5 Flashcards
What is tissue?
Tissue is a group of similar cells that perform a common function.
What are the four primary types of tissue in the body?
The four primary types of tissue are epithelial, connective, muscle, and nervous.
What is epithelial tissue?
Epithelial tissue is composed of tightly packed cells that form a continuous layer, which covers and lines body surfaces and organs.
What are the two main types of epithelial tissue and what are their functions?
The two main types of epithelial tissue are coverings and linings and glandular. Coverings and linings protect, absorb, secrete, and excrete. Glandular epithelium produces and secretes substances.
What are the shapes of epithelial cells and what are their functions?
The shapes of epithelial cells include squamous (thin and flat), cuboidal (cube-shaped), and columnar (tall and column-like). Squamous cells allow for rapid diffusion, cuboidal cells secrete and absorb, and columnar cells secrete mucus and absorb nutrients.
What is connective tissue?
Connective tissue supports, protects, and binds organs. It is the most abundant and diverse type of tissue in the body.
What are the three types of fibers found in connective tissue and what are their functions?
The three types of fibers found in connective tissue are collagen (strong and flexible), elastic (stretchy), and reticular (fine, branching fibers that form a network). They provide strength, elasticity, and support.
What is muscle tissue?
Muscle tissue contracts to produce movement.
What are the three types of muscle tissue and where are they found?
The three types of muscle tissue are skeletal (attached to bones), cardiac (found only in the heart), and smooth (found in the walls of hollow organs).
What is nervous tissue?
Nervous tissue contains cells that transmit and receive electrical impulses, allowing for communication between different parts of the body.
What are the two types of cells found in nervous tissue and what are their functions?
The two types of cells found in nervous tissue are neurons (transmit and receive electrical signals) and neuroglia (support and protect neurons).
What is a tissue membrane?
A tissue membrane is a thin layer of tissue that covers and lines body surfaces and organs.
What are the four types of tissue membranes and where are they found?
The four types of tissue membranes are mucous (lines body cavities that open to the exterior), serous (lines body cavities that do not open to the exterior), cutaneous (covers the body surface), and synovial (lines joint cavities).
What is the difference between endocrine and exocrine glands?
Endocrine glands secrete hormones directly into the bloodstream, while exocrine glands secrete substances into ducts that lead to body surfaces or organs.
What is skeletal muscle?
Skeletal muscle is a type of striated muscle that is attached to bones and responsible for voluntary movement.
What is a muscle fiber?
A muscle fiber is a single, multinucleate cell that makes up skeletal muscle tissue.
What is a myofibril?
A myofibril is a cylindrical structure within a muscle fiber that contains contractile proteins called actin and myosin.
What is a sarcomere?
A sarcomere is the smallest functional unit of a muscle fiber, consisting of overlapping actin and myosin filaments.
What is the sliding filament theory?
The sliding filament theory is the explanation for how muscle contraction occurs. It states that the actin and myosin filaments slide past each other, causing the sarcomere to shorten.
What is the neuromuscular junction?
The neuromuscular junction is the point where a motor neuron meets a skeletal muscle fiber. It is the site of communication between the nervous system and the muscular system.
What is the role of acetylcholine in muscle contraction?
Acetylcholine is a neurotransmitter that is released by motor neurons at the neuromuscular junction. It binds to receptors on the muscle fiber, causing depolarization and muscle contraction.
What is muscle tension?
Muscle tension is the force exerted by a contracting muscle. It can be measured in pounds or newtons.
What is muscle tone?
Muscle tone is the continuous, low-level contraction of skeletal muscle fibers. It helps to maintain posture and stabilize joints.
What is muscle fatigue?
Muscle fatigue is the decline in muscle tension and/or the inability to maintain a given level of muscle tension. It can be caused by factors such as depletion of energy stores or accumulation of waste products in the muscle.
What are the two layers of the skin?
The two layers of the skin are the epidermis and dermis.
What is the epidermis?
The epidermis is the outermost protective shield of the body composed of epithelial cells.
What is the dermis?
