Functions: support & shape to body, protection of internal organs, movement in union with muscles, storage of minerals (calcium,phosphorus) & lipids, blood cell production, 20% of the body weight, bones, cartilage, tendons, ligaments
206 Bones: 1. Axial skeleton: (80 bones) in skull, vertebrae, ribs, sternum, hyoid bone (Ushaped bone in the neck that supports tongue) 2. Appendicular Skeleton: (126 bones)upper & lower extremities plus two girdles (pectoral and pelvic)
Types of Bones: Long bones are longer than they are wide; shaft & 2 ends (bones of arms &
legs, except wrist, ankle & patella), Short bones are roughly cube-shaped (ankle & wrist
bones), Sesamoid bones are short bones within tendons (patella), Flat bones are thin, flat
& often curved (sternum, scapulae, ribs & most skull bones), Irregular bones are odd
shapes and don't fit into other classes (hip bones & vertebrae)
Vertebrae: aka backbone or spine, 33 bones, Cervical (7)- transverse foramina, bifid
spinous processes vertebral prominens (Atlas- 1st; supports head Axis- 2nd; pivots to turn
head), Thoracic (12)- long spinous processes, rib facets, Lumbar (5)- large bodies thick,
short spinous processes, Sacrum (5 fused), Coccyx (4 fused)
Synovial Joints: Ball & Socket - allows for complete range of motion, Pivot – one bone
pivots in the arch of another (Axis/Atlas, and proximal radioulnar joint), Saddle – two
directional movement between thumb and trapezium carpal, Hinge – like door hinge –
bending & extending (elbow, knee, finger joints), Ellipsoid (Condyloid) – side to side and back & forth (radius end into carpal bones),
Plane or Gliding – least moveable – side to side only (intercarpal & intertarsal joints,
between vertebrae)
Cartilage: mostly water, no blood vessels or nerves, tough and resilient, new cartilage
forms from chondroblasts, heal poorly
Growth of Cartilage: 1. Appositional – cells in the perichondrium secrete matrix against
the external face of existing cartilage 2. Interstitial – lacunae-bound chondrocytes inside the cartilage divide and secrete new
matrix, expanding the cartilage from within
Types of Cartilage: 1. Hyaline Cartilages - fine collagen fiber matrix- most abundant type- found in articular (movable joint)
cartilages, costal cartilages (connect ribs to sternum), respiratory cartilages (in larynx & upper respiratory passageways) & nasal
cartilages 2. Elastic Cartilages - similar to hyaline cartilage, more elastic fibers (very flexible) – found in external ear & epiglottis
(larynx covering) 3. Fibrocartilage - rows of chondrocytes with thick collagen fibers; highly compressible with great tensile
strength- found in menisci of knee, intervertebral discs & pubic symphysis.
Cellular Structure of a Long Bone: 1. Compact bone - The hard outer layer of bones is composed of compact bone tissue, so-called due to its minimal gaps and spaces. This tissue
gives bones their smooth, white, and solid appearance, and accounts for 80% of the total bone mass of an adult skeleton. Com pact bone may also be referred to as dense bone or
cortical bone. 2. Spongy bone - Filling the interior of the organ is the spongy bone tissue which is composed of a network of rod- and plate-like elements that make the overall organ lighter and allowing room for blood vessels and marrow. Spongy bone accounts for the remaining 20% of total bone mass,
but has nearly ten times the surface area of compact bone.
Types of Bone Cells: 1. Osteoblasts – bone forming cells synthesize and secrete unmineralized ground substance and are found in areas of high metabolism within the bone 2. Osteocytes – mature bone cells made from osteoblasts that have made bone tissue around themselves. These cells maintain
healthy bone tissue by secreting enzymes and controlling the bone mineral content; they also control the calcium release from the bone tissue to the blood 3. Bone lining cells - made from osteoblasts along the surface of most bones in an adult. Bone-lining cells are thought to regulate the movement of
calcium and phosphate into and out of the bone 4. Osteogenic cells - respond to traumas, such as fractures, by giving rise to bone-forming cells and bone destroying cells Osteoclasts – bone absorbing cell, large
cells that break down bone tissue, important to growth, healing, and remodeling
Red and Yellow Bone Marrow: the formation of blood cells (hematopoiesis) takes place mainly in the red marrow of the bones. In infants, red marrow is found in the bone cavities. With age, it is largely replaced by
yellow marrow for fat storage. In adults, red marrow is limited to the spongy bone in the skull, ribs, sternum, clavicles, vertebrae and pelvis. Red marrow functions in the formation of red blood cells, white blood
cells and blood platelets.
