Chapter 1: Skin & Hair Anatomy

What is the pilosebaceous unit?

The hair follicle and its appendages.

Where does skin color derive from?

1. Melanin produced in the stratum germinativum.

2. Carotene, a yellowish pigment

3. Concentration of blood vessels found in the dermis.

Where is skin the thickest and thinnest? And approximately how thick and thin?

1. Thickest in the soles of the feet; 1/5th of an inch

2. Thinnest in the eyelids; 1/12th of an inch

The skin is the body’s largest organ covering up to ? on the average person.

20 square feet

Skin is made up of which two types of tissue?

1. Epithelial Tissue (“No Blood”/Epidermis)

2. Connective Tissue

What are the three main layers of the skin?

1. Epidermis

2. Dermis

3. Subcutaneous

What are the other names for Epidermis?

1. Scarf

2. Cuticle

3. No Blood

4. Epithelial

What are the other names for the dermis (has blood)?

1. Living Tissue

2. Living Layer

3. Corium

4. Connective Tissue

5. Cutis Vera

6. Derma

7. True Skin

What are the other names for subcutaneous?

1. Hypodermis

2. Subcutis

3. Adipose Tissue/Fat

The epidermis consists of layers made of ? .

Stratified epithelium (no blood)

The process of living cells moving upwards and changing to dead cells is known as ? .

Keratinization

The 2 main zones of the epidermis are:

1. The Horny Zone

2. The Germinal Zone (Living/Basal Zone)

The Horny Zone consists of which layers?

1. Stratum Corneum

2. Stratum Lucidum

3. Stratum Granulosum

The Germinal Zone consists of which layers?

1. Stratum Spinosum

2. Stratum Germinativum

Tell me about the Stratum Corneum:

Also known as the outermost layer of the skin or “superficial layer”, this is where dead skin cells are constantly shed, even through the friction of changing clothes. These cells are predominantly bound by sebum (the skins natural lubricant).

Tell me about the Stratum Lucidum:

Only found in the palms and soles of the feet where the epidermis is thickest, not found in thin skin. Gets its name from the transparent nature of the cells that contain eleidin (a clear protein), a clear substance derived from keratohyalin granules.

Tell me about the Stratum Granulosum:

Grand Slam = Baseball Players = Have Calluses

Persistent friction and pressure cause areas to thicken for protection and form calluses. It is thickest on soles of feet, followed by palms. Also known as the granular layer. The lower cells have nuclei and are still living. As these cells are pushed upwards by new cells, they lose their nuclei and die. This layer gives skin its opaque appearance due to presence of keratohyalin granules in the cytoplasm.

Tell me about the Stratum Spinosum:

Also known as the prickle cell layer because of the cells’ prickley (spiney) shape.

Tell me about the Stratum Germinativum:

Also known as the Basal Layer, Innermost Layer or Lowest Layer of the Epidermis.

Cell division (mitosis) occurs here, new epidermal tissue is formed and begins migrating to the surface of the skin, replacing dead skin cells that have been shed. This process is known as desquamation and takes approx. 28 days (much less is babies/younger skin and longer in mature adults, usually late 20s and older). This is where melanocytes exist and melanin is produced.

True or False: People of different races have approximately the same number of melanocytes. People with dark skin have melanocytes that are more active and produce more melanin.

True: The color of skin depends on the melanin produced.

What is the Malpighian Layer?

A layer made up of the stratum mucosum and stratum germinativum. The stratum mucosum is only a single cell layer above the stratum germinativum.

The Dermis, made up of connective tissue, is divided into what two layers?

1. The Papillary Layer

2. The Reticular Layer

Tell me about the Papillary Layer:

The strongest portion of the dermis, lies directly below the epidermis and is made of elastic collegenous and reticular fibers that are cone-shapes, finger-like projections called papillae.

Tell me about the Reticular Layer:

The thickest layer of the skin, is composed of dense bundles of collagen fibers. It includes numerous appendages: arrector pili muscles, blood vessels, fat cells, hair follicles, lymph vessels, nerve endings, sebaceous glands, and sudoriferous glands.

Name the sensation associated with the following:

1. End of Bulb Krause

2. Pacinian Corpuscle

3. Ruffini’s End Organ

4. Meissner’s Corpuscle

5. Merkel’s Disc

1. Cold

2. Pressure

3. Heat

4. Touch

5. Light Touch

What are these appendages (found in the reticular layer) responsible for?

1. Arrector Pili Muscle

2. Sebaceous Gland

3. Sudoriferous Gland

1. Goosebumps

2. Oil

3. Sweat

Lymph glands produce lymph, which is made of ? .

White blood corpuscles and plasma. HIV stores in lymph, as well as blood and other body fluids.

Where are sudoriferous glands (sweat) found?

Deep in the dermis, have tubular ducts extending all the way up to the pores in the epidermis.

Where are apocrine glands found?

