Anatomy and Physiology Exam: Chapter 6
What is rickets?
(osteomalacia of children) Results in bowed legs and other bone deformities because bones ends are enlarged and abnormally long Cause: vitamin D deficiency or insufficient dietary calcium
What are the two groups of bones?
1) Axial skeleton Long axis of body Skull, vertebral column, rib cage 2) Appendicular skeleton Bones of upper and lower limbs Girdles attaching limbs to axial skeleton
What are the functions of bone?
1. Support For body and soft organs 2. Protection Protect brain, spinal cord, and vital organs 3. Movement Levers for muscle action 4. Mineral and growth factor storage Calcium and phosphorus, and growth factors reservoir 5. Blood cell formation Hematopoiesis occurs in red marrow cavities of certain bones 6. Triglyceride (fat) storage Fat, used for an energy source, is stored in bone cavities 7. Hormone production Osteocalcin secreted by bones helps to regulate insulin secretion, glucose levels, and metabolism.
How many bones in the body?
206 named bones.
What resists compression in a long bone?
All long bones have a shaft (diaphysis), bone ends (epiphyses), and membranes Diaphysis: tubular shaft that forms long axis of bone Consists of compact bone surrounding central medullary cavity that is filled with yellow marrow in adults Epiphyses: ends of long bones that consist of compact bone externally and spongy bone internally Articular cartilage covers articular (joint) surfaces Between diaphysis and epiphysis is epiphyseal line Remnant of childhood epiphyseal plate where bone growth occurs.
Compact bone is what?
Also called lamellar bone Consists of: Osteon (Haversian system) Canals and canaliculi Interstitial and circumferential lamellae.Osteon (Haversian system) An osteon is the structural unit of compact bone Consists of an elongated cylinder that runs parallel to long axis of bone Acts as tiny weight-bearing pillars replaced every every 10 years
What is lamella?
An osteon cylinder consists of several rings of bone matrix called lamellae Lamellae contain collagen fibers that run in different directions in adjacent rings Withstands stress and resist twisting Bone salts are found between collagen fibers
What are features of the Haversian system? (via lecture)
An osteon is the structural unit of compact bone Consists of an elongated cylinder that runs parallel to long axis of bone Acts as tiny weight-bearing pillars An osteon cylinder consists of several rings of bone matrix called lamellae Lamellae contain collagen fibers that run in different directions in adjacent rings Withstands stress and resist twisting Bone salts are found between collagen fibers
Spongy bone is what?
Appears poorly organized but is actually organized along lines of stress to help bone resist any stress Trabeculae, like cables on a suspension bridge, confer strength to bone No osteons are present, but trabeculae do contain irregularly arranged lamellae and osteocytes interconnected by canaliculi Capillaries in endosteum supply nutrients replaced every every 3-4 years
What are bone salts composed of?
Bone mineral (also called inorganic bone phase, bone salt, or bone apatite) is the inorganic component of bone tissue. It gives bones their compressive strength. Bone mineral is formed from carbonated hydroxyapatite with lower crystallinity.
What is osteomalacia?
Bones are poorly mineralized Osteoid is produced, but calcium salts not adequately deposited Results in soft, weak bones Pain upon bearing weight.
What is the functional/structural unit of compact bone?
Compact bone: dense outer layer on every bone that appears smooth and solid Spongy bone: made up of a honeycomb of small, needle-like or flat pieces of bone called trabeculae Open spaces between trabeculae are filled with red or yellow bone marrow
What are the two ways cartilage can grow?
Cartilage grows in two ways: Appositional growth Cartilage-forming cells in perichondrium secrete matrix against external face of existing cartilage New matrix laid down on surface of cartilage. Interstitial growth Chondrocytes within lacunae divide and secrete new matrix, expanding cartilage from within New matrix made within cartilage.
What are some of the features associated with short bones?
Cube-shaped bones (in wrist and ankle) Sesamoid bones form within tendons (example: patella) Vary in size and number in different individuals
What are enchondral and inter membranous bone?
Endochondral ossification Bone forms by replacing hyaline cartilage Bones are called cartilage (endochondral) bones Form most of skeleton Intramembranous ossification.
Define a fracture.
Fractures are breaks During youth, most fractures result from trauma In old age, most result from weakness of bone due to bone thinning.
What resists tension in a long bone or twisting forces?