Microscopic Structure of Compact Bone: 1. Haversian system, or osteon – the structural unit of compact bone 2. Lamellae – weight-bearing, column-like matrix tubes composed mainly of collagen 3. Haversian, or
central canal – central channel containing blood vessels and nerves 4. Volkmann’s canals – channels lying at right angles to the central canal, connecting blood and nerve supply of the periosteum to that of the
Haversian canal 5. Osteocytes – mature bone cells 6. Lacunae – small cavities in bone that contain osteocytes 7. Canaliculi – hair like canals that connect lacunae to each other and the central canal
Structure of Long Bone: 1. Diaphysis - main part of the long bone, Tubular shaft that forms the axis of long bones Composed of compact bone that
surrounds the medullary cavity Yellow bone marrow (fat) is contained in the medullary cavity 2. Epiphyses - expanded ends of long bones , exterior is
compact bone, and the interior is spongy bone , joint surface is covered with articular (hyaline) cartilage, epiphyseal line separates the diaphysis from
the epiphyses
Bone Membranes of Long Bone: 1. Periosteum – double-layered protective membrane, Outer fibrous layer is dense regular CT, Inner osteogenic layer is
composed of osteoblasts and osteoclasts, Richly supplied with nerve fibers, blood, and lymphatic vessels (enter the bone via nutrient foramina), Secured to
underlying bone by Sharpey’s fibers 2. Endosteum – delicate membrane covering internal surfaces of bone
Structure of Short, Irregular, and Flat Bones: Thin plates of periosteum-covered compact bone on the outside with endosteum-covered spongy bone (diploë) on
the inside, Have no diaphysis or epiphysis, Contain bone marrow between the trabeculae
Bone Markings: Bulges, depressions, and holes that serve as: sites of attachment for muscles, ligaments, and tendons, joint surfaces, conduits for blood
vessels and nerves
Projections where Muscles, Tendons and Ligaments attach: 1. Tubercle – small rounded projection 2. Tuberosity – rounded projection, 3. Crest – narrow,
prominent ridge of bone 4. Trochanter – large, blunt, irregular surface 5. Line – narrow ridge of bone 6. Epicondyle – raised area above a condyle 7. Spine –
sharp, slender projection 8. Process – any bony prominence
Projections That Help to Form Joints: 1. Head – bony expansion carried on a narrow neck 2. Facet – smooth, nearly flat articular surface 3. Condyle
– rounded articular projection 4. Ramus – armlike bar of bone
Depressions and Openings: 1. Meatus – canal like passageway 2. Sinus – cavity within a bone 3. Fossa – shallow, basinlike depression 4. Groove –
furrow 5. Fissure – narrow, slitlike opening 6. Foramen – round or oval opening through a bone
Bone Fracture Terminology: 1. Nondisplaced – bone ends retain their normal position 2. Displaced – bone ends are out of normal alignment 3.
Complete – bone in broken all the way through 4. Incomplete – bone is not broken all the way through 5. Compound (open) – bone ends penetrate
the skin 6. Simple (closed) – bone ends do not penetrate the skin
Common Types of Fractures: 1. Linear – the fracture is parallel to the long axis of the bone 2. Transverse – the fracture is perpendicular to the
long axis of the bone 3. Oblique – diagonal breaks across the bone 4. Comminuted – bone fragments into three or more pieces; common in the
elderly 5. Spiral – ragged break when bone is excessively twisted; common sports injury 6. Avulsion – pieces of the bone have been pulled apart 7.
Impacted – opposite of avulsion fractures – a piece of bone is pushed down into another piece of bone 8. Fissure – cracks in the bone 9. Depressed
– broken bone portion pressed inward; typical skull fracture 10. Greenstick – incomplete fracture – one side of the bone breaks and the other side bends; common in children 11. Compression – bone is crushed; common in
porous bones 12. Epiphyseal – epiphysis separates from diaphysis along epiphyseal line; occurs where cartilage cells are dying
Bone Repair Process: 1. Injury – broken blood vessels, hematoma 2. Invasion of blood vessels & generalized cells (2-3 days) 3. Fibroblasts develop (1 week) 4. Chondroblasts
develop 5. Callus forms (4 weeks) 6. Remodeling with osteoclasts (8 weeks)
Sprains: ligaments reinforcing a joint are stretched or torn, partially torn ligaments slowly repair themselves, completely torn ligaments require prompt surgical repair
Cartilage Injuries: The snap and pop of overstressed cartilage Common aerobics injury Repaired with arthroscopic
surgery
Dislocations: occur when bones are forced out of alignment, usually accompanied by sprains, inflammation, and joint
immobilization, caused by serious falls and are common sports injuries, subluxation – partial dislocation of a joint
Skeletal Disorders: 1. Spinal Stenosis - narrowing of the spinal column 2. Achondroplasia - defect in the formation of
cartilage at the epiphysis of long bones (dwarfing) 3. Juvenile Rheumatoid Arthritis - chronic inflammatory diseases involving the joints or other organs in children under 16 4. Ankylosing spondylitis immobility of a joint in the spine 5. Osteosarcoma - malignant sarcoma of bone 6. Osteoporosis - Loss of bone mass that occurs throughout the skeleton. Predisposes people to fractures 7. Disc
Herniation - Rupture of the soft tissue that separates two vertebral bones into the spinal canal 8. Scoliosis - a lateral curvature of the spine.
