Exam 3 Flashcards
the body’s largest organ in terms of surface area and weight.
The skin
Skin would cover
1.5 to 2.0 square meters if surface area if flattened into a sheet
Skin makes up approximately ____ of your total body weight
15%
Organization of the skin
consists of a superficial epidermis and a deeper dermis; below this is the hypodermis, which is a layer of connective tissue.
thickness of skin
1mm to 2mm thick; ranges from 0.6 mm in eyelids to 6.0 mm on back
thick skin
has five epidermal layers and covers the palms, soles, fingers, and toes with a surface layer of dead cells and it lacks hair follicles
thin skin
has four thinner epidermal layers and covers all other parts of the body
Dermatology
the study and treatment of the integument and the appearance and/or condition of one’s skin can provide diagnostic information regarding one’s overall health.
organization of the epidermis
consists of keratinized stratified squamous epithelium that is organized into several distinct strata.
blood supply of epidermis
it contains no blood vessels, so its cells depend on diffusion of oxygen and nutrients from blood vessels in underlying connective tissue
The stratum basale
consists of a single layer of cuboidal or columnar cells that continuously undergo mitotic cell division to produce new skin cells.
keratinocytes
the most abundant cells and are held together by desmosomes
helps to waterproof skin
Tough, fibrous keratin protects skin from heat, microbes, chemicals
melanocytes
synthesize the pigment melanin
melanin
responsible for skin color and it absorbs ultraviolet radiation to protect skin from damaging effects of sunlight
Merkel cells
touch receptors that join with sensory neurons to form Merkel discs
The stratum spinosum
consists of several layers of keratinocytes.
when skin is prepared for microscope slides,
keratinocytes shrink and pull apart, except where attached by desmosomes
dendritic (Langerhans) cells
macrophages that a rise in bone marrow and migrate to the epidermis to protect body against microbes that invade skin
The stratum granulosum
consists of keratinocytes that contain dark-staining granules of protein that eventually become keratin.
as keratinocytes flatten,
the nucleus and organelles disintegrate and granules of keratin accumulate in the cytoplasm
the outer limit for diffusion of substances
the stratum granulosum
The stratum lucidum
a thin, translucent layer of dead cells found only in thick skin.
The stratum corneum
contains up to 30 layers of dead, scaly keratinized cells and makes up about 75% of the thickness of the epidermis.
it takes ________________ for a keratinocyte to migrate to the skin’s surface and exfoliate
30 to 40 days
most household dust is made up of
dander
the presence of dander in bedding provides food for
dust mites
an allergy to household dust is actually an allergy
to the feces of dust mites
persistent friction with the stratum corneum layer can cause
a thickened callus to form
organization of the dermis
consists of connective tissue comprised mainly of collagen fibers, but elastic fibers, reticular fibers, fibroblasts, and macrophages are also present.
dermal papillae.
The boundary between the dermis and the epidermis
these finger-like projections of the dermis extend into the epidermis to form epidermal ridges on the palms, fingers, soles, and toes; they increase grip by increasing friction
dermal papillae.
The papillary layer
a superficial zone comprised of areolar connective tissue that contains elastic fibers.
The papillary layer contains
capillaries, touch receptors (Meissner’s corpuscles), and numerous free nerve endings
The reticular layer
a deep zone comprised of dense irregular connective tissue that contains collagen bundles.
The reticular layer contains
adipocytes, hair follicles, nerves, oil glands, and the ducts of sweat glands
provide the skin with strength, extensibility, and elasticity
collagen fibers and elastic fibers
stretch marks
Small tears may occur during pregnancy or as result of obesity; produce silvery white stretch marks on thighs, buttocks, abdomen, breasts
subcutaneous hypodermis or superficial fascia
Beneath the dermis
the subcutaneous hypodermis consists of
areolar connective tissue and adipose tissue
functions of the subcutaneous hypodermis
binds skin to underlying tissue, cushions body, provides thermal insulation, stores energy
blood supply of the subcutaneous hypodermis
numerous blood vessels supply the skin with oxygen and nutrients and provide pathway for rapid absorption of drugs and/or medicines into bloodstream
Pacinian corpuscles
nerve endings in the subcutaneous hypodermis that are sensitive to pressure
Skin color is determined by
genes that control the interaction of melanin, carotene, and hemoglobin.
Melanin produces
variations in skin color that range from pale yellow to black.
exposure to ultraviolet radiation in sunlight
stimulates melanocytes to increase their production melanin so skin becomes darker
differences in skin color
due primarily to differences in amount of melanin produced (all races have approximately the same number of melanocytes)
melanin tends to be most plentiful in
face, limbs, around nipples, and external genitalia
in people with dark skin,
melanin breaks down slowly making it visible in all epidermal layers
in people with light skin
melanin breaks down rapidly making it less visible beyond stratum basale
freckles
flat patches of skin where melanin accumulates
moles
elevated patches of skin where melanin accumulates
vitiligo
results from partial or complete loss of melanocytes in patches of skin and produces irregular white blotches
Carotene
a yellow-orange pigment that accumulates in the stratum corneum or sub-cutaneous fat, which gives the skin a yellowish tint.
