Integumentary System

Integumentary System Epidermis (epithelial tissue) Dermis (connective tissue) Hypodermis (not part of the skin)

Hypodermis subcutaneous layer (underneath the skin)

Hypodermis contains areolar and adipose tissue

Hypodermis attaches skin to underlying tissues and organs

Hypodermis Conatains pacinian corpuscles ( sensitive to pressure / looks like an onion)

Epidermis Stratified Squamous epithelium 4 different types of cells 5 layers

Types of Cells in Epidermis Keratinocytes Melanocytes Langerhans Merkel

Keratinocytes 90% of epidermal cells

Keratinocytes produce the protein keratin which protects the skin and underlying tissues from heat, microbes, and chemicals

Keratinocytes produce lamellar granules which produce a water repellant sealant

Melanocytes 8 % of epidermal cells

Melanocytes Produces the pigment melanin

Melanocytes Transfers melanin granules to keratinocytes

Melanocytes In keratinocytes the melanin granules acts like an umbrella over the DNA in order to protect it from UV light

Langerhans migrate from red bone marrow to epidermis

Langerhans involved in immune response

Merkel sensitive to touch

Merkel located in stratum basale

Merkel Have contact with the flattened process of a sensory neuron (Merkel disc)

5 layers of Epidermis Stratum Basale Stratum Spinosum Stratum Granulosum Stratum Lucidum Stratum Corneum

Stratum Basale Deepest layer of the epidermis

Stratum Basale Single layer of cuboidal or columnar keratinocytes

Stratum Basale Nuclei large

Stratum Basale Also contains some melanocytes, merkel cells, and langerhans cells

Stratum Spinosum 8 to 10 layers of squamous shaped keratinocytes

Stratum Spinosum Has a large nucleus

Stratum Spinosum Appear spiny underneath microscope

Stratum Spinosum Some langerhans cells and melanocytes

Stratum Granulosum 3 to five layer of squamous keratinocytes

Stratum Granulosum Undergoing apoptosis (cell death)

Stratum Granulosum Nuclei disappearing

Stratum Granulosum Contains protein keratohyalin which converts tonofilaments into keratin

Stratum Granulosum Secretes lamellar granules which fills the spaces between stratum granulousum, stratum lucidum, and stratum corneum

Stratum Lucidum Only in thick skin

Stratum Lucidum 3 to 5 layers of clear, dead, squamous keratinocytes

Stratum Lucidum Contain keratin

Stratum Corneum 25 to 30 layers

Stratum Corneum Dead squamous keratinocytes

Stratum Corneum Contain keratin

Stratum Corneum Sometimes forms callus (the stratum corneum is abnormally thick)

Dermis Two Regions Papillary Region Reticular Region

Papillary Region Contains areolar connective tissue with fine elastic fibers

Papillary Region 20 percent or one fifth of dermis

Papillary Region Contains Meisner corpuscles ( sensitive to touch)

Papillary Region Contains dermal papillae (small,fingerlike projections that indent the epidermis and some contain capillary loops)

Reticular Region Contains dense irregular connective tissue with collagen fibers and course elastic fibers

Reticular Region Contain some adipocytes, hair follicles, nerves, sebaceous glands, and sweat glands

Skin Color Melanin Carotene Hemoglobin

Melanin Number of melanocytes doesn’t vary among people

Melanin Differences in skin color can be attributed to the amount that these melanocytes produce

Melanin Melanocytes most commonly found in the epidermis of the penis, nipples, face and limbs

Melanin Freckles and age spot (accumulations of melanin)

Carotene Yellow-orange pigment Precursor to vitamin A

Carotene Found in stratum corneum, fatty areas of dermis, and hypodermis

Hemoglobin Protein in rbc’s that carries oxygen Found in capillaries in blood

Albinos Contain melanocytes, but are unable to produce melanin Inherited Melanin is absent in hair, eyes, and skin

Vitiligo Irregular white spots Due to loss of melanocytes Antibodies in body attack melanocytes

Types of Skin Thin Skin Thick Skin

Thin Skin Covers all surfaces except palms, fingertips, and soles

Thin Skin Lacks stratum lucidum Thin stratum spinosum and corneum

Thin Skin Lack epidermal ridges (fingerprints)

Thin Skin Fewer sweat glands Fewer sensory receptors

Thin Skin Contains hair follicles, arrector pili muscles, and sebaceous (oil) gland

Thick Skin Located on palms, fingertips, and soles

Thick Skin Stratum Lucidum Thicker stratum spinosum and corneum

Thick Skin Contains epidermal ridges Contains more sweat glands

Thick Skin Lacks hair follicles, sebaceous glands, and arector pili muscles

Accessory Structures Hair Glands Nails

Hair Shaft Superficial portion of hair

Hair Root Penetrates into dermis

Hair Root and Shaft contain three layers Inner medulla(may lack in thin hair), cortex (contains pigment granules), and cuticle

Hair Hair Follicle Surrounds the root of the hair Contains an external root sheath (continuation of epidermis) and internal root sheath (produced by the matrix)

Hair Bulb Contains papilla of hair (areolar connective tissue and blood vessels to nourish hair) Contains matrix (produce new hairs)

Hair Sebaceous glands and arrector pili muscle associated with hairs

Hair Arrector pili muscle responsible for “goose bumps”