Inorganic components (cont.) Bone is half as strong as steel in resisting compression and as strong as steel in resisting tension Lasts long after death because of mineral composition Can reveal information about ancient people
What are the specific roles for the three hormones that are critical for bone metabolism? ( parathyroid hormone, vitamin D, and calcitonin)
Growth hormone: most important hormone in stimulating epiphyseal plate activity in infancy and childhood Thyroid hormone: modulates activity of growth hormone, ensuring proper proportions Testosterone (males) and estrogens (females) at puberty: promote adolescent growth spurts End growth by inducing epiphyseal plate closure Excesses or deficits of any hormones cause abnormal skeletal growth Parathyroid hormone (PTH): produced by parathyroid glands in response to low blood calcium levels Stimulates osteoclasts to resorb bone Calcium is released into blood, raising levels PTH secretion stops when homeostatic calcium levels are reached Calcitonin: produced by parafollicular cells of thyroid gland in response to high levels of blood calcium levels Effects are negligible, but at high pharmacological doses it can lower blood calcium levels temporarily
What are the different stages of bone healing?
Hematoma Torn blood vessels hemorrhage, forming mass of clotted blood called a hematoma Site is swollen, painful, and inflamed formation Fibrocartilaginous callus formation Capillaries grow into hematoma Phagocytic cells clear debris Fibroblasts secrete collagen fibers to span break and connect broken ends Fibroblasts, cartilage, and osteogenic cells begin reconstruction of bone Create cartilage matrix of repair tissue Osteoblasts form spongy bone within matrix This mass of repair tissue is called fibrocartilaginous callus Bony callus formation Within one week, new trabeculae appear in fibrocartilaginous callus Callus is converted to bony (hard) callus of spongy bone Bony callus formation continues for about 2 months until firm union forms Bone remodeling Begins during bony callus formation and continues for several months Excess material on diaphysis exterior and within medullary cavity is removed Compact bone is laid down to reconstruct shaft walls Final structure resembles original structure Responds to same mechanical stressors.
What is osteoporosis?
Imbalances between bone deposit and bone resorption underlie nearly every disease that affects the human skeleton Osteoporosis is a group of diseases in which bone resorption exceeds deposit Matrix remains normal, but bone mass declines Spongy bone of spine and neck of femur most susceptible Vertebral and hip fractures common
What is a growth plate?
Interstitial growth requires presence of epiphyseal cartilage in the epiphyseal plate Epiphyseal plate maintains constant thickness Rate of cartilage growth on one side balanced by bone replacement on other Epiphyseal plate consists of five zones: Resting (quiescent) zone Proliferation (growth) zone Hypertrophic zone Calcification zone Ossification (osteogenic) zone.
What are some of the feature of long bones?
Longer than they are wide, Limb bones. All long bones have a shaft (diaphysis), bone ends (epiphyses), and membranes Diaphysis: tubular shaft that forms long axis of bone Consists of compact bone surrounding central medullary cavity that is filled with yellow marrow in adults Epiphyses: ends of long bones that consist of compact bone externally and spongy bone internally Articular cartilage covers articular (joint) surfaces Between diaphysis and epiphysis is epiphyseal line Remnant of childhood epiphyseal plate where bone growth occurs
What is the periosteum?
Membrane that covers outside of compact bone; two types (periosteum and endosteum) Periosteum: white, double-layered membrane that covers external surfaces except joints
What are the risk factors of osteoporosis and what are some strategies to manage the potential problems?
Most often aged, postmenopausal women Affects 30% of women aged 60-70 years and 70% by age 80 30% of Caucasian women will fracture bone because of osteoporosis Estrogen plays a role in bone density, so when levels drop at menopause, women run higher risk Men are less prone due to protection by the effects of testosterone; Petite body form Insufficient exercise to stress bones Diet poor in calcium and protein Smoking Hormone-related conditions Hyperthyroidism Low blood levels of thyroid-stimulating hormone Diabetes mellitus Immobility Males with prostate cancer taking androgen-suppressing drugs Traditional treatments Calcium Vitamin D supplements Weight-bearing exercise Hormone replacement therapy Slows bone loss but does not reverse it Controversial because of increased risk of heart attack, stroke, and breast cancer
What is osteoid and hydroxyapatite?