If there are small amounts of melanin and carotene
the epidermis becomes translucent.
hemoglobin molecules in the blood
become visible, which produces the pinkish flesh tones that are typical of Caucasian skin
Erythema
describes abnormal redness due to the dilation of dermal blood vessels during strenuous exercise or heat or anger or embarrassment.
Cyanosis
describes blueness of the skin due to insufficient oxygen in the blood because of airway obstructions or lung disease or cold weather.
Jaundice
a yellowing of the skin and the whites of the eyes due to elevated levels of bilirubin in the blood because the liver is unable to dispose of the excess bilirubin.
Pallor
describes pale skin due to reduced dermal blood flow because of low blood pressure or shock or anemia or emotional stress.
Albinism
a genetic defect that results in a lack of the amino acid tyrosine, which blocks the synthesis of melanin and produces pale skin, white hair, and pink eyes.
hematoma
a visible blood clot caused by trauma to the skin, which produces a bruise.
hemangiomas
“birthmarks” caused by benign tumors of dermal blood vessels
Hair (pili) covers
all skin surfaces except for the palms, soles, eyelids, lips, and nipples.
probably vestigial and has no essential function,
human hair
scalp hair
reduces heat loss and provides protection from ultraviolet radiation
eyebrows
enhance facial expression and non-verbal communication
eyelashes
shield the eyes from rain and windblown debris
guard hairs
prevent foreign particles from entering the nostrils or ear canals
Each hair consists of
columns of dead, keratinized cells that are fused together.
hair shaft
portion of a hair above the skin surface
hair root
deep to the shaft and is surrounded by a tube called the follicle
hair bulb
a swelling at the base of the follicle from which a hair originates
papilla
contains blood vessels to nourish hair
Each hair has _____ layers
three
inner medulla
contains air spaces
cortex
consists of densely packed keratinized cells
cuticle
a single layer of overlapping scaly cells; as cuticles wear away, keratin fibrils spill out of cortex and medulla causing ‘split ends’ to develop
Hair texture is related to
the cross-sectional shape of the hairs and hair color is due to the type and amount of pigment in each hair.
if the hair shafts are flat and ribbon-like
the hair becomes “kinky”
if the hair shafts are oval
the hair becomes “silky/wavy”
if the hair shafts are round
the hair becomes “straight/coarse”
Gray and white hair
lack melanin in cortex and have air bubbles in shaft
Red hair
colored by iron-containing pigment
coarse, long hair of eyebrows and scalp is
terminal hair
terminal hair
grows in response to testosterone,so it appears in auxiliary and pubic regions when males and females go through puberty
Hair growth follows
a cycle.
stem cells from the follicle
multiply and push the papilla deeper into the skin
cells in the root sheath
transform into hair cells that synthesize keratin
as they push upward away from papilla
the hair dies
a hair goes into a
resting stage and will eventually fall out
Normal adult hair loss
50-100 hairs per day
scalp hairs grow about
1 mm every three days with an annual growth of 10 to 18 cm
alopecia
hair loss; hair growth slows down around age 40 and alopecia occurs because of aging or disease or poor nutrition or medical treatment
pattern baldness
genetic condition expressed in individuals with high testosterone
An arrector pili muscle
consists of smooth muscle and is associated with each hair.
cold temperatures, fright, or emotional stress
can cause these muscles to contract and pull a hair into a vertical position producing ‘goose bumps’
Nails
plates of hard, keratinized cells that form protective coverings over the dorsal surface of the terminal portion of the fingers and toes.
The visible portion of a nail is the
nail body
the hidden portion of a nail is the
nail root
portion of the nail that extends beyond the end of the digit is the
free edge
a small white area at the proximal end of the nail body
lunule
dead epidermis that covers the proximal end of the nail
cuticle
Nail growth occurs by
mitosis from the nail matrix at a rate of about 1 mm per week.
Sebaceous (oil) glands
usually connected to hair follicles, although some of them open directly to the surface of the skin.
keep hair from drying out and turning brittle, to keep skin soft and moist, to inhibit growth of certain bacteria
an oily sebum secreted by oil glands
accumulation of sebum in facial sebaceous glands
causes blackheads which can lead to formation of pimples if they become infected with bacteria
Ceruminous glands
modified sweat glands in the outer ear canal that produce a waxy secretion called cerumen to provide a sticky barrier against the entrance of foreign bodies.
