pressure/vibrations

Explain the advantage of having friction ridges

enhances gripping in hands and feet

Explain how friction ridges are used in the identification of individuals

It is unique for each individual and sweat glands along the ridges leave a film called a fingerprint that can be used for identification

Describe the composition of cleavage lines

gaps between bundles of collagen that indent the epidermis

runs in circular patters in neck and trunk but longitudinal in head and limbs

Explain the importance of cleavage lines

if the skin is cut parallel to lines then edges stay closed and heal better with less risk of scarring

Explain the formation of stretch marks

when skin is extremely stretched during rapid weight game or pregnancy that causes tears in skin that are permanent

Describe Melanin

primary skin pigment ranging from orange-red to black found in basal layer

protects DNA from UV rays but only can absorb some of the UV rather than all

Describe Carotene

Yellow to orange, most obvious in the palms and soles

comes from diet

Describe Hemoglobin

Iron containing protein in red blood cells that gives a pink hue

Define erythema

superficial reddening of the skin, usually in patches, as a result of injury or irritation causing dilatation of the blood capillaries.

Explain thermoregulation of the skin

dilated blood vessels allow for heat loss which is why for fair skin people you can see them get red when they are hot

Describe the structure of Hair

Hair consists of a hair shaft produced by the follicle embedded in the skin, the shaft consists of the outer cuticle, the cortex, and the medulla.

Describe the functions of hair

assist in thermoregulation but body hair too sparse to play significant role

helps protect and feel sensation

Name the three different types of hair

Lanugo: thin nonpigmented hair over entire body as fetus

Terminal: thicker, courser, pigmented on scalp and around eyes

Vellus: thinner, nonpigmented hair over body and during puberty most of it is replaced by terminal

Describe the structure of Nails

A nail is a scale-like modification of the epidermis that forms a clear, protective covering

Nails are made up of hard keratin and have a free edge, a body, and a proximal root

Explain nails growth

grows 0.5mm a week (toes grow slower)

Describe Eccrine (Merocrine) Sweat glands

sweat exits the duct and secretes through sweat pores

99% water with electrolytes and waste products like lactic acid

Primarily for thermoregulation but also protection from pathogens

Describe Apocrine Sweat glands

found in armpits, anal, areolae areas

releases thick sweat rich in proteins into hair follicles

influenced by sex hormones (not active until puberty)

Describe Sebaceous Glands

forms along the sides of the walls of the hair follicle and produces sebum (waxy/oil mix)

uses holocrine secretion

retains moisture and kills/deters bacteria

Describe a 1st Degree burn

red

no blister

resolves in 7 days

does not require medical attention

Describe a 2nd Degree burn

Erythema

Pain

Superficial blisters

required medical attention

Describe a 3rd Degree burn

possibly reaches muscles/bone

not painful since nerves are too damaged

increase risk of dehydration and infection

may require skin grafting

Describe the Rule of Nines

Divides the body into 11 areas, each accounting for 9% of total body area, plus an additional area surrounding the genitals accounting for 1% of body surface area.

Head (4.5%)

Trunk (18%)

Single Arm (4.5%)

Single Leg (9%)

Genitals (1%)

Describe Basal Cell Caranoma Cancer

most common cancer

keratinocytes in basal layer forming crater on skin regularly exposed to UV

destructive to local tissue but doesn't generally metastasize to other tissue

surgical removal generally fixes issue

Describe Squamous Cell Carcinoma Cancer

2nd most common skin cancer

cancer of keratinocytes of spinosum

form scaly plaques that bleed/ulcerate

most common on head/neck

more likely to metastasize but typically can be managed with surgery

Describe Malignant Melanoma Cancer

most dangerous skin cancer

cancer of melanocytes

can be distinguished from normal moles using ABCDE rule

early detection is critical ins it has increased risk of metastasizing since it extends to dermal blood vessel and spreads through blood stream

Describe the ABCDE rule

Asymmetrical Shape

Border Irregularity

Color (blue-black)

Diameter usually larger than 6mm

Evolving shape and size