The dermis is the underlying layer of the skin, making up the bulk of the skin and composed mostly of dense connective tissue.
What is the subcutaneous tissue?
The subcutaneous tissue, also known as the hypodermis or superficial fascia, is a layer of adipose and areolar connective tissue that lies just deep to the skin. It is not part of the skin but shares some of the skin’s protective functions and anchors the skin to underlying structures.
What is the tissue type composing the epidermis?
The epidermis is a keratinized stratified squamous epithelium.
What are the four distinct cell types found in the epidermis?
The four distinct cell types found in the epidermis are keratinocytes, melanocytes, dendritic cells, and tactile epithelial cells.
What is the chief role of keratinocytes in the epidermis?
The chief role of keratinocytes in the epidermis is to produce keratin, the fibrous protein that helps give the epidermis its protective properties.
What is the role of melanocytes in the epidermis?
Melanocytes in the epidermis synthesize the pigment melanin and transfer it to nearby keratinocytes, forming a pigment shield that protects the nucleus from the damaging effects of ultraviolet (UV) radiation in sunlight.
What are dendritic cells in the epidermis?
Dendritic cells in the epidermis are star-shaped cells that ingest foreign substances and are key activators of our immune system
What are the major layers of the epidermis in thick skin?
The major layers of the epidermis in thick skin, from deep to superficial, are stratum basale, stratum spinosum, stratum granulosum, stratum lucidum, and stratum corneum.
What is the difference between thick and thin skin?
In thick skin, the epidermis consists of five layers, including the stratum lucidum, and covers areas subject to abrasion. In thin skin, the epidermis is thinner and does not have a stratum lucidum, and covers the rest of the body.
What are the functions of bones?
Bones provide support for the body, protect internal organs, assist in movement, store and release minerals and fat, and produce blood cells.
What is ossification?
Ossification is the process by which bone forms. It begins in the embryo and continues until early adulthood.
What are the two types of ossification?
The two types of ossification are intramembranous ossification and endochondral ossification.
What is intramembranous ossification?
Intramembranous ossification is the process by which bone forms directly from mesenchymal cells. It occurs in flat bones such as the skull bones.
What is endochondral ossification?
Endochondral ossification is the process by which bone forms from hyaline cartilage. It occurs in most bones of the body.
What are the two types of bone tissue?
The two types of bone tissue are compact bone and spongy bone.
What is compact bone?
Compact bone is dense and strong bone tissue that forms the outer layer of bones.
What is spongy bone?
Spongy bone is less dense bone tissue that is found in the interior of bones
What are the two main types of bone cells?
The two main types of bone cells are osteoblasts and osteoclasts.
What are osteoblasts?
Osteoblasts are bone-forming cells that secrete the matrix of bone.
What are osteoclasts?
Osteoclasts are bone-resorbing cells that break down bone tissue.
What is bone remodeling?
Bone remodeling is the process by which bone is continuously broken down and rebuilt. It is important for maintaining bone strength and repairing damage.
What is the function of the sarcoplasmic reticulum in a muscle cell?
The sarcoplasmic reticulum stores and releases calcium ions for muscle contraction.
What is a muscle twitch?
A muscle twitch is a single contraction-relaxation cycle in a muscle fiber in response to a single action potential.
What is the difference between a muscle twitch and a tetanic contraction?
A muscle twitch is a brief, isolated contraction, while a tetanic contraction is a sustained contraction resulting from high-frequency stimulation of a muscle fiber.
What is the difference between isotonic and isometric contractions?
Isotonic contractions result in movement of a load, while isometric contractions do not result in movement of a load but instead increase tension in a muscle.
What is muscle tone?
Muscle tone is the state of partial contraction that keeps muscles firm and ready to respond.
What is muscle fatigue?
Muscle fatigue is the decline in muscle tension as a result of previous contractile activity.
What causes muscle soreness after exercise?
Muscle soreness after exercise is caused by microscopic tears in muscle fibers and the resulting inflammation and repair processes.
What is the difference between slow-twitch and fast-twitch muscle fibers?