Muscle Function: Stabilizing joints, Maintaining posture, Producing movement, Moving substances within the
body, Stabilizing body position and regulating organ volume , Producing heat– muscle contraction generates 85%
of the body’s heat
Characteristics of Muscle Tissue: Excitability- receive and respond to stimuli, Contractility- ability to shorten and
thicken , Extensibility- ability to stretch , Elasticity- ability to return to its original shape after contraction or
extension
Skeletal Muscle-attached to the bone, it moves the whole body, nucleus- multiple/ peripheral, voluntary control,
striations-yes, cell shape- cylindrical. Smooth Muscle-On hollow organs, glands and blood vessels,functionCompression of tubes & ducts, Nucleus- single/ central, control-involuntary, no Striations, cell shape:Spindleshaped Cardiac muscle- located in the Heart, function:Heart contraction to propel blood ,nucleus is Central & single
, involuntary control, Striations:yes, cell
shape: branched. Muscle Function Skeletal muscles are responsible for all locomotion Smooth muscle helps maintain blood pressure, and squeezes or propels substances (i.e., food, feces ) through organs Cardiac
muscle is responsible for causing the blood through the body Muscle Similarities Skeletal and smooth muscle cells are elongated and are called
muscle fibers: Muscle contraction depends on two kinds of myofilaments – actin and myosin: Muscle terminology is similar: Sarcolemma –
muscle plasma membrane Sarcoplasm – cytoplasm of a muscle cell. Skeletal Muscles There are nearly 650 muscles attached to the skeleton.
See muscle list for competitions. They work in pairs: one muscle moves the bone in one direction and the other moves it back again. Most
muscles extend from one bone across a joint to another bone with one bone being more stationary than another in a given movement. Muscle
movement bends the skeleton at moveable joints. Muscles are anchored firmly to bone by tendons made of dense fibrous connective tissue
shaped like heavy cords. Though very strong and secure to muscle, tendons may be injured. Attachment to the more stationary bone by tendon
closest to the body or muscle head or proximal is the origin and attachment to the more moveable bone by tendon at the distal end is the
insertion. During movement, the origin remains stationary and the insertion moves. The force producing the bending is always a pull of
contraction. Reversing the direction is produced by the contraction of a different set of muscles. As one group of muscles contracts, the other
group stretches and then they reverse actions. Muscle contractions can be short, single contractions or longer ones. Attachments Muscles
span joints and are attached to bone in at least two places When muscles contract the movable bone, the muscle’s insertion moves toward the
immovable bone – the muscle’s origin Muscles attach: o Directly – epimysium of the muscle is fused to the periosteum of a bone o Indirectly – CT
wrappings extend beyond the muscle as a tendon or aponeurosis
Skeletal Muscle Anatomy Skeletal Muscle: Nerve and Blood Supply; Each muscle is served by one nerve, an artery, and one or more veins ;Each
skeletal muscle fiber is supplied with a nerve ending that controls contraction ; Contracting fibers require continuous delivery of oxygen and
nutrients via arteries; Wastes must be removed via veins;Each muscle is a discrete organ composed of muscle tissue, blood vessels, nerve fibers,
and connective tissue ;Each muscle has thousands of muscle fibers in a bundle running from origin to insertion bound together by connective
tissue through which run blood vessels and nerves. Each muscle fiber contains many nuclei, an extensive endoplasmic reticulu m or
sarcoplasmic reticulum, many thick and thin myofibrils running lengthwise the entire length of the fiber, and many mitochondria for energy.
The three connective tissue wrappings are 1.: Epimysium – an overcoat of dense regular CT that surrounds the entire muscle 2. Perimysium –
fibrous CT that surrounds groups of muscle fibers called fascicles 3. Endomysium – fine sheath of CT composed of reticular fibers surrounding
each muscle The basic functional unit of the muscle fiber is the sarcomere which consists of thick filaments with myosin (protein) molecules
and thin filaments with actin (protein) molecules plus smaller amounts of troponin and tropomyosin. When viewed under the microscope, they
appear as striations of dark A bands and light I bands. The A bands are bisected by the H zone with the M line or band running through the center
of this H zone. The I bands are bisected by the Z disk or line. A sarcomere consists of the array of thick and thin filaments between two Z
disks.Sliding-Filament Model In the thick filaments, myosin molecules contain a globular subunit, the myosin head, which has binding sites for
the actin molecules of the thin filaments and ATP. Activating the muscle fiber causes the myosin heads to bind to actin mole cules pulling the
short filament a short distance past the thick filaments. The linkages break and reform (using ATP energy) further along the thick filaments.
Thus the thin filaments are pulled past the thick filaments in a ratchet-like action. No shortening, thickening or folding of individual filaments
occurs. As the muscle contracts, the width of the I bands and H zones decrease causing the Z disks to come closer together, but there is no change in the width of the A band because the thick filaments do not move. As the muscle relaxes or stretches, the width of the I bands separate as the thin filam ents
move apart but the thick filaments still do not move.
