Bio Exam 2 Part 2

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Integumentary System

The Dermis, Hypodermis and Accessory Structures Part 2

Dermis

Between epidermis and hypodermis Gives structural strength Contains nerves, blood vessels, hair follicles, smooth muscles, glands, and lymphatic vessels. Sensory function : pain, itch, tickle, temperature, touch, pressure. Two layers : Papillary layer and Reticular Layer

Papillary Layer

Named for dermal papillae Attaches the epidermis to dermis Nourishes the epidermis Consists of areolar tissue Contains : capillaries, lymphatic capillaries, sensory neurons

Reticular Layer

Meshwork of dense irregular connective tissue Collagen fibers Elastin fibers Contains : capillaries, lymphatic capillaries, sensory neurons, sweat glands and hair follicles

Lines of Cleavage

Formed by arrangement of collagen and elastin fibers in the skin For surgery and wound healing Parallel cut, better healing and less scarring Perpendicular cut, remain open and more scarring

Hypodermis

Separates skin from deeper structures Stabilizes skin to underlying tissue Allows independent movement Dominated by adipose tissue Storage of energy

Review

1. Describe the location of the dermis.

2. What type of tissue comprises the epidermis?

3. Where are the capillaries and sensory neurons that supply the epidermis located?

4. What accounts for the ability of the dermis to undergo repeated stretching?

5. What is the function of the hypodermis?

6. Liposuction is a surgical procedure to remove which layer?

7. What would occur if you cut against the cleavage lines?

8. Where is the papillary layer located and what tissue does it contain?

Answers for Review

1. X

2. X

3. X

4. X

5. X

6. X

7. X

Accessory Structures

Sensory Receptors - monitor external environment Hair and hair follicles - Produce hairs that protect skull and provide touch sensations Exocrine sweat glands - Thermoregulation, remove waste, lubricate epidermis Nails - protect and support tips of fingers and toes

Skin Sensory Receptors

Epidermis Merkel cells in deep layers Monitored by tactile discs Free nerve endings for pain and temp Dermis More specialized receptors than epidermis Light touch (Tactile corpuscles) Deep pressure

Hair

Found everywhere except palms, soles, side of fingers,toes, lips, and external genitalia Body has 2.5 million hairs (75% on body not including head) Two types - Terminal hairs (large, head, armpits, groin) and vellus hairs (small, body surface)

Hair follicle

Forms a single hair Composed of epithelial and connective tissues Two parts - Hair shaft (exposed but extends into follicle) and hair root (anchoring portion where growth occurs)

Accessory hair structures

Root hair plexus - sensory nerves surrounding base of follicle Arrector pili muscle - smooth muscle that pulls on follicle causing hair to stand erect (goosebumps)

Layers of the follicle

Internal root sheath - surrounds hair root External root sheath - entire length of follicle Glassy membrane - thick, clear, basal lamina Base has hair bulb and hair papilla

Layers of hair shaft

Cuticle - outermost layer made of keratin Cortex - middle layer with hard keratin for stiffness Medulla - core with flexible soft keratin

Hair growth cycle

2-5 years at 0.33mm

Hair color

Differences in structure and variation in pigments produced in melanocytes at hair papilla Pigment production decreases with age

Review

Describe a typical strand of hair. What happens when an arrector pili muscle contracts? Why is pulling a hair painful, yet cutting a hair is not?

Answers for review

X X X

Sebaceous glands

Holocrine glands that discharge on oily lipid secretion Secrete onto one hair follicle Releases sebum onto follicle and skin surface Sebum Mixture of triglycerides, cholesterol, proteins, and electrolytes Lubricates hair shaft and is antimicrobial

Sweat glands

Produces watery secretion by merocrine secretion Myoepithelial cells (washes epidermal surface) Two Types eccrine

Apocrine sweat glands

Limited distribution Produce viscous secretion Influenced by hormones Has ceruminous glands and mammary glands

Eccrine

Merocrine sweat glands

Nails

Protect exposed dorsal surfaces (tips of fingers and toes) Help limit distortion Composed of dead cells packed with keratin Can be affected by conditions that alter body metabolism

Nail structure

Nail body lateral nail grooves and nail folds Covers nail bed lunula (pale) Nail root - epidermal fold where nail production occurs

Structures associated with nails

Eponychium Portion of stratum corneum of nail root extending over nail Known as cuticle Hyponychium Area of thickened stratum corneum under free edge

Age related changes in skin

Fewer melanocytes Thinning epidermis Diminished immune response Thinning dermis Reduced blood supply Slower skin repair

Review

1. Identify two types of exocrine glands found in the skin.
2. What are the functions of sebaceous secretions?
3. Deodorants are used to mask the effects of secretions from which type of skin gland?
4. Define hyponychium.
5. Describe a typical fingernail.
6. Where does nail production occur?
7. Identify some common effects of the aging process on skin.
8. Why does hair turn white or gray with age?
9. Why do individuals tolerate summer heat less well and become more susceptible to heat-related illness when they become older?

Answers for Review