Sudoriferous (sweat) glands
produce a mixture of water, salts, and organic compounds.
sweat
regulates body temperature by providing a cooling mechanism; it also eliminates urea, lactic acid, ammonia, and some drugs from the body
between 3 and 4 million eccrine sweat glands
distributed throughout the skin, especially in palms, soles, forehead; they produce watery perspiration
apocrine sweat glands
located in armpits, pubic area, breasts, and beard area of mature males where their ducts lead to nearby hair follicles rather than to the surface of the skin
apocrine glands produce a viscous perspiration
contains organic substances that can be source of body odor
development of apocrine glands
do not develop until puberty and respond to emotional stress or sexual arousal
apocrine glands in females
these glands enlarge and shrink during the monthly menstrual cycle
Skin
provides a protective physical barrier against abrasion.
anti-bacterial substances
bacteria have trouble multiplying because of anti-bacterial substances that are present in sebum and sweat
Bacteria that invade skin are attacked by
macrophages and leukocytes
keratin
waterproof nature of keratin prevents dehydration and absorption of excess water
melanin
provides some protection against damage from ultraviolet radiation
Transdermal absorption
the ability to absorb drugs and/or chemicals across the epidermis.
nitroglycerine
can be absorbed to relieve heart pain
scopolamine
can be absorbed to reduce motion sickness
nicotine patches
can be used to quit smoking
hormones
can be absorbed for purposes of birth control
toxins
from poison ivy, organic solvents, and metal salts can be easily absorbed
Exposure to ultraviolet light
helps the skin convert a form of cholesterol into vitamin D.
Vitamin D
aids in absorbing calcium and phosphorous from food
Perspiration
eliminates some organic wastes, salts, and water from the body.
Nerve endings
can detect stimuli that get interpreted as touch, pressure, temperature, or pain.
The regulation of body temperature by the skin and other organs is a great example of
homeostasis
Excessive heat
triggers thermoreceptors in the skin to send nerve signals to a temperature control region in the hypothalamus of the brain.
signals send to temp control regions
cause sweat glands to increase perspiration which cools body as sweat evaporates;dermal blood vessels dilate and blood flow increases so more heat can be released
Extreme cold
triggers thermoreceptors in the skin to send nerve signals to the temperature control region in the hypothalamus.
hypothalamus
sends signals to dermal blood vessels that reduce blood flow to conserve heat
involuntary contractions of skeletal muscles
cause shivering,which produces heat to compensate for loss if heat from body’s surface
Regeneration
replaces dead or damaged cells resulting from cuts, scrapes, and/or burns with the same cell type in order to restore normal function to the tissue
fibrosis
replaces damaged tissue with scar tissue that consists mainly of collagen fibers, so normal function gets altered
During an inflammatory phase
mast cells escape from damaged blood vessels and release histamine in order to increase blood flow to the site of the wound.
During a migratory phase
a blood clot forms and scabs over to temporarily seal the wound.
macrophages
enter the wound and phagocytize cellular debris
During a proliferative phase
new blood capillaries develop.
fibroblasts
deposit collagen fibers into the blood clot filling the wound with granulation tissue
During maturation phase
surface epithelial cells multiply and loosen scab until it eventually falls off.
the leading cause of skin cancer
Excessive exposure to sunlight; fair-skinned people and the elderly are most susceptible.
Basal cell carcinoma
the most common type of skin cancer, but the least dangerous.
Basal cell carcinoma tumors
arise from pre-cancerous cells in the stratum basale, but rarely metastasize
Squamous cell carcinoma
less common and will metastasize if neglected.
Squamous cell carcinoma tumors
arise from keratinocytes in the stratum spinosum of scalp, ears, or back of hand; often from pre-existing skin lesions on sun- damaged skin
Malignant melanoma
the least common, but metastasizes quickly and can be fatal.
most prevalent type of life-threatening cancer among young women
Malignant melanoma
Malignant melanoma tumors
often arise from malignant melanocytes in a pre-existing mole
successful treatment depends on early detection (malignant melanoma)
A - asymmetry of mole
B - irregular border of mole
C - uneven and multiple coloration
D - diameter greater than 1/4 inch
Risk factors for skin cancer:
individuals with fair skin who tend to burn rather than tan
excessive exposure to sun and frequent occurrences of severe sunburn
family history of skin cancer
individuals who have a suppressed immune system
Tissue damage to the integument
destroys the protection afforded by the skin because it permits microbial invasion, infection, fluid loss, and loss of thermoregulation.
First-degree burns
characterized by redness and pain in the surface epidermis.
first degree burn healing
takes a few days and may be accompanied by peeling or flaking
example of first degree burns
most sunburns
Second-degree burns
destroy the entire epidermis and at least parts of the dermis; characterized by redness, blister formation, fluid accumulation, and pain
second degree burn healing
takes several weeks and mild scarring may occur
Third-degree burns
destroy the epidermis, dermis, and even parts of the hypodermis;
third degree burn pain
loss of sensory nerve endings actually limit pain
Third-degree burns excessive fluid loss
can lead to massive infection
Third-degree burns regeneration
slow, grafting may be necessarym considerable scarring occurs
Bones are classified as
organs because they consist of osseous tissue and also contain cartilage, fibrous connective tissue, and nervous tissue.
The skeleton provides
a framework that supports the soft tissues of the body; protection; and surfaces for muscle attachments that are needed to move the body.
bones that protect examples
Cranium protects brain; vertebral column protects spinal cord; bony thorax protects heart and lungs; pelvic girdle protects reproductive and urinary organs
hemopoiesis
The skeleton carries out hemopoiesis, by which red bone marrow produces blood cells.
The skeleton stores
calcium, phosphorus, and other minerals needed for homeostasis; and stores energy in the adipose tissue found in yellow bone marrow.
Long bones
have greater length than width and they are slightly curved for strength.