Motor Unit: The Nerve-Muscle Functional Unit A motor unit is a motor neuron and all the muscle fibers it supplies The number of muscle fibers per motor unit can vary from four to several hundred Muscles that control fine movements (fingers, eyes) have small motor units Large weight-bearing
muscles (thighs, hips) have large motor units Muscle fibers from a motor unit are spread throughout the muscle; therefore, contraction of a single motor unit causes weak contraction of the entire muscle
Sequential Events of Contraction Cross bridge attachment – myosin cross bridge attaches to actin filament Working (power) stroke – myosin head pivots and pulls actin filament toward M line Cross bridge detachment – ATP attaches to myosin head and the cross bridge detaches “Cocking” of the
myosin head – energy from hydrolysis of ATP cocks the myosin head into the high energy state Regulation of Contraction In order to contract, a skeletal muscle must: Be stimulated by a nerve ending Propagate an electrical current, or action potential, along its sarcolemma Have a rise in intracellular
Ca2+ levels, the final trigger for contraction Linking the electrical signal to the contraction is excitation-contraction coupling Nerve Stimulus of Skeletal Muscle Skeletal muscles are stimulated by motor neurons of the somatic nervous system
Axons of these neurons travel in nerves to muscle cells Axons of motor neurons branch profusely as they enter muscles Each axonal branch forms a neuromuscular junction with a single muscle fiber Muscle Fatigue – the muscle is in a state of
physiological inability to contract Muscle fatigue occurs when: ATP production fails to keep pace with ATP use, There is a relative deficit of ATP, causing contractures , Lactic acid accumulates in the muscle, Ionic imbalances are present Oxygen
Debt Vigorous exercise causes dramatic changes in muscle chemistry For a muscle to return to a resting state: Oxygen reserves must be replenished, Lactic acid must be converted to pyruvic acid, Glycogen stores must be replaced, ATP and CP
reserves must be resynthesized Oxygen debt – the extra amount of O2 needed for the above restorative processes Heat Production During Muscle Activity Only 40% of the energy released in muscle activity is useful as work The remaining
60% is given off as heat Dangerous heat levels are prevented by radiation of heat from the skin and sweating Muscle and Tendon Injuries : Strains – injuries from overexertion or trauma which involve stretching or tearing of muscle fibers.
They often are accompanied by pain and inflammation of the muscle and tendon. If the injury is near a joint and involves a ligament, it is called a sprain. Cramps – painful muscle spasms or involuntary twitches. Stress-induced muscle tension –
may cause back pain and headaches. Muscular Disorders: 1Poliomyelitis – viral infection of the nerves that control skeletal muscle movement 2. Muscular Dystrophies – most common caused by mutation of gene for the protein dystrophin
which helps in attaching and organizing the filaments in the
sarcomere. Duchenne Muscular Dystrophy and Becker muscular dystrophy are the two most common types. The gene for
dystrophin is on the X chromosome so the disorder is sexlinked. Muscle function is impaired 3. Myasthenia gravis – autoimmune disease affecting the neuromuscular junction. Patients
have smaller end plate potentials due to the antibodies being
directed against the receptors. It affects the ability of the impulse to cause muscle contraction. Administering an inhibitor of
acetylcholinesterase can temporarily restore contractibility 4. Tetanus - a serious bacterial disease that affects your nervous
system, leading to painful muscle contractions, particularly of your jaw and neck muscles - Tetanus can interfere with your
ability to breathe and, ultimately, threaten your life. Tetanus is commonly known as "lockjaw."
Homeostatic Imbalance: Age Related - With age, connective tissue increases and muscle fibers decrease, muscles become
stronger and more sinewy, by age 80, 50% of muscle mass is lost (sarcopenia), regular exercise reverses sarcopenia, aging of
the cardiovascular system affects every organ in the body, atherosclerosis may block distal arteries, leading to intermittent
claudication and causing severe pain in leg muscles
Exercise: helps muscles become more effective and efficient, tendons will become thicker and able to withstand greater force,
high intensity exercise for short duration produces strength, size and power gains in muscles, low intensity exercise for long
durations will give endurance benefits, trained muscles have better tone or state of readiness to respond, exercise promotes good posture enabling muscles to work effectively and helps
prevent injury, during exercise the muscle cells use up more oxygen and produce increased amounts of carbon dioxide, lungs and heart have to work harder to supply the extra oxygen and
remove the carbon dioxide, heart rate also increases in order to transport the oxygenated blood to the muscles, muscle cell respiration increases - more oxygen is used up and levels of
carbon dioxide rise, brain also tells the heart to beat faster so that more blood is pumped to the lungs for gaseous exchange. More oxygenated blood gets to the muscles and more carbon
dioxide is removed.
Integumentary system - consists of the skin, hair, nails, the subcutaneous tissue below the skin, and assorted glands. Functions include protection against injury and infection,
regulates body temperature, sensory perception, regulates water loss, and chemical synthesis
Protection: covers and protects the entire body against injury and infection 1. Physical barriers - continuity of the skin and hardness of keratinized cells, due to the skin’s physical
characteristics such as the keratinized cells and waterproofing properties of the glycolipids, keratin helps waterproof the skin and protec ts from abrasions and bacteria, glycolipids prevent diffusion of water and water-soluble
substances between cells, continuity prevents bacterial invasion, substances that are able to penetrate the skin: Lipid-soluble substances (i.e., oxygen, carbon dioxide, steroids, and fat-soluble vitamins), Oleoresins of certain plants (ex.
poison ivy and poison oak), Organic solvents (ex. acetone, dry cleaning fluid, and paint thinner), Salts of heavy metals (ex. lead, mercury, and nickel) Topical medications as motion sickness patch 2. Chemical barriers - (skin secretion
and melanin) Skin secretions such as sebum, human defensins (antimicrobial peptides), acid mantle of the skin retards bacteria growth and/or kills them, melanin provides protection from UV damage, skin secretions (acid mantle), low
pH and sebum slow bacterial growth on skin surface , human defensin – natural antibiotic, Cathelicidins – proteins that prevent Strep A infection in wounded skin Melanin – chemical pigment that prevents UV damage 3. Biological
Barriers - Langerhans’ cells (members of the dendritic cells family, residing in the basal and suprabasal layers of the epidermis and in the epithelia of the respiratory, digestive and urogenital tracts. They specialize in antigen
presentation and belong to the skin immune system),, macrophages, and DNA Langerhans’ cells in epidermis present antigens to lymphocytes Dermal macrophages (2nd line of defense) – attack bacteria and viruses that have penetrated the epidermis, Langerhans cells and macrophages present
in the skin helps activate the body’s immune system. DNA structure – the electrons in DNA absorb UV radiation and converts it to heat
Temperature Regulation: production of copious amounts of sweat to dissipate heat, when body temperature rises and is hotter than the external environment the blood vessels in the dermal area dilates and sweat glands are stimulated into activity, evaporation of the sweat from skin’s surface
helps dissipate heat from the body, constriction of dermal blood vessels to retain heat, when it is cold outside, the dermal blood vessels constrict and pull the blood away from the skin and keeps it close to the body core to protect crucial internal organs.