The underarms (axillae) and genitals; believed to excrete pheromones which play a role in sexual attraction.

Where are eccrine glands found?

All over the body; increased number on the forehead, palms and soles of the feet. Excrete mainly water with a little bit of salt, urea, and water soluble substance. (Sweet Sweat)

True or False: The sebaceous glands vary in size and shape and in their production of a waxy, oily substance, called sebum, which lubricates the skin and hair.

True

Where are sebaceous glands found in greater numbers?

The scalp, T-Zone (forehead, nose, chin), and the cheeks

What influences hair growth at different ages in males and females?

Hormones and genetic inheritance

The root or papilla of the mature terminal hair is found in the ? , and the hair shaft reaches up to its ? .

lower part of the dermis; follicular opening in the epidermis

The arrector pili muscles is an appendage that is attached to ? .

The hair follicle; it is responsible for lifting the hair to trap a layer of air on the skin’s surface.

Tell me about the subcutaneous layer:

Also known as the subcutis or adipose tissue; a fatty layer at the base of the dermis. This layer varies in thickness depending on the individual’s sex, age, and overall health. Many of the arteries, veins, and lymphatic circulate through this area, as do nerve endings and an abundance of fat cells. This layer protects against impact, i.e. hits and falls.

Healthy ? is continually growing, shedding, and being replaced.

Hair

The hair sits in a ? in the skin.

Pocket / indentation / depression

The outer sheath of the follicular canal is formed from what?

Basal cell layer

The inner side of the follicular canal (external root sheath) is made up of what?

Horny Epidermal Tissue

True or False: The hair shaft is lined with epidermal tissue and in full-grown, active hair stage extends downward, through the dermis to the subcutaneous tissue.

True

What is responsible for producing the hair follicle and the hair matrix?

Epidermal Cells

The base of the follicular canal widens (enlarges) to something called the ? .

Hair Follicle Bulb

What is the area where the hair grows and contains the dividing cells of hair matrix?

The Bulb

What does the hair matrix do?

Produces the hair and the protective external and internal root sheath

What is the dermal papilla?

Located at the base of the hair bulb, it is an indentation which is the layer of dermal tissue that attaches itself to the epidermis with protrusions called papillae. These papillae contain the blood supply needed for providing nutrients for growth as well as hormones that stimulate hair growth.

True or False: The arrector pili muscle is an appendage to the hair follicle that is attached to the underside of the follicle, midway between the bulb and the sebaceous gland.

True

Which appendage is partially responsible for heat regulation?

Arrector Pili Muscle

What causes the arrector pili muscle fiber to contract, lifting the hair straight up and resulting in goosebumps?

Fear and cold stimuli

The sebaceous glands help prevent the epidermis from what?

Drying and cracking, and preventing bacteria and germs from entering the skin

What are the 3 layers of the hair from outer to inner most?

1. Cuticle

2. Cortex

3. Medulla

What is the cuticle layer of the hair?

The outermost layer composed of transparent cells that overlap like scales, its purpose is to protect the inner layers of the hair.

What is the cortex layer of the hair?

The middle layer of the hair made of elongated cells of fibrous tissue and pigment that gives hair its color. The cortex is also the layer that gives hair its strength and elasticity.

What is the medulla layer of the hair?

The innermost layer of the hair made of round cells, also known as the pith or marrow. Fine hair lacks the medulla, but the medulla can be found in wavy hair. Generally the curlier the hair, the stronger the medulla.

What are the three main types of hair?

1. Lanugo

2. Vellus

3. Terminal

What is lanugo hair?

Soft, downey hair, also called fetal hair because it is on fetuses in utero and on infants at birth, covering their bodies and scaps. Can have pigment - light or dark. It often sheds a few weeks after birth, eventually the permanent hair begins to grow in.

What is vellus hair?

Present through adulthood. It is fine, short, and often called “peach-fuzz”. Vellus hair often has no pigment or medulla. Women are believed to have 55% more vellus hair than men, it can be found of womens faces where men produce beard and mustache hair at puberty and onward.

What is terminal hair?

Longer, coarser, medullated and pigmented hair that covers the scalp and is found on the arms and legs of both males and females. At puberty, it is also found in the groin area and axillae of both males and females, as well as on the face, chest and back of men.

Growth of vellus and terminal hair is affected by what?

Age, genetics, health and the hormonal changes of puberty, pregnancy and menopause.

The three main stages of hair growth are:

1. Anagen

2. Catagen

3. Telogen

Tell me about the anagen phase:

The Growing Phase. The hair’s active growing phase, when the hair follicle is at its deepest. At this stage, the hair matrix is active, encapsulating the dermal papilla, and the bulb of the hair is visibly darker.

Once a growing anagen hair has reached its full length, it can remain there, depending on location for what varying amounts of time?

A few weeks on the fingers to eight years on the scalp.

