Integumentary System P.2

Adipose Connective Tissue

Description:

• Loose connective tissue composed primarily of adipocytes (fat cells)

Function:

• Primary long-term energy reserve for body

• Insulation

• Support and protection for organs and tissues

Arrector pili m.

Location:

• Dermis of thin skin

Description:

• Bundles of smooth muscle fibers

• Stretches obliquely from papillary layer of dermis to hair follicle

• Innervated by adrenergic nerve fibers

Function:

• Contraction causes hair to stand in more vertical position (hair "stands on end")

• Elevates epidermis around opening of hair follicle ("goose bumps")

• Assists in secretion from sebaceous gland

Arterial blood vessels of skin

Location:

• Dermis of skin

Description:

• Dense network of arterial blood vessels in the dermis

• Larger vessels are near where the reticular layer of dermis intersects the subcutaneous (hypodermis) layer

Function:

• Supply arterial blood to epidermis, dermis and all structures in dermis

Free nerve ending of skin

Location:

• Epidermis and papillary layer of dermis

Description:

• The dendritic endings of sensory neurons

Function:

• Detect temperature and pain

Lamellar corpuscles

Location:

• Reticular layer of dermis of skin

Description:

• Large oval, sensory receptors encapsulated by neurolemmocytes and connective tissue

• Found deep in reticular layer of dermis; subcutaneous tissue of palms of hands, soles of feet, and external genitalia; synovial membranes of joints; and walls of some organs

Function:

• Detect coarse touch and deep pressure

Comment:

• Formerly called Pacinian corpuscles

Root hair plexus

Location:

• Reticular layer of dermis

Description:

• The dendritic endings of sensory neurons that surround hair follicles

Function:

• Detect hair movements

Tactile corpuscles

Location:

• Dermal papilla of skin

Description:

• Large oval, encapsulated sensory receptors

• Found in dermal papilla of skin where there is not hair: fingertips, palm of hand, eyelids, lips, nipples and genitals

Function:

• Detect discriminative touch for textures and shapes, light touch

Comment:

• Formerly called Meissner corpuscles

Venous blood vessels of skin

Location:

• Dermis of skin

Description:

• Dense network of venous blood vessels in the dermis

• Larger vessels are near where the reticular layer of dermis intersects the subcutaneous (hypodermis) layer

Function:

• Drain venous blood from epidermis, dermis and all structures in dermis

Hair shaft

Location:

• Surface of epidermis

Description:

• Filamentous, pigmented, keratinized structure

• Projects from epidermal surface, i.e., extends beyond skin surface (length varies by body region)

Function:

• Protection (e.g., from sunburn)

• Heat retention (esp. on scalp)

• Cutaneous sensation

• Dispersion of chemical signals

• Facial recognition/visual identification

Keratinocyte

Location:

• Skin

Description:

• Predominant cell of epidermis

• Originates in basal layer of epidermis and differentiates as they migrate toward surface of skin

• Fully differentiated keratinocyte composed of 85% keratin

Function:

• Helps form epidermal barrier to water and dehydration

Connective tissue sheath

Location:

• Dermis of thin skin

• Surrounds hair follicle

Description:

• Dense irregular connective tissue

Function:

• Supports hair follicle

Cortex of hair

Location:

• Hair

Description:

• Located external to medulla (core) of hair

• Contains several layers of compact, flattened cells

• Cells undergo differentiation into keratin-filled cells

Function:

• Primary source of hard keratin for hair

• Hair stiffness related to hard keratin

Comment:

• Layers of hair include (deep to superficial): medulla (if present), cortex, and cuticle

Differentiation zone of hair 

Location:

• Hair root

Description:

• Zone of dividing cells in core of hair root

Function:

• Site for differentiation of cells in hair root

External root sheath

Location:

• Hair follicle

Description:

• Downgrowth of epidermis that forms external layer of hair follicle

• At skin surface composed of all layers of epidermis

• Thinner at dermal papilla, where it is composed only of cells corresponding to stratum Basale of epidermis

Function:

• Support for hair production and growth

Glassy membrane

Location:

• Dermis of thin skin

Description:

• Thickened basal lamina between dermis and hair follicle

Function:

• Barrier between dermis and hair follicle

• Structural support for hair follicle

Hair matrix

Location:

• Hair bulb

Description:

• Surrounds dermal papilla of hair bulb

• Scattered melanocytes present in matrix

Function:

• Zone of dividing cells that give rise to all layers of hair and hair follicle

• Division and proliferation of cells in matrix account for hair growth

Internal root sheath

Location:

• Hair follicle

Description:

• Multicellular sheath that surrounds hair

• Extends around inferior part of hair

• Separates hair from external root sheath

• Comprised of soft keratin

Function:

• Support for hair production and growth

Dense irregular connective tissue

The dermis is the layer just deep to the epidermis. You will find blood vessels, nerves, hair, follicles, and glades of the skin. Comprised of dense irregular connective tissue that gives the ability to resist tensile forces in all directions.

Papillary layer

Name due to the wave-like protrusions toward the epidermis called dermal papillae.

Epidermal ridges

Those ridges help keep the epidermis attached to the dermis, also provide traction that helps to prevent objects slipping out of our hands when holding them. 

Sudoriferous Glands

Also known as sweat glands and produce sweat.

What are the two different types of sweat glands?