Slow-twitch muscle fibers contract more slowly and have more endurance, while fast-twitch muscle fibers contract more quickly and are used for more powerful, quick movements.
What is the difference between aerobic and anaerobic respiration in muscle cells?
Aerobic respiration uses oxygen to produce ATP and is more efficient, while anaerobic respiration produces ATP without oxygen and is less efficient but can provide energy more quickly.
What is the role of creatine phosphate in muscle contraction?
Creatine phosphate donates a phosphate group to ADP to quickly produce ATP for muscle contraction during short bursts of activity.
What is the function of the integumentary system?
The integumentary system protects the body from external damage, regulates body temperature, and helps to synthesize vitamin D.
What are the layers of the skin?
The layers of the skin are the epidermis, dermis, and hypodermis (subcutaneous layer).
What is the epidermis?
The epidermis is the outermost layer of the skin, composed primarily of stratified squamous epithelium.
What is the dermis?
The dermis is the layer of skin beneath the epidermis, composed of connective tissue with embedded blood vessels, nerves, and other structures.
What is the hypodermis?
The hypodermis is a layer of connective tissue and adipose (fat) tissue beneath the dermis.
What are the cells found in the epidermis?
The cells found in the epidermis include keratinocytes, melanocytes, and Langerhans cells.
What is the function of keratinocytes?
Keratinocytes produce keratin, a fibrous protein that gives the skin its strength and durability.
What is the function of melanocytes?
Melanocytes produce the pigment melanin, which helps to protect the skin from the harmful effects of ultraviolet (UV) radiation.
What is the function of Langerhans cells?
Langerhans cells are a type of immune cell that helps to protect the skin from infection and other foreign invaders.
What is the structure of the dermis?
The dermis is composed of two layers: the papillary layer, which is made up of loose connective tissue and contains blood vessels and nerve endings, and the reticular layer, which is made up of dense connective tissue and contains collagen and elastic fibers.
What is a sarcomere?
A sarcomere is the functional unit of a muscle fiber, consisting of overlapping thick and thin filaments.
What is the sliding filament model of muscle contraction?
The sliding filament model of muscle contraction states that during contraction, the thin filaments slide past the thick filaments, causing the sarcomere to shorten.
What is the role of calcium ions in muscle contraction?
Calcium ions bind to troponin, causing a conformational change that exposes the active sites on the thin filaments, allowing the myosin heads to bind and initiate muscle contraction.
What is the role of ATP in muscle contraction?
ATP is required for myosin heads to detach from actin and reset for the next contraction cycle.
What is the role of the motor neuron in muscle contraction?
The motor neuron releases acetylcholine at the neuromuscular junction, which stimulates the muscle fiber to contract.
What is the role of the neuromuscular junction in muscle contraction?
The neuromuscular junction is the synapse between a motor neuron and a muscle fiber, where acetylcholine is released to stimulate muscle contraction.
What is the role of the sarcoplasmic reticulum in muscle contraction?
The sarcoplasmic reticulum stores and releases calcium ions, which are required for muscle contraction.
What is the difference between isometric and isotonic contractions?
Isometric contractions involve muscle tension without a change in muscle length, while isotonic contractions involve a change in muscle length without a change in muscle tension.
What is muscle fatigue?
Muscle fatigue is the decline in muscle performance due to prolonged or intense muscle activity.
What is the difference between slow-twitch and fast-twitch muscle fibers?
Slow-twitch muscle fibers contract slowly and are fatigue-resistant, while fast-twitch muscle fibers contract quickly and are more prone to fatigue.
Stratum Basale (Basal Layer)
Deepest epidermal layer
Also called the stratum germinativum
Attached to underlying dermis along a wavy borderline resembling corrugated cardboard
Consists of a single row of stem cells that represent the youngest keratinocytes
How does stratum basale function?