_______________ is prevalent, but _________________ is present at both ends
compact bone; spongy bone
distal and proximal ________________ are separated by a ___________________
epiphyses (ends); diaphysis (shaft)
long bone shaft covering
covered by a tough periosteum with fibrous layer of dense irregular connective tissue and osteogenic layer containing bone-forming cells
Periosteum
protects bone, helps nourish bone tissue, assists in repairing functions
medullary cavity
runs the length of the diaphysis; filled with bone marrow
red marrow
found at the ends of long bones; blood cells get produced
yellow marrow
has adipose tissue for energy; can change to red marrow
endosteum
comprised of reticular CT and lines medullary cavity
articular cartilage
covers the epiphyses to provide friction-free movement in a joint
Examples of long bones
humerus, radius, ulna, femur, tibia, fibula
Short bones
tend to be cube-shaped and they have nearly equal length and width.
spongy bone is surrounded by a thin layer of
compact bone
Examples of short bone
carpals in wrist, and tarsals in ankle
Flat bones
thin, bony plates that provide extensive areas for muscle attachment.
parallel plates of compact bone enclose a spongy ________ filled with red marrow
diploe
Examples of flat bones
cranial bones, sternum, ribs, scapulae
Irregular bones
come in a variety of odd shapes; tend to vary in the amount of compact bone and spongy bone
Examples of irregular bones
vertebrae, and some facial bones
Osteogenic cells
stem cells in the periosteum and in the endosteum that differentiate into osteoblasts.
Osteoblasts
bone-forming cells that secrete the collagen fibers and organic matter that is needed to calcify bone tissue.
Osteocytes
mature bone cells that are derived from osteoblasts.
Function of osteocytes
maintain the daily cellular activities of bone tissue, such as nutrient exchange and waste exchange
Osteoclasts
bone-dissolving cells that function in bone resorption and remodeling.
Bone matrix contains
inorganic hydroxyapatite for calcification or mineralization of bone.
responsible for bone hardness
Crystallized calcium phosphate
responsible for bone flexibility.
collagen and other proteins in the bone matrix
Compact bone
arranged in functional units called osteons (Haversian systems) that function like tiny, weight-bearing “pillars”.
central (Haversian) canals
runs the entire length of an osteon and contains blood vessels and nerve fibers.
perforating (Volkmann) canals
link the blood vessel and nerves in a central canal with blood vessels and nerves in the medullary cavity and periosteum
Concentric lamellae
rings of hard, calcified material around a central canal.
Lacunae
tiny spaces between the lamellae and they contain osteocytes.
Canaliculi
tiny channels that connect lacunae, so osteocytes can distribute nutrients to one another and transfer wastes to nearby blood vessels
The lamellae in spongy bone
arranged in a network of bony trabeculae plates.
spaces between the trabeculae in spongy bone
are filled with red bone marrow, which provides nourishment to osteocytes located in lacunae
benefits of spongy bone
provides considerable strength without additional weight and it is the only location for the red bone marrow that produces blood cells in adults
Intramembranous ossification
bone formation directly on or in embryonic fibrous connective tissue membranes.
Bones formed by Intramembranous ossification
Forms flat bones of skull, mandible, clavicles
Mesenchyme cells cluster together and differentiate into
osteogenic cells, which become osteoblasts and start to form a center of ossification
secrete an organic bone matrix until they are completely surrounded
osteoblasts
Matrix secretion stops and osteoblasts become
osteocytes, which deposit calcium phosphate and other mineral salts until the matrix calcifies.
Bone matrix develops into trabeculae that fuse together and create
spongy bone.
creabsorb and remodel this bone to form spaces that fill with red marrow
osteoclasts
Trabeculae at the surface calcify until the spongy bone gets replaced by
compact bone.
mesenchyme at the surface condenses to form the
periosteum
Endochondral ossification
bone formation within a hyaline cartilage model.
Bones formed by Endochondral ossification
Forms most bones of skeleton, including vertebrae, pelvis, limbs
Begins about 6 weeks into embryonic development and continues until age 20
Endochondral ossification
At the site of a future bone, ________________ crowd together and differentiate into chondroblasts, which produce a matrix of hyaline cartilage.
Mesenchyme cells
develops and produces chondrocytes to thicken cartilage
Peridchondrium
Endochondral Ossification- Chondrocytes in the center
grow and burst, releasing chemicals that trigger calcification.
calcification
blocks nutrients from reaching the chondrocytes, so many of them die and leave small cavities in matrix that eventually join together into one large cavity
Blood vessels grow into the deteriorating cartilage to form a ___________________________________ and stem cells give rise to osteoblasts and osteoclasts
Primary ossification center
cartilage erosion in primary ossification centers
occurs from the outside of a bone inward during primary ossification
Cartilage in the shaft is replaced with compact bone, except for the marrow-filled medullary cavity, and _______________________________ develop in both epiphyses as blood vessels infiltrate them near the time of birth.
secondary ossification centers
cartilage erosion in secondary ossification centers
occurs from the center of the epiphysis outward during secondary ossification as osteoblasts form thin trabeculae of spongy bone
ultimately replaces all of the cartilage, except for the hyaline cartilage that covers the epiphyses to become the articular cartilage.
bone
Bones increase in length by ________________ during childhood.
interstitial growth
do not function in actual bone growth, but anchor the epiphyseal plate to the epiphysis
chondrocytes in the zone of reserve cartilage
divide by mitosis and replace chondrocytes that have died on the shaft side of the epiphyseal plate and form long columns with flattened lacunae
chondrocytes in the zone of proliferation
stop dividing and become mature; increases length of shaft
chondrocytes in the zone of hypertrophy
At the end of puberty, cartilage cells stop dividing, bone replaces the cartilage, and the epiphyseal plate fades away until all that remains is a
thin epiphyseal line.
