Chapter 4Skin and Body Membranes

“The Dermis”

F. DermisF. Dermis1.Papillary layer

Projections called dermal papillae Pain receptors Capillary loops

2. Reticular layer Blood vessels Glands Nerve receptors

Nerve ReceptorsNerve Receptors

Free nerve endings

• detect temp, mechanical stimuli (such as pressure), pain, & touch

Meissner’s corpuscles

• Tactile, light touch, found in abundance in fingertips, palms, soles, lips, tongue, face, genitals. In dermal papillae.

Pacinian corpuscles

• Deep, pressure, adaptive

G. Normal Skin Color DeterminantsG. Normal Skin Color Determinants1. Melanin

a. Yellow, brown or black pigment

b. Pigment produced by melanocytes

c. Melanocytes are mostly in the stratum germinativum

d. Amount of melanin produced depends upon genetics and exposure to sunlight

2. Carotene

a. Orange-yellow pigment from some vegetables

3. Hemoglobin

a. Red coloring from blood cells in dermis capillaries

b. Oxygen content determines the extent of red coloring

G. MelaninG. Melanin

H. Appendages of the SkinH. Appendages of the Skin

1.Sebaceous glands

a. Produce oil

- Lubricant for skin

- Kills bacteria

b. Most with ducts that empty into hair follicles

c. Glands are activated at puberty

H. Appendages of the SkinH. Appendages of the Skin

2. Sweat glands

a. Widely distributed in skin

b. Two types

Eccrine

Open via duct to pore on skin surface

Apocrine

Ducts empty into hair follicles

c. Sweat and Its Functionc. Sweat and Its Function

i. Composition Mostly water Some metabolic waste Fatty acids and proteins (apocrine only)

ii. Function

• Helps dissipate excess heat

• Excretes waste products

• Acidic nature inhibits bacteria growth

iii. Odor is from associated bacteria

H. Appendages of the SkinH. Appendages of the Skin

3. Hair

a. Produced by hair bulb

b. Consists of hard keratinized epithelial cells

c. Melanocytes provide pigment for hair color Figure 4.7c

d. Hair Anatomyd. Hair Anatomy

i. Central medulla

ii. Cortex surrounds medulla

iii. Cuticle on outside of cortex

-Most heavily keratinized

e. Associated Hair Structurese. Associated Hair Structures

i. Hair follicle

Dermal and epidermal sheath surround hair root

ii. Arrector pilli

Smooth muscle

Goose bumps

iii. Sebaceous gland

iv. Sweat gland

Appendages of the SkinAppendages of the Skin

4. Nails

a. Scale-like modifications of the epidermis

Heavily keratinized

b. Stratum basale extends beneath the nail bed

Responsible for growth

c. Lack of pigment makes them colorless