The Integumentary System Chapter 6

General Information About the Integumentary System Covers approx. 2 square meters (20 sq. ft.) Covers approx. 2 square meters (20 sq. ft.) Accounts for 15% of total body weight Accounts for 15% of total body weight Major organ is the skin, but also includes hair, glands, receptors, and blood vessels Major organ is the skin, but also includes hair, glands, receptors, and blood vessels

Functions Protection – physical barrier against loss of body fluids, physical injury, UV light, and pathogens Protection – physical barrier against loss of body fluids, physical injury, UV light, and pathogens Regulates body temperature – sweat, blood circulation Regulates body temperature – sweat, blood circulation Communication – sensory receptors relay info. regarding heat, cold, touch and pain to brain Communication – sensory receptors relay info. regarding heat, cold, touch and pain to brain

Functions cont’d Excretion of waste – sweat glands release small amounts of urea Excretion of waste – sweat glands release small amounts of urea Vitamin D production – when exposed to UV light, aids in absorption of calcium Vitamin D production – when exposed to UV light, aids in absorption of calcium

The Skin Largest organ of integumentary system Largest organ of integumentary system Thin, superficial layer of stratified squamous epithelial tissue called the epidermis Thin, superficial layer of stratified squamous epithelial tissue called the epidermis Thick, deeper layer of connective tissue called the dermis Thick, deeper layer of connective tissue called the dermis

The Skin cont’d Between skin and muscle is the hypodermis, also called the superficial fascia or subcutaneous layer Between skin and muscle is the hypodermis, also called the superficial fascia or subcutaneous layer

The Epidermis Dynamic sheet of cells that forms a waterproof, protective wrap over the body’s surface Dynamic sheet of cells that forms a waterproof, protective wrap over the body’s surface Millions of cells in the epidermis are worn away by the activities of everyday life Millions of cells in the epidermis are worn away by the activities of everyday life Made of stratified squamous epithelium Made of stratified squamous epithelium

The Epidermis cont’d Deepest layer contains living, rapidly dividing columnar cells that push older cells toward the surface Deepest layer contains living, rapidly dividing columnar cells that push older cells toward the surface Older cells flatten and die as they near the surface; cell contents are replaced by a protein called keratin Older cells flatten and die as they near the surface; cell contents are replaced by a protein called keratin

Layers of Epidermis Stratum corneum Stratum lucidum Stratum granulosum Stratum spinosum Stratum basale

Stratum Basale Deepest layer of epidermis Deepest layer of epidermis Columnar / cuboidal cells form bottom layer, closest to vascular dermis Columnar / cuboidal cells form bottom layer, closest to vascular dermis Require nutrients for rapid cell division Require nutrients for rapid cell division Push previously formed cells toward the surface Push previously formed cells toward the surface

Stratum spinosum Multiple-layered arrangement of cuboidal cells Multiple-layered arrangement of cuboidal cells Contain molecular bridges that connect them to adjacent cells, gives them a “prickly” appearance Contain molecular bridges that connect them to adjacent cells, gives them a “prickly” appearance

Stratum spinosum cont’d Nuclei are often darkened, a condition called pyknosis, which is an early sign of cell death Nuclei are often darkened, a condition called pyknosis, which is an early sign of cell death Cells begin to die because they’re cut off from supply of nutrients and oxygen Cells begin to die because they’re cut off from supply of nutrients and oxygen

Stratum granulosum 3 to 5 rows of partially flattened cells 3 to 5 rows of partially flattened cells Cells contain granules of proteins that stain dark and are intermediate to the formation of keratin Cells contain granules of proteins that stain dark and are intermediate to the formation of keratin

Stratum lucidum Present only in the thick skin of the palms and soles Present only in the thick skin of the palms and soles 3 to 4 rows of flattened, dead cells that are mostly transparent 3 to 4 rows of flattened, dead cells that are mostly transparent

Stratum corneum Most superficial layer Most superficial layer 20 – 50 rows of flattened, dead cells 20 – 50 rows of flattened, dead cells Are “sloughed off” as a result of normal wear and tear Are “sloughed off” as a result of normal wear and tear

Stratum Corneum cont’d Entire journey from stratum basale to surface takes between 3 and 4 weeks Entire journey from stratum basale to surface takes between 3 and 4 weeks By this time, cells are nothing but “ghosts” having their contents completely replaced by keratin By this time, cells are nothing but “ghosts” having their contents completely replaced by keratin

Layers of Epidermis Stratum corneum Stratum lucidum Stratum granulosum Stratum spinosum Stratum basale

Skin Color Melanocytes produce the primary skin pigment, melanin Melanocytes produce the primary skin pigment, melanin Located between cells in the stratum basale Located between cells in the stratum basale

Skin Color cont’d Melanin is a dark brown pigment, more melanin result in darker skin colors Melanin is a dark brown pigment, more melanin result in darker skin colors Skin color is not determined by number of melanocytes, but by how much melanin they produce (genetic and environmental factors) Skin color is not determined by number of melanocytes, but by how much melanin they produce (genetic and environmental factors)

Skin Color cont’d Exposing melanocytes to UV radiation results stimulates them to produce more melanin, a process called tanning Exposing melanocytes to UV radiation results stimulates them to produce more melanin, a process called tanning Melanin has the ability to absorb UV light, protecting cells’ DNA Melanin has the ability to absorb UV light, protecting cells’ DNA

Skin Color cont’d Skin color can also receive contributions from carotene, a yellowish pigment (most prominent in Asians, but also present in caucasians) Skin color can also receive contributions from carotene, a yellowish pigment (most prominent in Asians, but also present in caucasians)

The Dermis Dense mat of various connective tissues Rich with blood vessels Consistencey of a firm wet sponge