Mature bone continues to thicken for many years by
appositional growth.
osteogenic cells in the periosteum
differentiate into osteoblasts and secrete bone matrix, which causes original periosteum to become endosteum
bone deposition
occurs at the outer surface and bone dissolving occurs at the inner surface to increase bone thickness and enlarge marrow cavity, respectively
Bones are continually remodeled throughout one’s life by absorbing old bone and depositing new bone, which replaces about _____of the skeletal tissue each year.
10%
Bone growth and maintenance depend on
adequate dietary intake of calcium, phosphorus, vitamins, plus human growth hormone, thyroid hormones, insulin, and sex steroids.
Mineral deposition
transfers calcium and phosphate from blood plasma to bone tissue.
bone stores about ____ of the body’s calcium and ______ of the body’s phosphorus
99%; 85%
ectopic (‘out of place’) ossification
describes abnormal calcification of tissues in lungs or brain or muscles or tendons or arteries that produces calculi
Mineral resorption
occurs when osteoclasts dissolve bone tissue and release the minerals into the blood and make them available for other metabolic processes.
secrete hydrogen ions into the extracellular fluid and chloride ions follow them to form hydrochloric acid that dissolves minerals in bone
osteoclasts
osteoclasts secrete acid ______________, which digests collagen fibers in bone matrix
phosphatase
blood levels of calcium must be carefully regulated to maintain
homeostasis
Calcitriol
a derivative of vitamin D and it raises blood levels of calcium; increases calcium absorption from the small intestine
increases the activity of osteoclasts to promote bone resorption
weakly promotes the reabsorption of calcium from urine
Parathyroid hormone (PTH)
is secreted by the parathyroid glands to raise blood levels of calcium.
increases the activity of osteoclasts to promote bone resorption
promotes the reabsorption of calcium from urine
inhibits collagen synthesis by osteoblasts which inhibits bone deposition
Calcitonin
secreted by the thyroid gland to lower blood levels of calcium, but it has a relatively weak effect in an adult.
reduces the activity of osteoclasts to decrease bone resorption
increases the activity of osteoblasts to deposit more calcium into bone
Hypocalcemia
describes a deficiency of calcium in the blood that can lead to muscle tremors, muscle spasms, and the inability of a muscle to relax.
Hypercalcemia
describes an excess of calcium in the blood that can lead to muscle weakness and even cardiac arrest.
Bone can become stronger as it responds to
mechanical stress.
production of collagen fibers and deposition of mineral salts __________
increases
calcitonin production is _________ to inhibit bone resorption
increased
without mechanical stress, bone resorption occurs______________ than bone formation
faster
Bone becomes____________ because of demineralization and reduction of collagen fibers
weaker
The main mechanical stresses on bone are
contracting skeletal muscles and gravity.
individuals who cannot move or astronauts who spend long periods without gravity may lose up to
1% of their bone mass per week
Athletes repeatedly stress their bones, so the bones become
notably thicker and stronger.
weight-bearing exercise builds
bone mass that can be retained as we grow older
Fracture
refers to any break in a bone, and is classified according to the nature of the bone damage.
fracture healing
takes 8 to 12 weeks if a fracture is uncomplicated, but much longer for complex fractures and fractures among older patients
fracture hematoma
When a bone breaks, blood escapes from broken vessels in the bone and periosteum and forms a blood clot, called a fracture hematoma, within six to eight hours after the injury.
The fracture hematoma is invaded by
fibroblasts that produce granulation tissue.
collagen fibers and fibrocartilage form
a soft callus within a couple of days to bridge broken ends of bones
Osteogenic cells
develop into osteoblasts and produce spongy bone trabeculae that join living and dead bone fragments together, forming a hard callus within one week.
