The Skin “The Players in the Layers”

Introduction Structure Epidermis Dermis Subcutaneous Layer – Fat Layer

Functions of the Skin Protection – barrier to disease Temperature regulation Sensations – touch Excretion of wastes - water Determines characteristics – skin colour, markings

The Skin FG04_02.JPG Title: Components of the Integumentary System Notes: Relationships among the major components of the integumentary system (with the exception of nails, shown in Figure 4-15). Keywords: integumentary system, cutaneous, epidermis, dermis, papillary layer, reticular layer, hair follicles, exocrine glands, nails

Epidermis Layers of flat squished cells – like the tiles on your roof Over most of the body it’s thin – like a piece of paper Approximately every month we shed entire skin surface (28 days)

Epidermis FG04_03.JPG Title: The Structure of the Epidermis Notes: A light micrograph through a portion of the epidermis, shows the major stratified layers of epidermal cells. Keywords: epidermis, structure, layers, stratum corneum, stratum lucidum, stratum granulosum, stratum spinosum, stratum germinativum, dermis

Replacement of Epidermal Cells Base of epidermis New cells are pushed toward surface New epidermal cells produce keratin Cells are flattened as they are pushed upwards Cells die Outermost layer Cells are dead, filled with keratin Takes about two weeks for an epidermal cell to move from the bottom layer to the top

Pigments Humans have a pigment known as melanin in their skin. Melanin is produced by cells called melanocytes. Melanin is responsible for the color of our skin tone and can provide some protection from UV rays.

Melanocytes and Melanin FG04_06A.JPG Title: Melanocytes Notes: The micrograph and accompanying draiwing indicate the location and orientation of melanocytes in the stratum germinavatum. Keywords: melanocytes, stratum germinavatum, melanin, basement membrane

Melanocytes and Melanin FG04_06B.JPG Title: Melanocytes Notes: The micrograph and accompanying draiwing indicate the location and orientation of melanocytes in the stratum germinavatum. Keywords: melanocytes, stratum germinavatum, melanin, basement membrane

Epidermis and Dermis Epidermis has low blood supply Dermis has lots of blood Epidermis receives nourishment from dermis Cells far away from nourishment die

Dermis Largest part of the skin Connective tissue Contains Blood vessels Nerves Glands Hair follicles

Papillary Layer of the Dermis Outermost layer of the dermis Surface area increased by papillae Little Grooves Form fingerprints Has lots of sensory receptors Papillary Layer

Deeper Layer of the Dermis Dense connective tissue Contains Blood vessels Glands Deep pressure receptors Attached to underlying organs by the subcutaneous layer

Subcutaneous Layer Loose connective tissue Packed with fat cells Stabilizes position of skin

Epidermal Parts Hair Glands Nails

Functions of Hair Protection Thermoregulation Sensory Minor role in humans

Hair Structure Shaft Above the surface of the skin Root Below the surface

Hair Structure Medulla Soft core of hair Cortex Hard core that gives hair its stiffness Cuticle Outermost layer of hair

Hair Structure FG04_10A.JPG Title: Hair Follicles Notes: Hairs originate in complex organs termed follicles. (a) A longitudinal section and a cross section through a hair follicle. (b) and (c) A section along the longitudinal axis of a hair follicle. Keywords: hair follicle, longitudinal section, cross section, sebaceous gland, arrectory pili muscle, cortex, cuticle, internal root sheath, connective tissue layer, glassy membrane, external root shaft

Arrector Pili Smooth muscle attaches to follicle Raises hairs Response to fright or cold Function?

Glands Sebaceous glands Connected to hair follicles Secrete a waxy, oily substance (sebum) Secretion increases at puberty

Sebaceous Glands FG04_13A.JPG Title: Sebaceous Glands and Follicles Notes: The structure of sebaceous glands and sebaceous follicles in the skin. Keywords: sebaceous glands, sebaceous follicles, structure, sebum, germinative cells

Glands Sweat glands Found just about everywhere Produce “perspiration” Water, salt, and metabolic wastes. Function – cooling of the body

Glands Scent Glands Specific type of sweat gland Found near hair follicles Auxiliary & genital regions Develop at puberty

Nails Dorsal surfaces of ends of fingers & toes Primate feature Grasping

Nail Structure Nail body Free edge Nail root Matrix Lunula (moon)

Nail Structure FG04_15.JPG Title: Structure of a Nail Notes: These drawings illustrate the prominent features of a typical fingernail as view from the surface and in section. Keywords: fingernail, hyponychium, nail bed, lateral nail groove, lunula, eponychium, phalanx, dermis, epidermis