SKIN

Integumentary system

Consists of the akin and accessory structures, such as hair, glands, and nails

Integument

Means covering

Epidermis

Embryonic ectoderm

Dermis and hypodermis

Mesoderm

Aquatic or terrestrial environment

The integument of vertebrates is a complex and large organ positioned at the interface with the __ and is derived from the embryonic ectoderm and mesoderm

Epidermis

Outer protective covering

Dermis

Connective tissue with blood vessels, nerves, and pigment cells

Hypodermis

Deeper fat and connective tissue

Anamiotes

Amphibians

Keratinization

Is the prevalent form of terminal keratinocytes differentiation

Intermediate filament keratins

The largest amount of proteins that are accumulated in these cells are __

Amniotes

Reptiles, birds, and mammals

Epidermis

In amniotes __, a variable process of soft or hard cornification takes place, which differs in intensity in different integument appendages, such as scales, feathers, hairs, claws, and horns

Epidermis

Is also one of the main immune organs as it contains numerous immune cells that build the initial anti-microbial barrier, and it is particularly active in terrestrial vertebrates

Dermis and hypodermis

In the __ of diverse vertebrates, a variable collection of fibroblasts, chromatophores, immune cells, lipoblasts, blood vessels, nerves, and other cell types are accumulated, allowing specific skin functions in the aquatic or land environment

Fish

Scales covered with mucus-secreting epithelium

Fish

Their mucus reduces friction, protects against pathogens, and aids osmoregulation

Amphibians

Moist, permeable skin with little keratization

Cutaneous respiration

Gas exchange of amphibians

Amphibians

Skin acts as a water absorption, defense via toxin

Reptiles

Keratinized epidermis with scales, prevents water loss

Reptiles

Provides mechanical protection, enables terrestrial survival

Birds

Feathers derived from keratinized epidermis, flight, insulation, waterproofing

Mammals

Hair and diverse glands, sebaceous, sweat, mammary

Mammals

Skin acts as thermoregulation, sensory input, communication, complex barrier defense

Protection, sensation, vitamin d production, temperature regulation, excretion

Integumentary system functions:

Protection

The skin provides this against abrasion, ultraviolet light, microorganisms, and water loss

Sensation

The integumentary system has __ receptors that can detect heat, cold, touch, pressure, and pain

Vitamin D production

When exposed to ultraviolet light, the skin produces a molecule that can be transformed into __

Temperature regulation

The amount of blood flow beneath the skin’s surface and the activity of sweat glands in the skin both help regulate body temperature

Excretion

Small amounts of waste products are lost through the skin and in gland secretions

Epidermis and dermis

The skin is made up of two major tissue layers:

Epidermis

Is the most superficial layer of skin

Epidermis, epithelial tissue

It is a layer of __ that rests on the dermis

Dermis

Is a layer of dense connective tissue

Skin, subcutaneous tissue

The __ rests on the __, which is a layer of connective tissue

Hypodermis

The subcutaneous tissue is not part of the skin

Epidermis

Prevents water loss and resists abrasion

Cutaneous membrane

Epidermis is also known as the __

Epidermis

Is a keratinized stratified squamous epithelium

Strata

The epidermis is composed of distinct layers called __

Stratum corneum

The most superficial stratum of the epidermis

Stratum corneum

Consists of dead squamous cells filled with keratin

Keratin

Gives the stratum corneum its structural strength

Mitosis

Cells of the deepest strata perform __

Stratum basale, 19

Single layer of cuboidal or columnar cells that undergo mitosis about every __ days

Stratum basale, one

__ daughter cells remains a __ cell and the other is pushed toward the surface

Stratum spinosum, lamellar bodies

Flattened cells that accumulate lipid-filled vesicles called __

Stratum granulosum

Flat, diamond-shaped cells that accumulate keratin and release the contents of the lamellar bodies

Stratum lucidum

Thin, clear zone, present only in certain areas

Stratum lucidum

Cells have no nuclei or organelles

Stratum corneum

Dead squamous dells filled with keratin, coated with lipids from the lamellar bodies

Stratum basale

Deepest layer of epidermis

Dermis

Is composed of dense collagenous connective tissue containing fibroblasts, adipocytes, and macrophages

Dermis

Nerves, hair follicles, smooth muscles, glands, and lymphatic vessels extend into the __

Collagen fibers and elastic fibers

__ of the reticular layer are responsible for the structural strength of the dermis and resistance to stretch

Papillary layer

Superficial layer just beneath the stratum basale of the epidermis

Papillary layer

Layer of the dermis made of loose connective tissue

Reticular lauer

Thickest layer of the dermis

Reticular layer

Composed of dense irregular connective tissue

Tension line

Cleavage line

Cleavage lines

In the skin are more resistant to stretch

Incision

An __ made parallel with these lines tends to gap less and produce less scar tissue

Stretch marks

If the skin is overstretched for any reason, the dermis can be damaged, leaving __

Substances

Are delivered at different depths, depending on how quickly the materials needs to be absorbed into the blood

Intradermal injection

Small needle at a shallow angle delivering into the dermis through a taunt skin for slow absorption

Subcutaneous injection

Skin pinched, small needle at a shallow angle

Intramuscular injection

Long needle at a 90-degree angle into a muscle, fast absorption

Melanin and carotene

The two primary pigments are __

Melanin

Is the group of pigments primarily responsible for skin, hair, and eye color

Brown to black, yellowish, reddish

Most melanin molecules are __ pigments, but some are __ or __

Melanin

Provides protection against ultraviolet light from the sun

Carotene

Is a yellow pigment found in plants such as squash and carrots

Melanin

Large amounts of __ from freckles or moles in some regions of the skin

Melanin

__ production is determined by genetic factors, exposure to light, and hormones

Genetic factors

Are responsible for the amounts of melanin produced in different races

Melanocytes

Since all races have about the same number of __, racial variation in skin color are determined by the amount, kind, and distribution of melanin

Exposure to ultraviolet light, suntan

In sunlight, stimulates melanocytes to increase melanin production, the result is a __

Albinism

Although many genes are responsible for skin color, a single mutation can prevent the production of melanin and cause __

Dermis

The color of blood in the __ contributes to skin color

Blood flow, pale

A decrease in __, as occurs in shock, can make the skin appear __

Blood O2, cyanosis

A decrease in the __ content produces a bluish color of the skin, called __

Bluish

A decrease in the blood O2, content produces a __ color of the skin, called cyanosis

Skin cancer

Most common cancer

UV light exposure

Skin cancer mainly caused by __

Skin cancer

Fair-skinned people are more prone to this

Skin cancer

Prevents by limiting sun exposure and using sunscreens

Tan

UVA rays cause __ and is associated with malignant melanomas

Malignant melanomas

UVA rays cause tan and is associated with __

UVA rays

__ cause tan and is associated with malignant melanomas

Sunburns

UVB rays cause __

UVB rays

This cause sunburns

Subcutaneous tissue

The skin rests on the __

Subcutaneous tissue, hypodermis

Not part of the skin, is sometimes called __

Hypodermis

Subcutaneous tissue

Subcutaneous tissue

Attaches the skin to underlying bone and muscle and supplies it with blood vessels and nerves

Subcutaneous tissue

It is loose connective tissue, including adipose tissue that contains about half the body’s stored lipids

Subcutaneous tissue

The amount and location of adipose tissue vary with age, sex, and diet

Adipose tissue

__ in the subcutaneous tissue functions as padding and insulation

Total body fat

Subcutaneous tissue can be used to estimate __