A hard callus
persists for 3 to 4 months, while osteoclasts dissolve dead bone fragments.
replaces the spongy bone and remodels the callus until slight thickening remains at fracture site
compact bone
Most fractures are treated by
closed reduction, which manipulates bone fragments into normal position without surgery
open reduction
requires that bone fragments be surgically exposed so screws or pins or plates can be inserted to correctly align the bones
Osteoporosis
characterized by decrease in bone mass and increased susceptibility to fracture.
outpaces bone deposition
bone resorption
is more metabolically active than compact bone and has more surface area upon which osteoclasts can work
spongy bone
Osteoporosis affects
the entire skeletal system, especially vertebral bodies, ribs, the head of the femur, the humerus, and the radius.
osteoporosis is most common among
white, postmenopausal women
Bone loss begins about age
40 and by age 70 has reached 30%-50%
tend to inhibit activity of osteoclasts which maintains bone density
estrogens
short, thin, athletic women typically have
less bone mass and less adipose tissue
a source of the estrogens that inhibit bone resorption
adipose tissue
decreases blood levels of estrogens
smoking
limit the intake of calcium, proteins, and vitamins
poor diet and/or eating disorders
may increase bone loss
lack of exercise, excessive use of alcohol, use of certain medications
Recommendations for reducing the risk of osteoporosis:
adequate calcium intake on a daily basis
regular schedule of weight-bearing exercise
bis-phosphonate drugs destroy osteoclasts, which can increase bone mass by 5% to 10% and reduce fractures by up to 50%
Rickets
a childhood disorder caused by a vitamin D deficiency, so calcium and phosphorus cannot be adequately absorbed from food.
cartilage is produced, but calcification is abnormal so bones stay soft and pliable
Osteomalacia
an adult condition caused by poor nutrition, which causes bones in the spine, pelvis, and legs to become soft, deformed, and susceptible to fracture.
Osteomalacia calcium and phosphorus
calcium and phosphorus are not adequately metabolized so bones fail to calcify
Osteomalacia often occurs among
poorly nourished females who have had multiple children
Osteomyelitis
an inflammation of bone and red bone marrow, often caused by Staph aureus bacteria that infect a wound site or surgical site.
Paget’s disease
characterized by excessive and abnormal remodeling of bones, especially in the skull, pelvis, and extremities of males over 50.
Paget’s disease osteoclasts and osteoblasts
osteoclasts are overactive in bone resorption; osteoblasts are overactive in bone deposition; this causes irregular thickening and softening of these bones
Osteogenic sarcoma
the most common and deadliest form of bone cancer.
Osteogenic sarcoma Occurs
most often in femur, tibia, humerus, during growth spurt of teenage makes; may metastasize to lungs
Achondroplastic dwarfism
an autosomal dominant genetic disorder in which the long bones quit growing during childhood, even though the growth of other bones is unaffected.
Achondroplastic dwarfism chondrocytes
in the epiphyseal region fail to multiply and enlarge; individual has normal-sized head and torso, but significantly shorter limbs
Achondroplastic dwarfism can result from
a spontaneous mutation during DNA replication
The axial skeleton contains
80 bones, including the cranial bones, facial bones, bones of the middle ear, hyoid bone, bones of the vertebral column, and bones of the thorax.
The appendicular skeleton contains
126 bones, comprising the pectoral girdle and its attached upper limbs and the pelvic girdle and its attached lower limbs.
pectoral girdle contains
the scapulae and clavicles
upper limb consists of
humerus, radius, ulna, eight carpal bones, five metacarpals, fourteen phalanges
pelvic girdle consists of
two coxal bones, the sacrum, and the coccyx
each coxal bone results from
fusion of childhood ilium, ischium, and pubis
lower limb consists of
femur, patella, tibia, fibula, seven tarsal bones, five metatarsals, fourteen phalanges
Articulation or arthrosis or joint
a point of contact between two bones, or between bone and cartilage, or between bone and teeth.
Joints can be classified according to
the degree of movement that they allow.
synarthrosis
an immovable joint
amphiarthrosis
a slightly movable joint
diarthrosis
a freely movable joint
Joints can be classified on the presence or absence of
a fluid-filled synovial cavity around the bones and on the type of connective tissue that binds the bones together.
fibrous joints
have no synovial cavity and bones are held together by collagen fibers
sutures
immovable joints that bind the bones of the skull together
synostoses
Sutures fused with bone
gomphoses
immovable joints where teeth fit into their sockets
syndesmoses
slightly movable joints where two bones are held together by a ligament
cartilaginous joints
have no synovial cavity and bones are held together by cartilage
synchondroses
occur when bones are held together by hyaline cartilage (costal, rib to sternum)
symphyses
occur when bones are held together by fibrocartilage
synovial joints
have a synovial cavity filled with synovial fluid
In a synovial joint, the ends of the articulating bones are covered with
articular cartilage and held together by an articular capsule.
outer fibrous capsule consists of
dense, irregular CT; it is continuous with periosteum of each articulating bone
inner synovial membrane consists of
areolar CT; it secretes synovial fluid into joint
Synovial fluid
a viscous, pale yellow fluid consisting of hyaluronic acid and interstitial fluid that has been filtered from blood plasma.
lubricates the joint and nourishes the articular cartilage
Synovial fluid
synovial fluid contains
phagocytes that remove microbes and clean up debris resulting from normal wear and tear of joint cartilage
Many synovial joints contain
accessory ligaments that hold the bones together.