Organic components Includes osteogenic cells, osteoblasts, osteocytes, bone-lining cells, osteoclasts, and osteoid Osteoid, which makes up one-third of organic bone matrix, is secreted by osteoblasts Consists of ground substance and collagen fibers, which contribute to high tensile strength and flexibility of bone Hydroxyapatite's (mineral salts) Makeup 65% of bone by mass Consist mainly of tiny calcium phosphate crystals in and around collagen fibers Responsible for hardness and resistance to compression
What are sacrificial bonds?
Organic components (cont.) Resilience of bone is due to sacrificial bonds in or between collagen molecules that stretch and break to dissipate energy and prevent fractures If no additional trauma, bonds re-form.
What is the volkmann's canal?
Perforating (Volkmann's) canals: canals lined with endosteum that occur at right angles to central canal Connect blood vessels and nerves of periosteum, medullary cavity, and central canal
How do you prevent osteoporosis?
Plenty of calcium in diet in early adulthood Reduce consumption of carbonated beverages and alcohol Leach minerals from bone, so decrease bone density Plenty of weight-bearing exercise Increases bone mass above normal for buffer against age-related bone loss
Fracture classification:
Position of bone ends after fracture Nondisplaced: ends retain normal position Displaced: ends are out of normal alignment Completeness of break Complete: broken all the way through Incomplete: not broken all the way through Whether skin is penetrated Open (compound): skin is penetrated Closed (simple): skin is not penetrated Can also be described by location of fracture, external appearance, and nature of break
Where does new bone form after a fracture?
Position of bone ends after fracture Nondisplaced: ends retain normal position Displaced: ends are out of normal alignment Completeness of break Complete: broken all the way through Incomplete: not broken all the way through Whether skin is penetrated Open (compound): skin is penetrated Closed (simple): skin is not penetrated Can also be described by location of fracture, external appearance, and nature of break
How does red and yellow bone marrow differ?
Red marrow is found within trabecular cavities of spongy bone and diploë of flat bones, such as sternum In newborns, medullary cavities and all spongy bone contain red marrow In adults, red marrow is located in heads of femur and humerus, but most active areas of hematopoiesis are flat bone diploë and some irregular bones (such as the hip bone) Yellow marrow can convert to red, if person becomes anemic
What are some of the features of cancellous to cortical bone?
There are two types of bone tissue: cortical bone and cancellous bone: The tissues are biologically identical; the difference is in how the microstructure is arranged. ... As its name implies, cortical bone forms the cortex, or outer shell, of most bones. Cortical (compact) bone is much denser than cancellous bone.
What are some of the features associated with flat bones?
Thin, flat, slightly curved Sternum, scapulae, ribs, most skull bones
What are the different types of cartilage?
Three types of cartilage: Hyaline cartilage Provides support, flexibility, and resilience Most abundant type; contains collagen fibers only Articular (joints), costal (ribs), respiratory (larynx), nasal cartilage (nose tip) Elastic cartilage Similar to hyaline cartilage, but contains elastic fibers External ear and epiglottis Fibrocartilage Thick collagen fibers: has great tensile strength Menisci of knee; vertebral discs.
What is wolfs law and how does bone react to the forces that are upon it?
Wolf's law states that bones grow or remodel in response to demands placed on them Stress is usually off center, so bones tend to bend Bending compresses one side, stretches other side Diaphysis is thickest where bending stresses are greatest Bone can be hollow because compression and tension cancel each other out in center of bone. Handedness (right- or left-handed) results in thicker and stronger bone of the corresponding upper limb Curved bones are thickest where most likely to buckle Trabeculae form trusses along lines of stress Large, bony projections occur where heavy, active muscles attach Weight lifters have enormous thickenings at muscle attachment sites of most used muscles Bones of fetus and bedridden people are featureless because of lack of stress on bones
What is the endosteum?
covers inside portion of compact bone; Delicate connective tissue membrane covering internal bone surface Covers trabeculae of spongy bone Lines canals that pass through compact bone Like periosteum, contains osteogenic cells that can differentiate into other bone cells
What is the medullary canal?
is the central cavity of bone shafts where red bone marrow and/or yellow bone marrow (adipose tissue) is stored; hence, the medullary cavity is also known as the marrow cavity.
What are lacunae?
small cavities that contain osteocyte Osteocytes: Mature bone cells in lacunae that no longer divide Maintain bone matrix and act as stress or strain sensors Respond to mechanical stimuli such as increased force on bone or weightlessness Communicate information to osteoblasts and osteoclasts (cells that destroy bone) so bone remodeling can occur