Cutaneous Sensations: cutaneous sensory receptors, Meissner’s corpuscles = light touch, Merkel discs = light touch, Pascinian receptors = lies in deeper dermis/hypodermis & detect deep pressure contacts, hair root plexus: sensations from movement of hairs, hair follicle receptors – movement
across the surface of the skin, bare nerve endings: painful stimuli (chemicals, heat, cold) Excretion/Absorption: Elimination of nitrogen-containing wastes (ammonia, urea, uric acid), sodium chloride, and water. It regulates water loss.
Metabolic Functions: Synthesis of Vitamin D – increases calcium absorption in the body, Vitamin D is a fat-soluble vitamin that may be absorbed from the intestines or may be produced by the skin when the skin is exposed to ultraviolet light (particularly sunlight). It is converted to its active form
by the body in 2 steps, occurring first in the liver and completed in the kidneys. In its active form, vitamin D acts as a hormone to regulate calcium absorption from the intestine and to regulate levels of calcium and phosphate in the bones. Vitamin D deficiency causes Rickets (when the body is
deficient in vitamin D, it is unable to properly regulate calcium and phosphate levels) If the blood levels of these minerals becomes low, the other body hormones may stimulate release of calcium and phosphate from the bones to the bloodstream, chemical conversion of many substances, blood
reservoir – preferential shunting of blood as needed
Membranes - thin sheet-like structures that protect parts of the body 1. Serous Membranes - line body cavities that have no opening to the outside, secrete a watery fluid called serous fluid that lubricates surfaces 2. Mucous Membranes - line cavities and tubes that open to the outside 3. Synovial
Membranes - form the inner lining of joint cavities, secrete a thick fluid called synovial fluid 4. Cutaneous Membrane - also known as skin
Characteristics of Skin: The integument covers the entire body and is the largest organ, 2 meters and heaviest organ, 16% of body mass of the body, composed of the epidermis and dermis, pliable, yet durable, thickness: 1.5 to 6.0 mm
Types of Skin: 1. Thin - 1-2 mm on most of the body and 0.5 mm in eyelids, hairy, covers all parts of the body except palms of hands and soles of feet, thin epidermis and lacks stratum lucidum, lacks dermal papillae has more sebaceous glands, fewer sweat glands, s ensory receptors than thick skin
2. Thick - up to 6 mm thick on palms of hands and soles of feet, hairless, covers palms of hands and soles of feet , thick epidermis and a distinct stratum lucidum, epidermal
ridges are present due to well-developed, numerous dermal papillae, lacks sebaceous glands, has more sweat glands, sense receptors are also more densely packed.
Types of Cells in Epidermis: 1. Keratinocytes - 90 % of epidermal cells are keratinized, contains keratin (fibrous protein), protects and waterproofs the skin 2. Melanocytes 8% of the epidermal cells, produces melanin, contributes to skin color and absorbs UV light 3. Langerhans cells - arise from red bone marrow and migrate to the epidermis,
constitute a small portion of epidermal cells, participate in immune responses, easily damaged by UV light 4. Merkel cells - least numerous of the epidermal cells, found in
the deepest layer of the epidermis, along with tactile discs, they function in sensation of touch
Layers of Epidermis: 1. Stratum Corneum - 25-30 layers of dead flat keratinocytes, shed continuously and replaced by cells from the deeper strata, serves as a water,
microbe, injury barrier 2. Stratum Lucidum - present only in thick skin 3-5 layers of clear, flat, dead keratinocytes, dense packed intermediate filaments, thick plasma
membranes 3. Stratum Granulosum - Located above the stratum spinosum, 3-5 layers of flattened keratinocytes undergoing apoptosis, organelles begin to disintegrate
becomes nonliving cells, marks the transition between deeper metabolically active strata and the dead cells of the superficial strata, contains lamellar granules, secretes
lipid-rich secretion that acts as a water sealant 4. Stratum Spinosum - located above the stratum basale, 8-10 layers of keratinocytes, some cells retain their ability for cell
division, cells have spine like projections (bundles of filaments of the cytoskeleton) tightly joins cells to each other, provides skin both strength and flexibility 5. Stratum
basale - also referred to as stratum germinativum because this is where new cells are formed, deepest layer of the epidermis, single row of cuboidal or columnar
keratinocytes
Major difference is that the dermis in the male is much thicker than in the female whereas the epidermis and hypodermis are thicker in the female, thus resulting in total
skin that is 40% thicker in the male.
