The Integumentary System Lab Exercise 7 The Integumentary System Portland Community College BI 231

Skin Or Cutaneous membrane is an organ. (an organ is a structure that contains two or more of the primary tissue types) Embedded within the skin are various accessory structures the combination of both is called the integumentary system

Skin Epidermis: Superficial layer Made of stratified squamous keratinized epithelium 4-5 Layers Dermis: Underlying connective tissue layer 2 Layers Hypodermis: Not part of the skin, it is deep to the dermis Primarily adipose tissue

Layers of the epidermis Stratum basale: single row of cells Adjacent to the dermis and attached by the basement membrane. Constantly dividing and pushing up layers Melanocytes with melanin protects the skin from UV radiation

Layers of the Epidermis Stratum spinosum: several cell layers superficial to stratum basale. Cells also dividing Cells contain bundles of intermediate filaments made of pre-keratin Cells appear star-shaped because the cell membrane pulls away from the other cells, except in areas where desmosomes are.

Layers of the Epidermis Stratum granulosum: The upper part of this layer has cells that are beginning to die Lamellated granules contain a waterproofing glycolipid that is secreted into the extracellular space Keratohyaline granules combine with intermediate filaments to form keratin fibrils

Layers of the Epidermis Stratum lucidum: Thin translucent layer of dead keratinocytes Found only in thick skin

Layers of the Epidermis Stratum corneum: Outermost layer 20-30 cell layers thick Cells are dead and flattened Full of keratin Constantly being rubbed off

Epidermis cell phases Deepest layer (basale) goes through rapid division. Middle layers undergo a process of producing precursor molecules that lead to waterproofing of the cells. The final phase is the completion of the waterproofing process. Cells eventually die, providing a tough barrier

Dermis The dermis is the connective tissue layer under the epidermis. Composed of primarily of fibers: Irregularly arranged collagen fibers make up the majority and provide strength and flexibility to skin Lesser numbers of elastic fibers which provided elasticity to the skin There are also reticular fibers found in the dermis blood vessels, nerves, sensory receptors, hair follicles and glands.

Dermis Papillary Layer: Superficial dermal region Areolar connective tissue Contains capillaries, lymphatics and sensory neurons Dermal Papillae: the fingerlike projections from the superior surface Epidermal ridge: The epidermal layer that dips down into the dermal papillae Create fingerprints

Epidermis Epidermal ridge Papillary Layer Dermal Papillae Reticular Layer

Finger Prints Epidermal Ridge

Dermis Reticular Layer: Deepest skin layer Dense irregular connective tissue Contains the arteries, veins, sweat and sebaceous glands Cleavage lines: the deep creases (like in the palm) where collagen and elastic fibers are arranged in parallel bundles.

Hypodermis Subcutaneous layer that is not part of the skin Beneath the dermis layer Composed of adipose and areolar connective tissue Highly vascular Hypodermis

Cells of the Epidermis Keratinocytes: The main cells of the epidermis Produce keratin, water proof protein As new cells form, they push the older cells toward the surface, where they gradually accumulate keratin and eventually die Melanocytes: Spidery black cells In stratum basale Produce melanin, the pigment that protects skin from UV damage

Cells of the Epidermis

Meissner’s (Tactile) Corpuscle Located in the dermal papillae Receptor for light touch

Merkel Cells Merkel Cells: At the junction of the sensory nerve endings In upper dermis and ll lower epidermis Light touch (like fly walking over cheek)

Pacinian (Lamellated) Corpuscle Lie deep in the dermis Respond only when deep pressure is first applied Monitor high frequency vibrations

Other skin receptors Warm and cool receptors: When you are at comportable temperature both of these are firing If you increase or decrease the skin temperature beyond the range of these receptors, pain receptors are stimulated. Pain receptors are naked nerve endings in the dermis that respond to numerous environmental stimuli.

Integumentary Glands Sudoriferous (sweat) glands Lactiferous (milk) glands Sebaceous (oil) glands Ceruminous (earwax) glands

Eccrine (Merocrine) Sweat Glands Eccrine sweat glands Ducts open directly on the surface of the epidermis Produce normal body perspiration. Reduces body temperature by evaporative cooling

Apocrine Sweat Glands Apocrine glands: secrete a water and a higher concentration of organic acids than eccrine glands that bacteria can use for nutrients (creates body odor) Found in the armpits, around nipples and in the pubic region Secrete products into hair follicles or directly onto the surface. Begin functioning at puberty

Apocrine Sweat Glands Red arrow - Apocrine Sweat Glands Green arrow - Hair follicle

Sebaceous Glands Sebaceous glands Produce oily substance called sebum Helps waterproof the skin Acne: infection of the sebaceous gland

Hair Keratinized cells produced in Hair follicles: tubular compartments that contain hair(projections of the epidermis into dermis)

Hair Bulb: deepest portion of the hair follicle Bulb contains the hair matrix which contains actively dividing cells The actively dividing cells give rise to the hair root. As hair root approaches the surface of the skin it becomes the hair shaft. Hard Keratin covers the hair

Hair Histology

Arrector Pili Muscle Arrector pili muscle: Smooth muscle that pull hair upright during fright or cold (goose bumps)

Hair Determinate hair grows to a specific length and then stops Found in axilla, groin, eyelashes and eyebrows. Indeterminate hair grows without regard to length. Found on scalp and beards

Hair Medulla central portion of the hair which is enclosed by an outer cortex. The cortex may contain pigments which give the hair its color (melanin) The cuticle is superficial to the cortex

Fingernails Scale like modification of the epidermis Free edge: part that grows away from the finger Body: The nail Root: Embedded in skin and sticks to the nail bed Nail Bed: Extension of the stratum basale beneath the nail Nail Matrix: Proximal part of the nail bed responsible for nail growth Lunula: white crescent area; Most active growth region of nail matrix

Fingernail Structures

Muscle Tissue Like epithelial tissue, muscular tissue is a cellular tissue with the tissue having mostly cells and little matrix There are three types of muscle: skeletal, cardiac and smooth

Skeletal Muscle Cells called fibers Striated Voluntary Multinucleate

Sarcomere

Cardiac Muscle Striated but striations are much less obvious. Cardiac muscle cells are called myocytes. Branched Involuntary Intercalated discs, which facilitate the transmission of the electrical impulses in the heart

Smooth Muscle Nonstriated Involuntary Cells of smooth muscle are spindle-shaped Found in intestine where it propels food along by a process known as peristalsis and segmentation

The End The End