Rapid division of these cells leads to many mitotic nuclei seen in this layer
Daughter cells specialize into mature keratinocytes or continue producing new keratinocytes
Contains 10-25% of melanocytes with branching processes extending among surrounding cells
Stratum Spinosum (Prickly Layer)
Several cell layers thick
Contains keratinocytes with spinelike extensions that look like tiny spiked iron balls under a microscope
These spines are artifacts created during tissue preparation due to the cells shrinking while holding tight at their many desmosomes
Cells contain thick bundles of intermediate filaments that resist tension in the cell and are anchored to the desmosomes
Scattered among the keratinocytes are dendritic cells, which are most abundant in this layer
Stratum Granulosum (Granular Layer)
Thin layer consisting of one to five cell layers
Keratinocyte appearance changes drastically, and the process of keratinization begins
Cells flatten, their nuclei and organelles begin to disintegrate, and they accumulate two types of granules
How does the stratum granulosum function?
Keratohyaline granules help to form keratin in the upper layers
Lamellar granules contain a water-resistant glycolipid that is secreted into the extracellular space
Together with tight junctions, the glycolipid plays a major part in slowing water loss across the epidermis
Proteins within the keratinocytes and lipids deposited outside them make these cells tough and water-resistant
Stratum Lucidum (Clear Layer)
Found only in thick skin
Visible through a light microscope as a thin translucent band just above the stratum granulosum
Consists of a few rows of flat, dead keratinocytes
Electron microscopy reveals that its cells are identical to those at the bottom of the next layer, the stratum corneum
Stratum Corneum (Horny Layer)
Outermost epidermal layer
Broad zone 20 to 30 cell layers thick that accounts for up to three-quarters of the epidermal thickness
An abrupt transition occurs between the nucleated cells of the stratum granulosum and the flattened, anucleate cells of the stratum corneum
Keratin consists of the pre-keratin intermediate filaments embedded in a “glue” from the keratohyaline granules
How does the Stratum Corneum function?
Keratin and proteins that accumulate just inside the plasma membrane of cells in this stratum protect the skin against abrasion and penetration
The glycolipid between its cells helps keep this layer nearly waterproof
Even though it is made up of dead cells, it still performs many functions
Cells of the stratum corneum are shed regularly, accounting for dandruff and flakes of dry skin
What is the dermis made up of?
The dermis is made up of strong, flexible connective tissue.
What are the cells typical of the dermis?
The cells typical of the dermis are fibroblasts, macrophages, mast cells, and white blood cells.
What is the matrix of the dermis embedded with?
The matrix of the dermis is embedded with fibers.
What are the two layers of the dermis?
The two layers of the dermis are the papillary dermis and the reticular dermis.
What type of tissue is the papillary dermis made of?
The papillary dermis is made of areolar connective tissue.
What are dermal papillae?
Dermal papillae are peglike projections from the surface of the papillary dermis that indent the overlying epidermis.
What is the function of the looseness of the connective tissue in the papillary dermis?
The looseness of the connective tissue in the papillary dermis allows phagocytes and other defensive cells to wander freely as they patrol the area for bacteria that have penetrated the skin.
What are tactile corpuscles?
Tactile corpuscles are touch receptors called Meissner’s corpuscles.
What are epidermal ridges?
Epidermal ridges are formed by the dermal ridges that lie atop the papillary dermis in thick skin, such as the palms of the hands and soles of the feet.
What are friction ridges?
Friction ridges are the skin ridges formed by epidermal ridges that enhance our ability to grip certain kinds of surfaces.
What are cleavage lines?
Cleavage lines are separations between underlying collagen fiber bundles in the reticular dermis.
What is the function of cleavage lines for surgeons?
Cleavage lines are important to surgeons because when an incision is made parallel to these lines, the skin gapes less and heals more readily.
What is the reticular dermis made of?
The reticular dermis is made of coarse, dense irregular connective tissue.
What is the function of the collagen fibers of the dermis?
The collagen fibers of the dermis give skin strength, extensibility, and elasticity.
What is osmosis?
Osmosis is the diffusion of water molecules across a selectively permeable membrane from an area of high water concentration to an area of low water concentration.
What is tonicity?
Tonicity refers to the ability of a solution to cause a cell to gain or lose water.
What is a hypertonic solution?