Growth of epidermis: newly formed cells in the stratum basale undergo keratinization as they are pushed to the surface, they accumulate more keratin during the process,
then they undergo apoptosis, eventually they slough off and are replaced, process takes about 4 weeks, rate of cell division in the stratum basale increases during injury
Dermis: second deepest part of the skin, blood vessels, nerves, glands and hair follicles are embedded
Here, composed mainly of connective tissues (collagen and elastic fibers), collagen fibers make up 70% of the dermis and give structural toughness and strength. Elastin
fibers are loosely arranged in all directions and give elasticity to the skin. Has two layers – Papillary Layer and Epidermal layer.
1. Papillary layer - superficial portion of the dermis, consist of areolar connective tissue containing elastic fiber, surface area is increased due to projections called dermal papillae which contains capillaries or tactile receptors, epidermal ridges conforms
to the dermal papillae
2. Reticular layer - deeper portion of the dermis, consist of dense irregular connective tissue containing collagen/elastic fibers, provides skin with strength and elasticity, contains
hair follicles, nerves, sebaceous and sudoriferous glands
Hypodermis: (subcutaneous), attaches the skin to underlying organs and tissues, not part of the skin - lies below the dermis, contains connective tissue and adipose tissues (subcutaneous fat) for insulation, infants and elderly
have less of this than adults and are therefore more sensitive to cold
Skin Appearances: epidermis appears translucent when there is little melanin or carotene, white skin appears pink to red depending on amount and oxygen content of blood moving in the capillaries of the dermis, albinism is
an inherited trait where a person can’t produce melanin. They have melanocytes but are unable to make tyrosinase (the enzyme which initiates melanin production) so. melanin is missing in their hair, eyes, and skin.
Skin color as diagnostic clues for medical conditions: 1. Cyanotic) Ex: someone who has stopped breathing and the
skin appears bluish because the hemoglobin is depleted of oxygen 2. Jaundice) - Buildup of bilirubin (yellow pigment)
in the blood gives a yellowish, the appearance of eyes and skin indicating liver disease Biliru bin is produced when red
blood cells get old and are broken down by the body. Normally it is processed in the liver and then deposited in the
intestine so it can come out in the stool 3. Erythema - Engorgement of capillaries in the dermis indicating skin injury,
infection, heat exposure, inflammation, allergies, emotional state, hypertension 4. Pallor - paleness, emotional state,
anemia, low blood pressure 5. Bronzing - Addison’s disease, adrenal cortex, too much melanin/melanocyte 6. Bruising
(hematoma)- escaped blood has clotted hematomas , deficiency in Vitamin C or hemophilia 7. Leathery skin overexposure clumping of elastin fibers depressed immune system o can alter DNA to cause skin cancer 8.
Photosensitivity - to antibiotics & antihistamines
Skin Color – genetic factors, environmental factors and volume of blood
Skin Pigments - three pigments are responsible for skin color- melanin, carotene, hemoglobin. 1. Melanin - located
mostly in epidermis, number of melanocytes are about the same in all races, difference in skin color is due to the
amount of pigment that melanocytes produce and disperse to keratinocytes. freckles are caused by the accumulation
of melanin in patches, liver spots are also caused by the accumulation of melanin, melanocytes synthesize melanin
from an amino acid called tyrosine along with an
enzyme called tyrosinase. All this occurs in the melanosome which is an organelle in the melanocyte. Two types of melanin: eu melanin which is brownish black and pheomelanin which is
reddish yellow, fair-skinned people have more pheomelanin and dark skinned people have more melanin
Environmental Factors include UV light increases enzymatic activity in the melanosomes and leads to increased melanin production, tan is achieved because the amount of melanin has
increased as well as the darkness of the melanin. (Eumelanin provides protection from UV exposure while pheomelanin tends to break down with too much UV exposure), melanin provides
protection from the UV radiation but prolonged exposure may cause skin cancer. 2. Carotene (carrot = carrot) - yellow-orange pigment, precursor for Vitamin A which is used to make
pigments needed for vision, found in stratum corneum and fatty areas of dermis and hypodermis layer 3. Hemoglobin - oxygen-carrying pigment in red blood cells
Skin Markings - skin is marked by many lines, creases and ridges, 1. Friction Ridges: markings on fingertips characteristic of primates, allow us to manipulate objects more easily - fingerprints
are friction ridge skin impressions 2. Flexion Lines: on flexor surfaces of digits, palms, wrists, elbows etc skin is tightly bound to deep fascia at these points 3.F reckles: flat melanized patches
vary with heredity or exposure to sun 4. Moles: elevated patch of melanized skin, of the with hair mostly harmless, beauty marks
Aging: beginning in our 20s, the effects of aging begin to be visible in the skin, stem cell activity declines: skin thin, repair difficult, epidermal dendritic cells decrease: reduced immune
response, vitamin D3 production declines: calcium absorption declines and brittle bones, glandular activity declines: skin dries, body can overheat, blood supply to dermis declines: tend to feel cold, hair follicles die or produce thinner hair, dermis thins and becomes less elastic – wrinkles, sex
characteristics fade: fat deposits spread out, hair patterns change, genetically programmed chronologic aging causes biochemical changes in collagen connective tissues that give skin its firmness and elasticity, the genetic program for each person is different, so the loss of skin firmness and
elasticity occurs at different rates and different times in one individual as compared with another, as skin becomes less elastic, it also becomes drier, underlying fat padding begins to disappear, with loss of underlying support by fat padding and connective tissues, the skin begins to sag. It looks
less supple and wrinkles form, skin may be itchy with increased dryness, and a cut may heal more slowly.
