LAB 13: Skin Structure and Function

�  Complete lab 13 in your lab book using the slides on the following pages

�  Begin by identifying the hypodermis (subcutaneous region), dermis and epidermis on figure 5.1 (pg. 151) in your text book. Then identify those same regions on the slide provided in this supplement.

�  Once you can recognize and name those regions on the slide, move through the slides in this supplement and identify all of the structures listed in sections 1a, b and c, section 2a and b, and section 3a, b and c on pages 68 and 69 of the lab book.

�  Identify and name the structures on the skin diagram on page 68 of your lab book.

�  Answer the questions on pages 70-71 in your lab.

SKIN REGIONS

Dermis: holds the majority of

accessory structures (nerve

endings, hair follicles,

sebaceous glands)

Epidermis: keratinized stratified squamous E.T.

Hypodermis (subcutaneous region): abundant adipose tissue. Technically not a skin region- (hypo= below, cutaneous=skin)

EPIDERMIS: THICK SKIN (Palms of the hands and soles of the feet: 5 layers)

Stratum Corneum: Many layers of dead, keratinized cells provides waterproofing and protection from abrasion and penetration Stratum

Lucidum: A thin, clear layer of dead keratinocytes found only in thick skin

Stratum spinosum: Many layers of living cells that may store melanin granules

Stratum basale: Cuboidal looking mitotic layer adjacent to the dermis below.

Stratum Granulosum

Stratum granulosum: dark purple granules are visible containing keratin (contribute to hardness and waterproofing)

EPIDERMIS: THICK SKIN (Palms of the hands and soles of the feet: 5 layers)

Melanocytes: produce the dark pigment melanin which is stored in granules by keratinocytes throughout the epidermis Melanin provides protection from UV light Notice the white space surrounding the cells making them easy to identify

EPIDERMIS: THIN SKIN (4 layers: no stratum lucidum)

Dermal papillae: small hills of dermis pushing upward into the epidermis

Epidermal pegs: folds of epidermis pushing down into the dermis

MEISSNER’S CORPUSCLE

Meissner’s corpuscle: The “pink tornado” looking specialized nerve ending providing discriminative touch (such as being able to recognize a penny in your pocket just from feeling it)

REGIONS OF THE DERMIS (Papillary and Reticular) The Dermis: as you know is

made up of Dense Irregular C.T. It is very vascular and filled with many accessory structures you will see on the following pages. There are two distinct regions within the dermis: the papillary and reticular layers.

The Reticular Layer: Thick collagen swirls are visible. This is the largest layer of the dermis.

The Papillary Layer: Notice the thin, fine collagen fibers compared to the reticular layer below. This layer is very vascular as it supplies the epidermis. Meissner’s corpuscles may be found here in the dermal papillae.

Papillary layer

Reticular layer

SEBACEOUS GLANDS Sebaceous Glands: appear as ‘foamy’ bags. They are generally associated with hair follicles and produce oily sebum to soften and lubricate skin and hair. These are found all over the body except in thick skin (palms and soles). Sebaceous glands are holocrine glands. As you might recall, this means the cells produce lipids (for sebum) until they rupture, releasing their their product into a hair follicle or skin pore. Reticular layer

SUDORIFEROUS GLANDS (Sweat Glands) Sudoriferous Glands:

(within the brackets) Notice the distinct rings of cuboidal cells forming the ducts of these glands. This will help you to distinguish them from sebaceous glands. There are two types of sweat glands in the body: Eccrine sudoriferous glands are the most numerous and release watery ‘sweat’ to the surface of the skin to prevent overheating.

Apocrine sudoriferous glands are larger and found mainly in the axillary and genital areas. These don’t begin functioning until puberty, releasing a secretion containing fats and proteins. This secretion has no role in thermoregulation so may be a type of pheromone or ‘sexual scent’. (Yes! But don’t leave sweat to become odorous thinking you will attract the opposite sex J)

SEBACOUS VS. SUDORIFEROUS?

Just in case you are having a hard time distinguishing oil glands (sebaceous) from sweat glands (sudoriferous), This picture shows both side-by-side for easy

Sudoriferous gland

Sebaceous gland

HAIR FOLLICLES Hair follicles: (within the

brackets) New hair cells form down at the deep end of the follicle where a capillary tuft called a papilla supplies nutrients and oxygen to the growing hair. By the time hair reaches the skin surface it is now dead, keratinized cells (they are too far from their nutrient source to be living). Nerve endings wrap around the base of each plexus providing sensitivity if hair is moved or pulled.

Papilla

Hair shaft

ARRECTOR PILI MUSCLES

Arrector pili muscles: (within the brackets) Are bundles of smooth muscle associated with hair follicles. Contraction of these muscles make the hairs ‘stand up’ creating a layer of air insulation for heat retention. As humans, we have evolved to have less hair. Our arrector pili muscles still function but do little to provide insulation. The result of our arrector pili muscles in action is formation of ‘goose bumps’.

Arrector Pili Muscles

Hair shaft

HYPODERMIS (Subcutaneous region)

Hypodermis: (within the brackets) Is not technically part of the skin. It is deep to the skin and anchors the skin to underlying structures (mainly muscle). Composed mainly of adipose C.T., it serves to insulate (to reduce heat loss) and serve as a shock absorber.

Hypodermis

HYPODERMIS (Subcutaneous region)

Pacinian (Lamellar) Corpuscles: (within the brackets) Originally called Pacinian corpuscles but renamed in your newer texts to Lamellar corpuscles. They resemble ‘sliced onions’. These sensory receptors detect pressure (such as when you are bumped) but do not provide discriminative touch. They are found in the deep dermis and hypodermis of the skin but can also be found internally detecting visceral pressure (such as in the pancreas).

Pacinian (Lamellar) Corpuscles

Notice the rings of purple cuboidal cells in the top left of the photo. Can you identify that structure?