Some synovial joints contain
fibrocartilage pads, called menisci, that absorb shock and pressure to stabilize the joint.
bursa
a fluid-filled sac between muscles or where a tendon passes over a bone.
reduce friction and cushion movement at certain joints
bursae
Gliding (planar) joints
occur between small bones that have flat articular surfaces to allow movement side-to-side or back-and-forth.
example of Gliding (planar) joints
Carpals and tarsals
Hinge joints
designed so the convex surface of one bone fits into a concave surface of a second bone to allow movement in only one plane.
example of Hinge joints
Elbow or knee
Humerus and ulna
Pivot joints
occur when a rounded/pointed portion of one bone fits into a ring-like ligament associated with a second bone to allow rotation in a single plane.
example of Pivot joints
Atlas on axis
Radius and ulna
Condyloid (ellipsoidal) joints
occur when an oval condyle of one bone fits into an elliptical cavity of a second bone to allow movement side-to-side or back- and-forth in two planes.
example of Condyloid (ellipsoidal) joints
Radius and carpals meet in wrist
Between Phalanges
Saddle joints
occur between bones whose articulating surfaces have both concave and convex surfaces to allow movement side-to-side and up-and- down.
example of Saddle joints
Thumb
Ball-and-socket joints
occur when a ball-shaped head of one bone fits into a cup-like depression of a second bone to allow movement possible in any direction.
example of Ball-and-socket joints
Hip
Shoulder
Flexion
decreases the angle between the bones.
example of flexion
Elbow joint
Extension
increases the angle between the bones.
example of Extension
Hand
hyperextension
continues the extension beyond anatomical position
Abduction
moves a bone away from the midline of the body.
example of Abduction
Move arms up
Move legs out
Adduction
moves a bone toward the midline of the body.
example of Adduction
Move arms down
Move legs in
Circumduction
moves the distal end of a bone in a circle.
example of Circumduction
Rotate hand in circle. Ball and socket
Supination
rotates a forearm to place the palm in anatomical position.
Pronation
rotates forearm to turn palm away from anatomical position.
Inversion
rotates the sole of the foot inward.
Eversion
rotates the sole of the foot outward.
Dorsiflexion
bends the entire foot upward toward the shin.
Plantarflexion
bends the entire foot downward away from the shin.
Protraction
thrusts a body part forward.
Retraction
withdraws a body part to its original position.
Elevation
raises a bone vertically.
Depression
lowers a bone.
Arthritis
refers to any pain, inflammation, and/or degeneration associated with a joint.
Osteoarthritis
a progressive joint disease involving degeneration of articular cartilages, so that the articular surfaces become rough.
Osteoarthritis Usually occurs
after 40 and affects 85% of pelle older than 70, especially individuals who are overweight
Osteoarthritis is often described as
“wear- and-tear” arthritis associated with aging, because more cartilage gets destroyed than gets replaced
Osteoarthritis typically affects
joints that have been overused throughout life (hips, knees)
Gouty arthritis
results from excessive uric acid accumulation.
crystals form in joint tissue, especially great toe, causing inflammation and pain
Gouty arthritis
Rheumatoid arthritis
refers to any inflammation and thickening of the synovial membrane in a joint, followed by damage to the articular cartilage and invasion of the joint by fibrous tissue.
Rheumatoid arthritis tends to affect
women more often than men; usually occurs in middle age
a systemic autoimmune disease in which rheumatoid factor attacks a person’s own tissues as if they were infectious agents
Rheumatoid arthritis
rheumatoid factor attacks the
synovial membrane causing inflammatory cells to accumulate in synovial fluid and degrade articular cartilage
Rheumatoid arthritis cure
there is no cure for this crippling form of arthritis so treatment is aimed at reducing inflammation and slowing rate of degeneration
steroids and Rheumatoid arthritis
steroids combat inflammation and physical therapy keeps joints movable
The muscular system consists of
approximately 600 skeletal muscles, most of which are attached to the bones of the skeleton.
Makes up almost 50% of body mass
The muscular system
require integration of the muscular system with the skeletal system.
Body movements
stabilize joints and help maintain posture.
Muscle contractions
Muscles regulate
the movement of materials through hollow internal organs.
Muscle contractions generate
heat that maintains homeostasis; Generate almost 80% of body’s heat
Fascia
a sheet of fibrous connective tissue that surrounds muscles and other organs.
superficial fascia (subcutaneous layer)
separates a muscle from the skin
superficial fascia (subcutaneous layer) composition
areolar and adipose tissues
deep fascia
separates adjacent muscles from one another
deep fascia composition
dense, irregular connective tissue
Deep fascia gives rise to
three sub-layers of connective tissue. (‘Mys’ or ‘myo’ always imply muscle)
epimysium
encircles an entire muscle (deep fascia)
perimysium
surrounds fascicles comprised of bundles of muscle fibers (deep fascia)
endomysium
separates individual muscle fibers from one another in a fascicle (deep fascia)
tendon
dense connective tissue that attaches the epimysium of a muscle to the periosteum of a nearby bone. (Achilles tendon)
aponeurosis
a broad, sheet-like tendon that can attach a muscle to a bone, a muscle to another muscle, or a muscle to the skin.
origin
A muscle attachment to a stationary or relatively immovable bone
insertion
a muscle attachment to a more movable bone
belly
fleshy portion of a muscle between its points of origin and insertion
Skeletal muscles function in _________ to produce coordinated movement at a particular joint.
groups
prime mover (agonist)
the muscle that produces most of the motion (Biceps brachii inserts on radius )
synergist
a muscle that aids the movement of the prime mover by stabilizing or modifying its action (Brachialis also inserts on radius )
antagonist
a muscle that stretches and yields to the action of the prime mover ( Triceps brachii inserts on ulna )
fixators
stabilize the origin of the prime mover so that the bone doesn’t move
Excitability
the ability of a muscle to respond to a stimulus and trigger a response.