Derivatives of skin: during embryonic development thousands of small groups of epidermal cells from stratum basale push down into dermis to form hair follicles and glands
Skin receptors: your skin and deeper tissues contain millions of sensory receptors, most of your touch receptors sit close to your skin's surface. 1. Light touch - Meissner's corpuscles are enclosed in a capsule of connective tissue,
react to light touch and are located in the skin of your palms, soles, lips, eyelids, external genitals and nipple, These areas of your body are particularly sensitive 2. Heavy pressure - Paccinian corpuscles sense pressure and vibration
changes deep in your skin, every square centimeter of your skin contains around 14 pressure receptors
3. Pain - skin receptors register pain, pain receptors are the most numerous, each square centimeter of your skin contains around 200 pain receptors 4. Temperature - skin receptors register warmth and cold, each square centimeter
of your skin contains 6 receptors for cold and 1 receptor for warmth, cold receptors start to perceive cold sensations when the surface of the skin drops below 95F. They Are most stimulated when the surface of the skin is at 77F and
are no longer stimulated when the surface of the skin drops below 41F. This is why your feet or hands start to go numb when the y are submerged in icy water for a long period of time. Hot receptors start to perceive hot sensations
when the surface of the skin rises above 86 o F and are most stimulated at 113F. Beyond 113F, pain receptors take over to avoid damage being done to the skin and underlying tissues, Thermoreceptors are found all over the body, but
cold receptors are found in greater density than heat receptors – most of the time our environment is colder than our body temperature, highest concentration of thermoreceptors can be found in the face and ears so your nose and
ears always get colder faster than the rest of your body on a chilly winter day
Anatomy of Hair Follicle: 1. Shaft: portion of hair that projects from skin surface, straight hair has a round shaft, curly hair is oval 2. Root: portion of hair deep to the shaft penetrating the dermis, Has 3 layers = medulla: contains
pigment granules and air spaces, cortex: middle layer in dark hair contains pigment in gray or white hair contains air bubbles cuticle: outer laye r, heavily keratinized cells that lie like shingles, Base of the hair follicle = 1. Bulb: houses
the papilla which contains the blood vessels that
nourishes the growing hair follicle. 2. Matrix: responsible for hair growth and produces new hair Arrector pili: smooth muscle - extends from the dermis to the side of hair follicle, hair grows at an angle to the surface of the skin,
arrector pili muscles contract and pulls hair straight causing goosebumps. Hair root plexus - dendrites of neurons which are sensitive to touch
Important Features and Texture: roughly 5 million hairs cover the body of an average individual, about 100,000 are on the scalp, almost every part of body is covered with hair except palms of hands, soles of feet, sides of fingers
and toes, lips and parts of genitals, hair shafts differ in size, shape, and color. In the eyebrows they are short and stiff while on the scalp they are longer and more flexible, over the rest of the body they are fine and nearly invisible,
oval shaped hair shafts produce wavy hair, flat or ribbon-like hair shafts produce curly or kinky hair, and round hair shafts produce straight hair.
Skin Glands: 1. Sudoriferous: sweat glands, 3- 4 million glands in your body empties onto the skin thru pores or into hair follicles. Two main types of sweat glands = 1. Eccrine sweat glands - secretes cooling sweat, secretes directly
onto the skin, began to function soon after birth, sweat is composed of 98 percent water and two percent dissolved salts and nitrogenous wastes such as urea and uric acid, helps regulate body temperature/aids in waste removal
2. Apocrine sweat glands - stimulated during emotional stress/excitement, secretes into hair follicle, begins to function at puberty, slightly more viscous than eccrine secretions, composed of the same components as eccrine sweat plus, lipids and proteins, referred to as “cold sweat”.
2. Sebaceous: oil glands, they are mostly
connected to hair follicles. sebaceous glands are embedded in the dermis over most of the body. absent in the palms and soles , vary in size, shape and numbers in other areas of the body, secrete an oily
substance called sebum which lubricates the hair and skin, mixture of fats, cholesterol, proteins, inorganic salts, pheromones, coats surface of hair, prevents excessive evaporation of water from skin, keeps
skin soft and pliable, inhibits growth of some bacteria, sebaceous gland activity increases with puberty, due to the male and female hormone activity, accumulation of sebum in the ducts = white pimples – if the
sebum darkens -black heads form, acne - inflammation of sebaceous gland ducts
3. Ceruminous: modified sweat glands of the external ear that produce ear wax, open directly onto the surface of the external auditory canal (ear canal) or into ducts of sebaceous glands, earwax is the
combination of secretion of ceruminous and sebaceous glands, earwax and the hair combine to provide a sticky barrier against foreign items.
Hair Growth Cycle: hair follicles grow in repeated cycles, three phases. 1. Anagen - Growth Phase 2. Catagen – Transitional Phase 3. Telogen - Resting Phase, each hair passes through the phases independent of
the neighboring hairs 1. Anagen Phase - Growth Phase = approximately 85% of all hairs are in the growing phase at any one time. The Anagen phase or growth phase can vary from two to six years. Hair grows
approximately 10cm per year and any individual hair is unlikely to grow more than one meter long. Each hair on your body grows from its own individual hair follicle. Inside the follicle, new hair cells form at
the root of the hair shaft. As the cells form, they push older cells out of the follicle. As they are pushed out, the cells die and become the hair we see, a follicle will produce new cells for a certain period of time
depending on where it is located on your body. This period is called the growth phase 2. Catagen Phase - Transitional Phase = at the end of the Anagen Phase the hairs enters into a Catagen Phase which lasts
about one or two weeks, during the
Catagen Phase the hair follicle shrinks to about 1/6 of the normal length, The lower part is destroyed and the dermal papill a breaks away to rest below 3.