A hypertonic solution has a higher concentration of solutes (such as salt or sugar) compared to the concentration of solutes inside a cell. This causes water to move out of the cell, leading to cell shrinkage.
What is a hypotonic solution?
A hypotonic solution has a lower concentration of solutes compared to the concentration of solutes inside a cell. This causes water to move into the cell, leading to cell swelling and potential lysis (bursting).
What is an isotonic solution?
An isotonic solution has the same concentration of solutes as the concentration of solutes inside a cell. This causes no net movement of water, and the cell remains in its normal shape and size.
What is facilitated diffusion?
Facilitated diffusion is a type of passive transport where a substance (such as glucose or amino acids) is transported across a cell membrane from an area of high concentration to an area of low concentration with the help of a carrier protein. No energy input is required.
What is active transport?
Active transport is a type of membrane transport that requires energy in the form of ATP to move substances against their concentration gradient (from low to high concentration). This is carried out by specialized proteins called pumps.
What is endocytosis?
Endocytosis is a process by which cells take in large molecules or particles by forming vesicles from the plasma membrane. There are two main types of endocytosis: phagocytosis, where solid particles are engulfed, and pinocytosis, where fluids and dissolved substances are taken in.
What is exocytosis?
Exocytosis is the process by which cells release large molecules or particles by fusing vesicles with the plasma membrane, expelling the contents outside the cell.
What determines skin color?
Melanin, carotene, and hemoglobin. Melanin is a polymer made of an amino acid called tyrosine. Melanin synthesis depends on an enzyme in melanocytes called tyrosinase. Carotene is a yellow to orange pigment found in certain plant products. Hemoglobin is the oxygenated pigment in the red blood cells circulating through the dermal capillaries.
What causes skin to darken visibly?
Keratinocytes secrete chemicals that stimulate melanocytes. Prolonged sun exposure causes a substantial melanin buildup, which helps protect the DNA of skin cells from UV radiation by absorbing the rays and dissipating the energy as heat.
What is blueness and what does it indicate?
Blueness (cyanosis), which can indicate respiratory or cardiovascular problems.
What is pallor and what does it indicate?
Pallor, which can indicate emotional stress, low blood pressure, or anemia.
What is redness and what does it indicate?
Redness (erythema), which can indicate embarrassment, fever, inflammation, or allergy.
What is yellowness and what does it indicate?
Yellowness (jaundice), which can indicate liver dysfunction.
What are bruises and what do they indicate?
Bruises (ecchymoses or hematomas), which can indicate damage to blood vessels.
What are dark areas and what do they indicate?
Dark areas in the axillae and around the neck may be a sign of insulin resistance and elevated blood glucose.
What is melanin?
Melanin is a polymer made of an amino acid called tyrosine. Its two forms range in color from reddish yellow to brownish black.
What determines skin color?
Differences in skin coloring reflect the kind and amount of melanin made and retained.
What happens when we expose our skin to sunlight?
Keratinocytes secrete chemicals that stimulate melanocytes. Prolonged sun exposure causes a substantial melanin buildup, which helps protect the DNA of skin cells from UV radiation by absorbing the rays and dissipating the energy as heat.
What is carotene and where is it found?
Carotene is a yellow to orange pigment found in certain plant products such as carrots. It tends to accumulate in the stratum corneum and in the fat of the subcutaneous tissue.
What is the function of hemoglobin in skin color?
The pinkish hue of fair skin reflects the crimson color of the oxygenated pigment hemoglobin in the red blood cells circulating through the dermal capillaries.
Hair
Flexible strands produced by hair follicles and consist largely of dead, keratinized cells.
Hair Follicles
Tubular invaginations of the epidermis from which the hairs grow.
Root of Hair
The part of the hair that is embedded in the skin.
Shaft of Hair
The part of the hair that projects above the skin’s surface.
Medulla
The central core of a hair consisting of large cells and air spaces.
Cortex
A bulky layer surrounding the medulla of a hair.
Cuticle
The outermost layer of a hair formed from a single layer of cells overlapping one another like shingles on a roof.
