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Audrina Osoy Period 01 Skeletal system - Coggle Diagram
Audrina Osoy Period 01 Skeletal system
Microscopic anatomy of bone tissue
Cells of bone tissue
Osteogenic cells(or osteoprogenitor cells)
Mitotically active stem cells in periosteum and endosteum
When stimulated, they differentiate into osteoblasts or bone-lining cells
Some remain as osteogenic stem cells
Osteoblasts
Osteoid is made up of collagen and calcium-binding proteins. Collagen makes up 90% of bone protein
Osteoblasts are actively mitotic
Bone-forming cells that secrete unmineralized bone matrix called osteoid
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 weight
Communicate information to osteoblasts and osteoclasts (cells that destroy bone) so bone remodeling can occur
Bone-lining cells
Flat cells on bone surfaces believed to also help maintain matrix (along with osteocytes)
Osteoclasts
When active, cells are located in depressions called resorption bays
Cells have ruffled borders that serve to increase surface area for enzyme degradation of bone
Giant, multinucleate cells function in bone resorption (breakdown of bone)
Also helps seal off area from surrounding matrix
Derived from same hematopoietic stem cells that become macrophages
Chemical composition of the bone
Organic components
:Includes osteogenic cells, osteoblasts, osteocytes, bone-lining cells, osteoclasts, and osteoid
Osteoid (one-third of organic bone matrix) consists of ground substance and collagen fibers contributing to high tensile strength and flexibility
Resilience is due to sacrificial bonds in/between collagen molecules that stretch and break to dissipate energy and re-form if no additional trauma occurs
inorganic components
:Hydroxyapatites (mineral salts) make up 65% of bone by mass
Consist mainly of tiny calcium phosphate crystals in and around collagen fibers
Responsible for hardness and resistance to compression
Compact bone(lamellar bone) consist of:
Canals and canaliculi
Lacunae: small cavities that contain osteocytes
Canaliculi: hairlike canals that connect lacunae to each other and to central canal
Perforating (Volkmann's) canals: lined with endosteum; occur at right angles to central canal to connect blood vessels and nerves of periosteum, medullary cavity, and central canal
Osteoblasts maintain contact with each other and osteocytes via cell projections with gap junctions; when matrix hardens, canaliculi form to allow communication and nutrient/waste relay
Central (Haversian) canal: runs through core of osteon; contains blood vessels and nerve fibers
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
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
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
Appears poorly organized but is actually organized along lines of stress to help
bone resist any stress
Capillaries in endosteum supply nutrients
Bone fracture repair
During youth, most fractures result from trauma
In old age, most result from weakness of bone due to bone thinning
Fractures are breaks
Three “either/or” fracture classifications
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
Treatment involves reduction, the realignment of broken bone ends
Closed reduction: physician manipulates to correct position
Open reduction: surgical pins or wires secure ends
Immobilization of bone by cast or traction is needed for healing
Time needed for repair depends on break severity, bone broken, and age
of patient
Repair involves four major stages
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
Osteoblasts form spongy bone within matrix
Create cartilage matrix of repair tissue
Bony callus formation
Callus is converted to bony (hard) callus of spongy bone
Bony callus formation continues for about 2 months until firm union forms
Within one week, new trabeculae appear in fibrocartilaginous callus
Hematoma formation
Torn blood vessels hemorrhage, forming mass of clotted blood called a hematoma
Site is swollen, painful, and inflamed
Bone remodeling
Compact bone is laid down to reconstruct shaft walls
Final structure resembles original structure
Excess material on diaphysis exterior and within medullary cavity is removed
Responds to same mechanical stressors
Begins during bony callus formation and continues for several months
Differences between male and female skeleton
Male
Skull & Structure: Thicker and heavier bones with stronger muscle attachments, a squarer to sharp jaw, and larger brow.
Pelvis: Narrower, deeper, and heavier with a smaller, short distanced opening.
Female
Pelvis: Broader, wider, and lighter with a larger opening to allow for childbirth.
Skull: Smoother and lighter bones with a softer jawline and smaller brow.
Names of all the bones
Axial skeleton
Long axis of body
Skull, vertebral column, rib cage
Skull (Cranium / skull, Cranial bones,etc)
Vertebral Column (Vertebrae / spine,etc)
Rib Cage (Sternum , Ribs,etc)
Appendicular skeleton
Bones of upper and lower limbs
Girdles attaching limbs to axial skeleton
Clavicle (collarbone), Scapula (shoulder blade)
Humerus (upper arm), Radius & Ulna (forearm), Carpals (wrist), Metacarpals (hand), Phalanges (fingers)
Pelvic Girdle: Coxal/Hip bones
Lower Limbs: Femur (thigh), Patella (kneecap), Tibia (shin bone), Fibula (calf bone), Tarsals (ankle), Metatarsals (foot), Phalanges (toes)
Anatomy of the long bone
Gross anatomy
:All long bones have a shaft (diaphysis), bone ends (epiphyses), and membranes
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
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
Membranes: two types (periosteum and endosteum)
Periosteum
: white, double-layered membrane that covers external surfaces except joints
Fibrous layer: outer layer consisting of dense irregular connective tissue consisting of Sharpey's fibers that secure to bone matrix
Osteogenic layer: inner layer abutting bone and contains primitive osteogenic stem cells that gives rise to most all bone cells
Contains many nerve fibers and blood vessels that continue on to the shaft through nutrient foramen openings
Anchoring points for tendons and ligaments
Endosteum
Lines canals that pass through compact bone
Covers trabeculae of spongy bone
Delicate connective tissue membrane covering internal bone surface
Like periosteum, contains osteogenic cells that can differentiate into other bone cells
Hematopoietic tissue in bones
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
Bone remodeling
Dig depressions or grooves as they break down matrix
Secrete lysosomal enzymes and protons (H+) that digest matrix
Resorption is function of osteoclasts
Remodeling units: packets of adjacent osteoblasts and osteoclasts coordinate remodeling process
Occurs at surfaces of both periosteum and endosteum
Acidity converts calcium salts to soluble forms
Bone remodeling consists of both bone deposit and bone resorption
Osteoclasts also phagocytize demineralized matrix and dead osteocytes
Bone Deposit: New bone matrix is deposited by osteoblasts
Joints
Bones joined by dense fibrous connective tissue
Two classifications:
Structural: three types based on what material binds the joints and whether a cavity is present
Fibrous
Cartilaginous
Synovial
Functional classifications: three types based on movement joint allows
Synarthroses: immovable joints
Amphiarthroses: slightly movable joints
Synarthroses: immovable joints
No joint cavity
Functions of joints: give skeleton mobility and hold skeleton together
Most are immovable
Depends on length of connective tissue fibers
Joints, also called articulations: sites where two or more bones meet
Fibrous joints
syndesmoses
Bones connected by ligaments, bands of fibrous tissue. Short fibers offer little to no movement (Example: inferior tibiofibular joint). Longer fibers offer a larger amount of movement (Example: interosseous membrane connecting radius and ulna)
gomphoses
Peg-in-socket joints. Only examples are the teeth in alveolar sockets. Fibrous connection is the periodontal ligament.