Telogen Phase - Resting Phase =normally lasts about 5-6 weeks. During this time the hair does not grow but stays attached to the follicle while the dermal papilla stays in a resting phase below. Approximately 10-15 percent of all hairs are in
this phase at any one time, when the hair follicle enters the Resting Phase, the hair shaft breaks, so the existing hair falls out and a new hair takes its place. Therefore, the length of time that the hair is able to spend growing during the growth
phase controls the maximum length of the hair. The cells that make the hairs on your arms are programmed to stop growing every couple of months, so the hair on your arms stays short. The hair follicles on your head, on the other hand, are
programmed to let hair grow for years at a time, so the hair can grow very long, animals that shed have hair follicles that synchronize their rest phase so that all o f the follicles enter the rest phase at once, some factors that affect the rate of
growth and replacement of hair are illness, diet, stress, gender, radiation therapy, and medication, at the end of the Telogen phase the hair follicle re-enters the Anagen Phase. The dermal papilla and the base of the follicle join together again
and a new hair begins to form. If the old hair has not already been shed the new hair pushes the old one out and the growth cycle starts all over again.
Skin Imbalances - The skin can develop >1000 different ailments. the most common skin disorders result from allergies or infections less common are burns and skin cancer
Skin lesions – any measurable variation from normal structure of the skin 1. Elevated lesions – cast a shadow outside the edges as warts, plaque, blister 2, Flat lesions – do not cast a shadow as a scab, elevated lesion with pus, hive 3. Depressed
lesions – cast a shadow within their edges as lacerations, ulcers, fissures
Infections: 1. Viral - eg. cold sores, herpes simplex especially around lips and oral mucosa, Warts – benign neoplasms caused by papillomavirus (HPV) 2. Fungal - eg. athletes foot, Tinea 3. Bacterial- eg. boils and carbuncles inflammation of hair
follicle and sebaceous glands especially on face or dorsal side of neck , impetigo Streptococcus infection
***Contact dermatitis is a condition in which the skin becomes red, sore, or inflamed after direct contact with a substance. There are two kinds of contact dermatitis: irritant or allergen Irritant dermatitis is the most common type. It's caused by
contact with acids, alkaline materials such as soaps and detergents, fabric softeners, solvents, or other chemicals. The reaction usually looks like a burn.
Treatments: washing with lots of water to remove any traces of the irritant that may remain on the skin, avoid further exposure to known irritants or allergens, anti-itch (antipruritic) or drying lotions may be recommended to reduce other symptoms, corticosteroid skin creams or ointments may
reduce inflammation, corticosteroid pills or a corticosteroid shot from the doctor may be needed in severe cases
Genetic Diseases: 1. Psoriasis - chronic, noninfectious skin disease, skin becomes dry and scaly, often with pustules and many varieties o cycle of skin cell production increases by 3-4x’s normal, stratum corneum gets thick as dead cells accumulate, seems to be a genetic component, often triggered
by trauma, infection , hormonal changes or stress 2. Vitiligo – a autoimmune pigmentation disorder where melanocytes in the epidermis are destroyed (Michael Jackson)
Burns: 1st degree burns - skin is inflamed, red - surface layer of skin is shed, 2nd degree burns - deeper injury - blisters form as fluid builds up beneath outer layers of epidermis, 3rd degree burns - full thickness of skin is destroyed -sometimes even subcutaneous tissues results in ulcerating
wounds, typically results in catastrophic loss of fluids (dehydration, electrolyte imbalances), highly susceptible to infections, slow recovery (from cells of hair follicles if they survive; otherwise must heal from
margins of wound), may require: autografts, cadaver skin, pig skin, prognosis may depend on extent of damage, A fourth degree burn additionally involves injury to deeper tissues, such as muscle or bone
Skin Cancer: cells have a built-in mechanism that causes contact inhibition. Healthy cells stop growing when they come in contact with one another. In damaged cells, contact inhibition is lost and therefore the cells continue to grow until they start jumping up on one another, do not exhibit contact
inhibition, excessive or chronic exposure UV radiation , x-rays or radiation’ chemicals or physical trauma are predisposing factors to cancer, most forms progress slowly and are easily treated but a few are deadly. 1. Basal Cell Carcinoma - least malignant, most common -78% of all skin cancer,
stratum basale can’t form keratin, lose boundary layer between epidermis and dermis, results in tissue erosion and ulceration, 99% of these cancers are fully cured 2. Squam ous Cell Carcinoma - 20% of all skin cancers cancer of the cells in stratum spinosum arise from squamous cells of the
epidermis, usually induced by sun, cells grow rapidly and grow into the lymphatic tissues, hardened small red growth, spreads rapidly if not removed, good chance of recovery if detected and treated early 3. Malignant Melanoma - cancer of pigment cells = melanocytes, rare ~1% of skin cancers,
deadly, poor chance of cure once it develops, often begins with moles, spreads rapidly, early detection and treatment is the key to survival