Hair Pigment
Made by melanocytes at the base of the hair follicle and transferred to the cortical cells, giving hair color from blond to brown to black.
Hair Follicle Receptor
A knot of sensory nerve endings that wraps around each hair bulb and is stimulated when the hair is bent, acting as sensitive touch receptors.
Hair Papilla
A dermal papilla that protrudes into the hair bulb and contains a knot of capillaries that supplies nutrients to the growing hair and signals it to grow.
Function of Arrector Pili Muscles
A small bundle of smooth muscle cells that extends from the superficial dermis to the side of the hair follicle and contracts in response to cold or fear, making the hair “stand up” and producing goosebumps.
Regions of a Hair
The root, the part embedded in the skin, and the shaft, the part that projects above the skin’s surface.
Hair Color
Different concentrations of melanin produce hair color from blond to brown to black. Red hair is colored by a related pigment called pheomelanin.
Distribution of Hair
Millions of hairs are distributed over our entire skin surface except our palms, soles, lips, nipples, and parts of the external genitalia.
Growth and Replacement of Hair
Hair grows and is replaced throughout a person’s life span, with growth and replacement rates varying depending on the location of the hair.
Changing Nature of Hair
As melanin production decreases and air bubbles replace melanin in the hair shaft, hair turns gray or white.
Parts of a Hair Follicle
The hair bulb, hair papilla, epithelial root sheath, glassy membrane, and peripheral connective tissue sheath.
Function of Hair
Hair helps to sense insects on the skin before they bite or sting us and guards the head against physical trauma, heat loss, and sunlight. Eyelashes shield the eyes, and nose hairs filter large particles like lint and insects from the air we inhale.
Sebaceous (oil) glands
Holocrine glands that discharge an oily lipid secretion into hair follicles or onto the skin surface.
Sweat glands
Two types: Eccrine glands produce a clear, watery sweat that cools the body when it evaporates, while apocrine glands produce a thicker, milky sweat that contains fatty acids and proteins, and begins to function at puberty.
Ceruminous glands
Modified sweat glands that discharge a waxy secretion into the external ear canal.
Mammary glands
Modified sweat glands that produce milk.
Basal cell carcinoma
The least malignant and most common type of skin cancer. It arises from the stratum basale and eventually invades the dermis.
Nails
Scale-like modifications of the epidermis that form a clear protective covering on the dorsal surface of the distal part of a finger or toe.
Nail plate
The visible attached portion of the nail body that ends in the free edge.
Nail bed
A bed of epidermis that supports the nail plate.
Nail matrix
The thickened proximal portion of the nail bed that is responsible for nail growth.
Lunule
A white crescent-shaped region that lies over the thick nail matrix and appears on the proximal end of the nail body.
Cuticle
A thickened region beneath the free edge of the nail plate that projects onto the nail body and overlaps the proximal nail fold.
Hyponychium
The thickened region beneath the free edge of the nail plate that secures the free edge of the nail plate at the tip of the finger or toe.
Koilonychia
An outward concavity of the nail (spoon nail) that may signal an iron deficiency.
Beau’s lines
Horizontal lines across the nails that can be a sign of severe illness that affects the whole body such as uncontrolled diabetes, a heart attack, or cancer chemotherapy.
Hard keratin
The type of keratin found in nails and hairs, which is harder and more durable than the soft keratin found in the epidermis.
Clinical significance of nail appearance
Changes in nail appearance can help diagnose certain conditions, such as yellow-tinged nails indicating a respiratory or thyroid gland disorder or thickened yellow nails indicating a fungal infection.
Cutaneous glands
Exocrine glands that release their secretions to the skin surface via ducts
Sebaceous glands
Glands that produce sebum, an oily substance that lubricates the hair and skin and inhibits bacterial growth
Sweat glands
Glands that produce sweat, which helps regulate body temperature by evaporative cooling
Eccrine glands
Sweat glands that are widely distributed over the body surface and primarily function in thermoregulation
Apocrine glands
Sweat glands that are mainly confined to the axillary and genital areas and are responsible for body odor when acted upon by bacteria
Mammary glands
Modified sweat glands that produce milk
Ceruminous glands
Modified sweat glands located in the ear canal that produce earwax (cerumen) to help protect the ear drum
Acne
A common skin disorder caused by inflammation of the sebaceous glands, leading to the formation of pimples and other lesions on the skin
What are sweat glands also known as?