The Dermis Papillary region – contains several papillae – form friction ridges Reticular region contains accessory organs

Accessory Organs Hair follicles, finger and toe nails, sebaceous glands, and sweat glands are all referred to as epidermal derivatives because they all grow from cells migrating to the dermis from the epidermis during development Hair follicles, finger and toe nails, sebaceous glands, and sweat glands are all referred to as epidermal derivatives because they all grow from cells migrating to the dermis from the epidermis during development Blood vessels and nerve receptors grow in from other areas Blood vessels and nerve receptors grow in from other areas

Hair Protects skin from injury that may be caused by sunlight or foreign particles Protects skin from injury that may be caused by sunlight or foreign particles Grown from a downward growth of the epidermis into the dermis called a follicle Grown from a downward growth of the epidermis into the dermis called a follicle Portion surrounded by follicle called the root, portion above surface is the shaft Portion surrounded by follicle called the root, portion above surface is the shaft

Hair Hair follicle and root consist of mostly living cells, nourished from a cluster of blood vessels in the base or bulb Hair follicle and root consist of mostly living cells, nourished from a cluster of blood vessels in the base or bulb Growth of hair is similar to replacement of epidermis; cells are pushed to surface Growth of hair is similar to replacement of epidermis; cells are pushed to surface Hair is made mostly of keratinized cells Hair is made mostly of keratinized cells

Hair Hair grows at a rate of 1mm every 3 days Hair grows at a rate of 1mm every 3 days Cutting or shaving it have no effect on rate of growth Cutting or shaving it have no effect on rate of growth Body regions differ in hair growth rate Body regions differ in hair growth rate Approx. 100 scalp hairs are lost daily Approx. 100 scalp hairs are lost daily Hair color determined by amt. of melanin present (blonde, brown, or black); white by decrease in production of melanin and air in shaft Hair color determined by amt. of melanin present (blonde, brown, or black); white by decrease in production of melanin and air in shaft

Sebaceous Glands Also known as oil glands; associated with hair follicles, connected to follicle by a duct Also known as oil glands; associated with hair follicles, connected to follicle by a duct Produce an oily secretion called sebum (consists of water, fats, cholesterol, protein, and salt) Produce an oily secretion called sebum (consists of water, fats, cholesterol, protein, and salt) Sebum keeps hair and skin soft and pliable, also increases water-resistance Sebum keeps hair and skin soft and pliable, also increases water-resistance Production of sebum is accelerated by sex hormones Production of sebum is accelerated by sex hormones

Sebaceous Glands May become clogged by excess sebum, dead cells, or environmental debris; forms blackheads May become clogged by excess sebum, dead cells, or environmental debris; forms blackheads If bacteria become established, forms a pimple or boil If bacteria become established, forms a pimple or boil Sebaceous glands are distributed evenly over entire body except on palms and soles Sebaceous glands are distributed evenly over entire body except on palms and soles

Sebaceous Gland (Yellow)

Sweat Glands Also known as sudoriferous glands Also known as sudoriferous glands Come in two varieties, eccrine and apocrine Come in two varieties, eccrine and apocrine Eccrine – present entire life, secrete a watery sweat, function primarily in cooling Eccrine – present entire life, secrete a watery sweat, function primarily in cooling Eccrine glands are distributed throughout the body Eccrine glands are distributed throughout the body

Sweat Gland

Apocrine Glands Apocrine – become active during puberty, secrete a thick sweat, highest concentration located in armpits and groin Apocrine – become active during puberty, secrete a thick sweat, highest concentration located in armpits and groin Proteins in apocrine sweat promote growth of bacteria normally found on skin; bacteria produce odoriferous materials Proteins in apocrine sweat promote growth of bacteria normally found on skin; bacteria produce odoriferous materials Active primarily in times of emotional stress Active primarily in times of emotional stress

Nails Formed from compressed outer layer of epidermis; mostly keratin Formed from compressed outer layer of epidermis; mostly keratin Protect ends of fingers and toes, function in very fine gripping Protect ends of fingers and toes, function in very fine gripping Visible surface of nail is the nail body, covered by flap of stratum corneum, the cuticle Visible surface of nail is the nail body, covered by flap of stratum corneum, the cuticle

Deep to cuticle is nail root, active stratum basale known as nail matrix Deep to cuticle is nail root, active stratum basale known as nail matrix Small, crescent-shaped portion of matrix is visible, called the lunula Small, crescent-shaped portion of matrix is visible, called the lunula

Receptors Usually consist of the distal ends of nerve cells that are wrapped in connective tissue Usually consist of the distal ends of nerve cells that are wrapped in connective tissue Carry impulses toward the brain, millions found in the skin Carry impulses toward the brain, millions found in the skin Interpreted by the brain as heat, pressure, fine touch, and pain Interpreted by the brain as heat, pressure, fine touch, and pain Give important information necessary for maintaining homeostasis Give important information necessary for maintaining homeostasis

Hypodermis Connects skin to muscles beneath Connects skin to muscles beneath Contains loose connective tissue, adipose tissue, and dense connective tissue Contains loose connective tissue, adipose tissue, and dense connective tissue Insulates deep tissues from extremes of heat and cold, also provides shock absorbing cushion and energy storage Insulates deep tissues from extremes of heat and cold, also provides shock absorbing cushion and energy storage

Temperature Regulation Blood vessels in the dermis dilate (enlarge) or constrict (shrink) to release more or less heat to the environment Blood vessels in the dermis dilate (enlarge) or constrict (shrink) to release more or less heat to the environment Evaporation of sweat is an important factor in cooling Evaporation of sweat is an important factor in cooling Goosebumps and shivering warm up the body Goosebumps and shivering warm up the body