Tell me about the catagen phase:

The Transitional Phase: Also known as the involution phase; the shortest hair-growth phase, lasting for only a few days to a few weeks. The hair follicle separates from the dermal papilla, the follicle shrinks to about a third of its anagen size. Club hair starts in this phase.

Tell me about the telogen phase:

The Resting Phase; the base of the hair looks like a club, hence the name club hair. The bulb is usually white. Telogen hairs increase (i.e. more hair loss) during illness, after child birth, and when an individual is experiencing stress.

Will excess androgens lead to a longer or shorter telogen phase?

Shorter telogen phase as they can stimulate terminal hair to regrow faster (anagen).

What are the multiple functions of the skin?

Protection, heat regulation, excretion, secretion, absorption, sensation, and the synthesis of vitamin D.

What should health skin have?

Hair

What is hair nourished by?

Blood and hormones

What are the percentages of anagen, telogen and catagen hair on the scalp?

Anagen: 85% (Duration of anagen; 2-6yrs)

Catagen: 1-2%

Telogen: 13%

What is the name for the skins built-in protective aid which has a pH of 5 to 5.6?

The acid mantle

The acid mantle is caused by the combined activity of what?

Sweat and sebaceous glands. Perspiration is acidic, as it lies on the skin’s surface it can act as a bactericide by inhibiting the growth of bacteria.

Unwanted organisms are recognized by ? in the epidermis that warn against invading microorganisms. ? are then released to engulf and destroy the invading organisms.

Langerhans’ Cells (Immunologic function); Leukocytes

True or False: The adipose tissue provides a source of energy.

True

A healthy body temperature is usually around what?

98 degrees F; 37 degrees C

Evaporation of perspiration of the skins surface produces cooling, also known as?

Thermoregulation

True or False: The skin can absorb oil and fat based substances to differing levels but it cannot absorb water.

True

What is the most common skin cancer vs. the most dangerous (can be deadly)?

Most common = Basal Cell Carcinoma

Most deadly = Malignant Melanoma

The bacteria killing/inhibiting layer made of sweat and lipids (fat); Built in protective aid, with a pH of 5 to 5.6. Caused by the combined activity of the sweat and sebaceous glands. Perspiration is acidic, as it lies on the skins surface it acts as a bactericide.

Acid Mantle

Also known as: Hypodermis, Subcutis, or subcutaneous layer; Connective tissue in animal bodies that contains fat, it is a layer of fat that provides insulation, cushioning, and energy storage.

Adipose Tissue

Glands in the axillae (underarm) and groin (genitals/pubic/triangle region) that secrete sweat and substances that produce body odor when contaminated with bacteria.

Apocrine Glands

A small muscle/appendage attached to hair follicles that causes hair to stand upright when contracted, often referred to as "goosebumps."

Arrector Pili Muscle

The deepest layer of the epidermis where new skin cells are generated - living layer of dividing cells that continuously change and push upward, consisting of the Stratum Spinosum and Stratum Germinativum.

Basal Zone

The thick layer of skin beneath the epidermis, composed of connective tissue, blood vessels, and nerve endings, providing structural support and housing various skin appendages. Contains the papillary layer and the reticular layer, which contribute to the skin's strength and elasticity.

Dermis

The process of shedding dead skin cells from the outermost layer of the skin, exfoliation.

Desquamation

Sweat glands found throughout the skin, that excrete mainly water and salt.

Eccrine Glands

A translucent/clear intracellular protein found in the stratum lucidum of the skin, involved in the process of keratinization.

Eleidin

Also Known As: Cuticle, Scarf, No Blood, Epithelial Tissue

The thin (0.05-1.5mm) outermost layer of skin, providing a protective barrier and containing several sub-layers, including the stratum corneum and stratum lucidum, stratum granulosum, stratum spinosum, stratum germinativum. CLGSG (Come Let’s Get Sunburned, Girls)

Epidermis (CLGSG)

The tissue that forms a thin protective layer on bodily structures.

Epithelial Tissue

The inner side of the follicular canal which is made of horny epidermal tissue.

External Root Sheeth

The depression or indentation in the skin that houses the entire pilosebaceous unit

Follicular Canal

The layer of skin where cells divide

Germinal Zone

The outermost portion of the epidermis

Horny Zone

The skin and its accessory organs, such as the sebaceous and sweat glands, sensory receptors, hair and nails

Integumentary System

A protein found in the skin that helps guard against invasion

Keratin

The change of living cells to dead ones

Keratinization

Cells found in the epidermis that warn against the invasion of microorganisms and respond to that invasion; immunologic function. Derived from bone marrow and constitute about 5% of cells within the epidermis.

Langerhans’ Cells

Colorless, watery fluid that circulates through the lymphatic system; similar in composition to blood plasma

Lymph

A skin layer made of the stratum mucosum and stratum germinativum

Malpighian Layer

Nerve endings in the skin that are sensitive to touch

Meissner’s Corpuscles

Grains of pigment that give your hair and skin color

Melanin