Sweat glands are also known as sudoriferous glands.
How many sweat glands can a person have?
Up to 3 million per person.
What is the function of sweating?
The function of sweating is to control body temperature.
What are the two types of sweat glands?
Eccrine and apocrine glands.
Which is more abundant, eccrine or apocrine glands?
Eccrine glands.
What is the composition of sweat?
99% water, salts (mostly sodium chloride), traces of metabolic wastes (urea, uric acid, and ammonia), and a microbe-killing peptide called dermcidin.
What is the pH of sweat?
Between 4 and 6.
What is the major role of sweating?
To prevent the body from overheating.
What is the function of apocrine glands?
Their precise function is not yet known.
What is the secretion of apocrine glands composed of?
Fatty substances and proteins.
What causes body odor?
Bacteria on the skin decomposing the organic molecules in apocrine secretion.
What are the two important types of modified apocrine glands?
Ceruminous glands and mammary glands.
What is the function of ceruminous glands?
To form a sticky, bitter substance called cerumen, or earwax, that is thought to deter insects and block entry of foreign material.
What is the function of mammary glands?
To secrete milk.
What are sebaceous glands also known as?
Sebaceous glands are also known as oil glands.
Where are sebaceous glands found?
All over the body except in the thick skin of the palms and soles.
What is sebum?
An oily substance.
What is the function of sebum?
To soften and lubricate the hair and skin, prevent water loss from the skin, and inhibit the growth of certain bacteria.
What is the function of skeletal muscle?
To move bones and other structures by contracting and relaxing
What is the structure of skeletal muscle?
Muscle fibers, which are composed of myofibrils, which are composed of sarcomeres, which contain thick and thin filaments made of contractile proteins.
What is a motor unit?
A motor neuron and all the muscle fibers it innervates.
What is the neuromuscular junction?
The point where a motor neuron meets a muscle fiber, allowing the motor neuron to transmit a signal to the muscle fiber to contract.
What is the sliding filament theory of muscle contraction?
The theory that muscle contraction occurs when thin filaments slide past thick filaments, causing sarcomeres to shorten and the muscle fiber as a whole to contract.
What is the role of calcium in muscle contraction?
Calcium binds to troponin, causing it to change shape and move tropomyosin, which then allows the myosin heads to bind to actin and begin the power stroke that pulls the thin filament toward the center of the sarcomere.
What is a twitch contraction?
A brief contraction of a muscle fiber caused by a single action potential in its motor neuron.
What is tetanus in muscle contraction?
A sustained contraction of a muscle fiber caused by repeated stimulation of its motor neuron, so that the fiber does not have time to relax completely between stimuli.
Function of skin
Protection
Body temperature regulation
Cutaneous sensation
Metabolic functions
Blood reservoir
Excretion
List some chemical barriers
Skin secretions
Melanin
Dermcidin in sweat
Bactericidal substances in sebum
Natural antibiotics called defensins
Protective peptides called cathelicidins
List some physical barriers
Structure of stratum corneum
Glycolipids surrounding dead flat cells
Water-resistant glycolipids
Diffusion of water and water-soluble substances
Lipid-soluble substances
Oleoresins of certain plants
Organic solvents
Salts of heavy metals
Selected drugs
Penetration enhancer
What causes homeostatic imbalance
Organic solvents and heavy metals
Passage of organic solvents through the skin into the blood
Absorption of lead
Anemia and neurological defects
Biological barriers
Dendritic cells of the epidermis
Macrophages in the dermis
Body Temperature Regulation Measures
Homeostatic limits
Heat generated by internal reactions
Loss of heat to the air and to cooler objects in the environment
Dermal blood vessels to dilate
Vigorous secretory activity
Dermal blood vessels constrict
