INTEG SYSTEM

Skin

Largest organ accounting for 16% of body weight and surface area of 2 meter square

Protective baddies

Prevents desiccation

Sensory organ

Maintenance of body temperature

Functions of the skin

Epidermis

Dermis

2 principal layers of the skin

Epidermis

surface epithelium

Dermis

Underlying connective tissue

Corium

Another term for dermis

Hypodermis

not part of the skin just beneath the dermis

made up of looser connective tissue that minimizes injury by permitting some degree of mobility

Keratinocytes

10-20 layers of cells that make up thick skin

Stratified squamous

Type of epithelial tissue in epidermis

Cytomorphosis

refers to cytological changes that the skin cells undergo in their upward movement

20-30 days

Transit time of cytomorphosis

Stratum basale

Stratum spinosum

Stratum granulosum

Stratum corneum

Four zones of epidermis

Stratum basale

Simple cuboidal with nuclear that are large that lies on basal lamina

Cells in mitosis are common

Stratum spinosum

Flatter polyhedral shape

Contains lamellar bodies which are secretory granules

Lamellar bodies

are secretory granules

Stratum granulosum

Consists of 3-5 layers that are more flat than the stratum spinosum

Keratohyalin granules

Contained in stratum granulosum

Stratum corneum

Consists of 3-5 rows of very flat dead cells

Contains no nucleus or organelles

Desmosomes

are no longer present in stratum corneum

Stratum lucidum

Thick epidermis

Between the stratum granulosum and corneum

Thin clear zone made of 1 or 2 rows of flat translucent keratinocytes

Not found in thin epidermis

Carotene

Gives inherent yellowish color

Hemoglobin

Pink tint

Melanin

Gives Brian’s to black color produced by specialized cells; found at basal layer of epidermis and occasional in the dermis

Melanocytes

Specialized cells of melanin

Langerhan cells

Solitary cell type found widely distributed in the epidermis

Upper layer

Langerhan cells usually lived in what layer of stratum spinosum

Langerhan cells

Participated in body’s immune response

Merkel cells

Found in basal layer of the epidermis over the entire body

Finger tips

Merkel cells abundant here because of their important role in sensory perception

Dermis

Tough layer of connective tissue immediately beneath the epidermis makes up the greater part of the thickness of the skin

0.6mm

Dermis Size in eyelids

3mm

range at palms and soles

Papillary layer

Reticular layer

Two layers of the dermis

Papillary layer

Fibroblast are widely distributed in the bundles of type III collagen and loose network of elastic fibers

Capillaries

is contained in papillary layer

Reticular layer

much thicker layer made up of closely packed, coarser bundles of type II collagen fibers

Fibroblast

Macrophages

Lymphocytes

Mast cells

found in the reticular layer

Skin Appendages

This extends to dermis and sometimes into subcutaneous tissue

Hair follicles

Hair develops in deep invaginations of the epidermis

Hair

Absent only in palms, soles, lateral aspect of the feet, glands; penis, clitoris and labia minora

Arrector pili muscle

Muscle fibers that run diagonally upwards from the follicle to the papillary layer of the dermis

Responsible for goose flash when we are cold

new hair shaft forms

After resting phase the old hair is shed and ___

Nails

Plates of closely compacted hard keratin

Proliferation

Keratinization

forms the nail matrix

Proximal nail folds

Nail root and matrix are located under a fold of skin called

Eponychium

Epidermis that extends onto the upper sauce of the nail about 0.3 to 1mm

Lunula

Anterior portion of nail matrix that is opaque white crescent as seen thru the nails

Sebaceous gland

Appendices of hair follicle found through out the dermis except where hair is lacking

Sebum

Maintained soft tribute of thin skin and flexibility of hair

Triglycerides, cholesterol and waxes

secretion rich in sebum

Holocrine

Type of gland that looses whole cells and its content

Apocrine sweat glands

Second kind of sweat gland that are found at axilla mons pubis and in the circumanal region

Canal of hair follicle

Where apocrine ducts open

merocrine gland

Type of gland according to secretion

There is fusion of membrane of secretory granules with the cells membranes of the gland

Growth phase

Regressing phase

Resting phase

3 phases of hair growth

2-6 years

Growth phase last for

2-3 weeks

Regressing phase last for

3-4 months

Resting phase last for

Rete cutaneum

Found at the boundary between the hypodermis and dermis

Rete subpapillare

Located in papillary layer of dermis

Eccrine sweat glands

Tubular glands widely distributed through the skin with their secretory portion deep in the dermis or in the hypodermis

Sweat pore

Where the gland opens on the __ on the surface of the skin

Serous type

what type of secretion is eccrine sweat glands

Free nerve endings

efferent nerves that activate the glands if the skin and control blood flow

sensing pain and temperature

Afferent function of nerves

Pacinian corpuscles

in the dermis and hypodermis are ovoid structures up to 1 mm in length

Resembles onion in cross section

Meissner’s corpuscles

Pear shaped structure made up of flattened cells oriented transversely resulting in ladder like appearance in section

Occasionally found in dermal papillae

Mechanoreceptors

sending light deformation of skin

Krau’s ends -bulbs

are small spheroudal cried in papillary layers of the dermis bear little resemblance to pacinian corpuscles but much smaller and lack concentric lanellae