sutures
igid, interlocking joints of skull. Closed, immovable sutures referred to as synostoses. (Found only in the skull)
Bones united by cartilage
Not highly movable
Two types
Symphyses
Hyaline cartilage also present as articular cartilage on bony surfaces
Fibrocartilage unites bone in symphysis joint
Example:
Pubic symphysis
Intervertebral joints
Symphyses are strong, amphiarthrotic (slightly movable) joints
Synchondroses
Bar or plate of hyaline cartilage unites bones
Almost all are synarthrotic (immovable)
Example:
Become synostoses after plate closure
Cartilage of 1st rib with manubrium of sternum
Temporary epiphyseal plate joints
Like fibrous joints, have no joint cavity
Synovial Joints
All are diarthrotic (freely movable)
Include almost all limb joints
Bones separated by fluid-filled joint cavity
Six types based on shape of articular surface and movement:
Pivot
Condylar
Hinge
Saddle
Plane
Ball-and-socket
Movements allowed by Synovial Joints
Plane joint
Movement: Nonaxial movement (Gliding)
Examples: Intercarpal joints, intertarsal joints, joints between vertebral articular surfaces
Hinge joint
Movement: Uniaxial movement (Flexion and extension) Examples: Elbow joints, interphalangeal joints
condylar joint
Movement: Biaxial movement (Flexion and extension, Adduction and abduction) Examples: Metacarpophalangeal (knuckle) joints, wrist joints
Pivot joint
Movement: Uniaxial movement (Rotation)
Examples: Proximal radioulnar joints, atlantoaxial joint
Saddle joint
Movement: Biaxial movement (Adduction and abduction, Flexion and extension)
Example: Carpometacarpal joints of the thumbs
Ball-and-socket joint
Movement: Multiaxial movement (Flexion and extension, Adduction and abduction, Rotation)
Examples: Shoulder joints and hip joints
Disorders/diseases
Imbalances between bone deposit and bone resorption underlie nearly every disease that affects the human skeleton
Three major bone diseases
Osteoporosis:a group of diseases in which bone resorption exceeds deposit
Vertebral and hip fractures common
Spongy bone of spine and neck of femur most susceptible
Matrix remains normal, but bone mass declines
Risk factors
Affects 30% of women aged 60–70 years and 70% by age 80
Estrogen plays a role in bone density, so when levels drop at menopause, women run higher risk
Most often aged, postmenopausal women
Men are less prone due to protection by the effects of testosterone
Insufficient exercise to stress bones
Diet poor in calcium and protein
Smoking
Genetics
Hormone-related conditions
Hyperthyroidism
Diabetes mellitus
Consumption of alcohol or certain medications
Treatments
Hormone replacement therapy
Controversial because of increased risk of heart attack, stroke,
and breast cancer
Slows bone loss but does not reverse it
Weight-bearing exercise
Vitamin D supplements
Calcium
Bisphosphonates:: decrease osteoclast activity and number
Partially reverse osteoporosis in spine
Denosumab
Monoclonal antibody shown to reduce fractures in men with prostate
cancer
Improves bone density in elderly
Prevent
Paget’s disease
Usually occurs in spine, pelvis, femur, and skull
Rarely occurs before age 40
Very high ratio of spongy to compact bone and reduced mineralization
Cause unknown: possibly viral
Called Pagetic bone
Treatment includes calcitonin and bisphosphonates
Excessive and haphazard bone deposit and resorption cause bone to grow fast
and develop poorly
Osteomalacia
Bones are poorly mineralized
Osteoid is produced, but calcium salts not adequately deposited
Results in soft, weak bones
Pain upon bearing weight
Rickets (osteomalacia of children)
Cause: vitamin D deficiency or insufficient dietary calcium
Results in bowed legs and other bone deformities because bones ends are enlarged and abnormally long
Types of bones
Long bones
Limb bones (longer than they are wide)
Short bones: Wrist and ankle bones
(cube-shaped); includes Sesamoid bones like the patella
Flat bones
Sternum, scapulae, ribs, most skull bones (thin, flat, slightly curved)
Irregular bones
Vertebrae and hip bones (complicated shapes)