Contractility
the ability of a muscle to become shorter and thicker to generate force.
Extensibility
the ability of a muscle to stretch without damaging the tissue.
Elasticity
the ability of a muscle to return to its original shape after contracting or stretching.
muscle fibers arise from
the fusion of embryonic myoblasts
Undifferentiated myoblasts exist as________________ that assist in muscle repair
satellite cells
sarcolemma
the plasma membrane that surrounds a muscle fiber
portions of the sarcolemma penetrate into a fiber to form _____________________ to carry signals into cell
transverse (T) tubules
sarcoplasm of the fiber is filled with long protein bundles called
myofibrils
Sarcoplasm contains
glycogen to store energy and myoglobin to bind oxygen
sarcoplasmic reticulum
a network of membrane-enclosed tubules that stores calcium ions needed for muscle contractions
Myofibrils
the contractile elements of skeletal muscle and they consist of bundles of protein myofilaments.
thick filaments are composed of
approximately 300 molecules of myosin
Each myosin molecule is shaped like pair of intertwined golf clubs
each head on a myosin molecule bears an actin binding site that can form a cross-bridge; ATP binding site; ATPase enzyme
thin filaments are composed of
actin, tropomyosin, and troponin
Actin strand consists of collection globular subunits; each bears myosin-binding site where cross- bridge can attach
elastic filaments are composed of
molecules of titin
Titin molecules
help keep thick and thin filaments aligned
myosin and actin
are contractile proteins because they shorten the muscle fiber
tropomyosin and troponin
regulatory proteins because they switch contraction process on and off
sarcomere
The functional unit of a myofibril
Z discs
composed of titin molecules that anchor the thin filaments and the elastic filaments; they separate one sarcomere from another sarcomere
I band
contains only thin filaments; appears as a light region
A band
where thick and thin filaments overlap one another; appears as a dark region
H band
a region within the A band that contains only thick filaments
A skeletal muscle is
innervated by the axons of one or more motor neurons.
Skeletal muscle contractions are controlled by
nervous system
A motor unit
consists of a motor neuron, plus all the skeletal muscle fibers it innervates.
Any particular muscle fiber is innervated by _____________motor neuron
only one
A neuromuscular junction (NMJ)
a synapse between a motor neuron and a skeletal muscle fiber.
each motor neuron branches into
a cluster of axon terminals near the skeletal muscle
distal end of each axon terminal is
a swollen synaptic knob (end bulb)
sarcolemma of the muscle fiber adjacent to the synaptic knob forms
a motor end plate
motor end plate is separated from the synaptic knob by a
synaptic cleft
Each synaptic knob contains many membrane-enclosed _________________
synaptic vesicles.
Each synaptic vesicle contains
thousands of molecules of acetylcholine (Ach)
Acetylcholine receptors
located in the motor end plate where they recognize and bind molecules of acetylcholine, which begins the contraction of a single muscle fiber.
twitch
a brief contraction of all of the muscle fibers in a motor unit in response to a single stimulus from a motor neuron.
muscle fiber obeys an “all-or-nothing” law when electrically excited;
; either contracts to its maximum extent or doesn’t contract at all
The latent period
a time interval of approximately 2 milliseconds between the application of a threshold stimulus and the beginning of the twitch contraction; calcium ions that are released from the sarcoplasmic reticulum into the sarcoplasm allow cross bridges to form
force that is generated creates internal tension without shortening the muscle
The contraction period
a time interval that can last up to 100 milliseconds, during which peak muscle tension gets produced.
during this time the sliding filament mechanism is occurring
force that is generated creates external tension that is used to move a load
The relaxation period
a time interval that can last up to 100 milliseconds; during this time muscle tension decreases.
calcium ions are actively transported out of sarcoplasm back into sarcoplasmic reticulum
The strength of a twitch for a constant stimulus voltage
varies for a number of reasons, even though the electrical excitation follows the “all-or-none” law.
frequency of stimulation
Rapid delivery of nerve signals causes successive release of calcium ions, so muscle cells cannot completely relax and contraction gets stronger
concentration of calcium ions
length-tension relationship
temperature of the muscle
Warm more effective than cold
pH of the sarcoplasm
state of hydration of the muscle that affects cross bridge formation
An individual twitch
usually insufficient to do any useful work, but stronger twitches can be produced by increasing the voltage of the stimulus.
higher voltages excite more nerve fibers in the motor nerve causing more motor units to contract by recruitment (multiple motor unit summation)
Anaerobic respiration
produces ATP in the absence of oxygen, but its yield is limited and lactic acid is an end product.
Aerobic respiration
produces much more ATP, but requires plenty of oxygen.