Eccrine glands- Temperature regulation - Found throughout the body

Apocrine Glands- Inactive until puberty - Milky, odorant sweat released into hair follicle - Only found in axillary, pubic, anal, and areolar regions.

Sebaceous Glands

Oily secretion released onto the surface of the skin and into hair follicles. Prevents water loss from hair and skin. Absent in palms, soles, fingertips. and toes.

Ceruminous Glands

Only found in ear canal, secrete a waxy substance that combines with sebum and exfoliated called to create cerumen also known as earwax.

Waterproofs the ear canal

Resists infections

Keeps eardrum pliable

Mammary Glands

Modified apocrine sweat glands, found only in breasts, produce milk

Sebaceous gland 

Location:

• Skin

Description:

• Simple, saccular holocrine gland

• Secretory part lies in dermis

• Duct opens into hair follicle or onto skin surface

Function:

• Secrete sebum (oily substance)

• Lubricate and waterproof hair shaft

Comment:

• Not found in skin of palms (hands) or soles (feet)

• Holocrine glands produce secretion through fatty degeneration of cells in secretory part of gland

Duct of merocrine sweat gland

Location:

• Dermis and epidermis of skin

Description:

• Lined by stratified cuboidal epithelium

• Has spiral course through dermis and epidermis from secretory part of gland

• Cells of duct epithelium are smaller and duct has a smaller lumen than secretory part of gland

Comment:

• Sweat from merocrine gland is a nonviscous, hypotonic watery secretion

Merocrine sweat gland

Location:

• Dermis and hypodermis of skin

Description:

• Simple, coiled, tubular gland

• Secretory part of gland composed of simple cuboidal epithelium

• Duct opens directly on surface of skin at sweat pore

• Innervated by cholinergic nerve fibers

Function:

• Production and release of non-viscous, hypotonic, watery secretion known as sweat

• Plays a major role in temperature regulation through cooling that results from evaporation of sweat from body surface

Duct of apocrine sweat gland 

Location:

• Thin skin of axilla, areola of nipple, and anal region

• Embedded in dermis and hypodermis

Description:

• Duct of apocrine gland opens into hair follicle usually just superficial to opening of sebaceous gland duct

• Simple coiled tubular gland with large lumen

Basal cell of sebaceous gland

Location:

• Along periphery of secretory part of sebaceous gland

Description:

• Squamous epithelial cell lining basal lamina of sebaceous gland

Function:

• Have potential to undergo cell division to replenish basal cell population

• May differentiate into secretory cell

Duct of sebaceous gland

Location:

• Dermis and epidermis of thin skin

Description:

• Short passage between secretory part of gland and hair follicle

• Lined by stratified squamous epithelium that is continuous with external root sheath of hair

• Most frequently opens into upper portion of hair follicle

• May open directly on skin surface of glans penis, clitoris, and lips

Hair follicle

Location:

• Dermis

• May extend into hypodermis

Description:

• Tube that surrounds hair root

• Courses obliquely through dermis

• Two coats: epidermic (inner) and dermic (outer)

• Characteristic parts include: dermal papilla bulb, hair shaft, cuticle layer, internal follicular sheath, and external follicular sheath

• Associated with hair receptors and arrector muscle of the hair

Function:

• Hair formation and growth

Sebaceous gland

Location:

• Skin

Description:

• Simple, saccular holocrine gland

• Secretory part lies in dermis

• Duct opens into hair follicle or onto skin surface

Function:

• Secrete sebum (oily substance)

• Lubricate and waterproof hair shaft

Secretory cell of sebaceous glands

Location:

• Secretory part of sebaceous gland located in dermis

Description:

• Form acini of gland

• Differentiates from basal cells and then proliferates and migrates toward duct

• Contain increasing amounts of lipid droplets in cytoplasm during maturation

• Release sebum by holocrine process (cell membrane ruptures releasing cell contents and cellular debris)

Function:

• Produce and release sebum into duct of gland

Basal Lamin of merocrine sweat gland

Location:

• Periphery of secretory part of merocrine sweat gland

Description:

• Layer of electron dense matrix between epithelium and adjacent connective tissue

Function:

• Provides support for epithelial cells of secretory part of merocrine sweat gland

Epithelial cell of merocrine sweat gland

Location:

• Secretory part of merocrine gland

Description:

• Pseudostratified epithelium

• Two types of secretory cells, dark and clear, each contribute components sweat by exocytosis from luminal surface

• In contact with myoepithelial cells along basal surface

Function:

• Production of nonviscous, hypotonic, watery secretion known as sweat

Lumen of merocrine sweat gland

Location:

• Merocrine sweat gland

Description:

• Opening in secretory part of gland

• Surrounded by secretory epithelial cells

Function:

• Receives secretions from epithelial cells that compose merocrine sweat

Merocrine sweat gland

Location:

• Dermis and hypodermis of skin

Description:

• Simple, coiled, tubular gland

• Secretory part of gland composed of simple cuboidal epithelium

• Duct opens directly on surface of skin at sweat pore

• Innervated by cholinergic nerve fibers

Function:

• Production and release of non-viscous, hypotonic, watery secretion known as sweat

• Plays a major role in temperature regulation through cooling that results from evaporation of sweat from body surface

Myoepithelial cell of merocrine sweat gland

Location:

• Secretory part of apocrine sweat gland

• Between secretory cell and basal lamina

Description:

• Epithelial cell

Function:

• Contraction assists in release of fluid (sweat) from gland