Integumentary System KAYLEE AND JAZZY

Key Terms  Apocrine Sweat Glands: Glands that open into hair follicles  Arrector Pili: a bundle of smooth muscle cells attached to each hair follicle  Eponychium: the cuticle of the fingernail  Hair Shaft: Upper layer of dermis  Hypodermis: the subcutaneous layer  Keratin: tough, water repellant protein in epidermis  Melanocytes: Cells that produce a dark pigment called melanin  Papillary layer: the visible portion of the hair  Stratum Basale: mitotic skin layer of the epidermis  Stratum corneum: the outermost layer of the skin

What is it?  It provides a barrier against hazardous materials and pathogens  The skin and the glands, hair, nails, and other structures make up the system  Since the skin is on the outside of the body, this system is exposed to abuse in the form of bumps, cuts, scrapes, toxic chemicals, pollutants, wind, and sun.  The skin quickly repairs itself and continues to perform many functions

Structure of the Skin  Often called the cutaneous membrane  Consists of two distinct layers of tissues  The outer layer is called the epidermis  The inner layer is called the dermis  These are anchored to the underlying third layer called the subcutaneous tissue

Epidermis  The outer layer of the skin  No blood vessels  Cells receive nutrients from vessels in the underlying tissue  Cells on the bottom actively grow and divide from receiving adequate nutrients  As cells are pushed upward they receive less nutrients  By the time cells reach the top they are dead from lack of nutrients

Epidermis cont.  Stratum basale is the bottom layer, it is closest to the blood supply  Stratum spinosum is the next layer, it consists of several layers of cells  Stratum granulosum is a thin region that consists of 2 or 3 layers of flattened cells  Stratum lucidum consists of a few layers of flattened, anucleate cells. This region only appears in thick skin  Stratum corneum is the surface region, it consists of layers of flattened, dead, completely keratinized cells

Dermis  Dense connective tissue that is deeper and thicker than the epidermis  Hair, nails, and certain glands are embedded in the dermis  Contains both collagenous and elastic fibers to give it strength and elasticity  If the skin is overstretched it could damage the dermis and leave whit scars called striae or “stretch marks”  Dermis is divided into 2 distinct layers called the papillary layer and the reticular layer  Papillary layer is the basis of finger prints and foot prints  Reticular layer is the deeper layer of the dermis that provides strength to the skin

Skin Color  Skin color is due to factors some genetic, some physiologic, and some environmental  Basic skin color is due to the dark pigment melanin produced by the melanocytes  Everyone has about the same number of melanocytes  The activity of melanocytes is genetically controlled  A larger number of melanin granules results in darker skin, a smaller amount of melanin granules results in lighter skin

Skin color cont.  Many genes are responsible for skin color  A single mutation can result in the inability to produce melanin which results in a condition called albinism  Albinism is when an individual have very light skin, white hair, and unpigmented irises in the eyes

Hair and Hair Follicles  Hair is found on almost all body surfaces  Hair is not found on the palms of the hands, soles of the feet, lips, nipples, certain external genitalia, and distal segments of the fingers and toes  All hair consists of a shaft and a root that are composed of dead cells  The shaft of a hair is the portion that extends beyond the epidermis  The shaft contains no nerves, therefore it can be cut with no feeling of pain

Hair and Hair follicles cont.  The root is the portion of hair that is below the surface of the skin  The shaft and root both make up the hair, which is produced by a hair follicle  The central core of the hair is the medulla  The root of a hair is enclosed in a tubular hair follicle

Nails  Thin plates of dead stratum corneum that contain a very hard type of keratin and cover the dorsal surfaces of the distal ends of the fingers and toes  Each nail has a free edge, nail body, and a nail root  The cuticle is a fold of stratum corneum that grows onto a portion of the nail body  Stratum basale grows under the nail body to form a nail bed  The nail matrix is responsible for nail growth  Nails appear pink because of the rich supply blood vessels in the underlying dermis

Glands: The two major glands associated with the skin are the sebaceous glands and the sweat glands  Sebaceous glands  generally associated with hair follicles  found in all areas of body with hair  Sebum- an oily secretion on the surface of the skin  Sebum keeps hair and skin soft and pliable  Sweat glands  Widely distributed around the body except for lips, nipples, and parts of external genitalia  There are more sweat glands in the palms and soles  An individual as about 2.5 mil. sweat glands

Recall 1. Cells that produce a dark pigment 2. Outermost layer of the skin 3. Actively mitotic layer of the epidermis 4. Subcutaneous layer 5. Visible portion of hair 6. Cuticle of fingernail 7. Glands that open into hair follicles 8. Muscle attatched to hair follicles 9. Tough, water repellant protein in epidermis 10. Upper layer of epidermis A. Apocrine sweat glands B. Arrector pili C. Eponychium D. Hair Shaft E. Hypodermis F. Keratin G. Melanocytes H. Papillary layer I. Stratum basale J. Stratum corneum

Answers 1. Cells that produce a dark pigmentA. Melanocytes 2. Outermost layer of the skinB. Stratum Corneum 3. Actively mitotic layer of the epidermisC. Stratum Basale 4. Subcutaneous layerD. Hypodermis 5. Visible portion of hairE. Papillary layer 6. Cuticle of fingernail F. Eponychium 7. Glands that open into hair folliclesG. Apocrine sweat glands 8. Muscle attatched to hair folliclesH. Arrector pili 9. Tough, water repellant protein in epidermisI. Keratin 10. Upper layer of epidermisJ. Hair shaft