BIO-151 (Exam 3) Study Guide
Bone Growth in Thickness
1. Bone forms at surface in ridges on either side of periosteal blood vessels • Osteoblasts secrete ECM, become surrounded osteocytes 2. Ridges around blood vessels form tunnels • Periosteum is now endosteum inside bone 3. Osteoblasts in endosteum secrete ECM, form new rings of concentric lamellae
Ossification
1. Initial formation of bones in embryo and fetus 2. Growth of bones during infancy, childhood and adolescence 3. Remodeling of bone 4. Repair of fractures
Muscular Tissue Function
1. Movement: through interaction of skeletal muscles, bones, & joints 2. Posture: stabilize body positions 3. Storage and movement
Bone Remodeling
Bone continuously renews itself throughout life • Includes about 5% of the total bone mass at a time • Bone mass can be increased in response to heavy loads or strain • Allows for extraction of bone minerals to maintain calcium levels in blood • New bone is more fracture resistant than old bone
Enlargement of the Medullary Cavity
Bone tissue lining medullary cavity is destroyed by osteoclasts in the endosteum
Cardiac Muscle
Branched, striated fibers Usually only one nucleus in center of cell
hydroxyapatite crystals
Calcium phosphate + calculate hydroxide
Growth of cartilage model
Chondroblasts----->chondrocytes • Chondrocytes divide and secrete cartilage ECM ▪Interstitial growth (growth in length) • Cartilage in middle begins to calcify• Chondrocytes within calcified ECM begin dying
Periosteum
Connective tissue sheath & associated blood supply. Protection, repair, nourishment, attachment for ligaments & tendons
Structure of Skeletal Muscle Tissue
Connective tissue surrounding muscle fibers In hypodermis, areolar connective and adipose tissue separate skin from muscle Blood vessels Nerves
Histology of Bone
Connective tissue: few cells, much extracellular matrix (ECM). ECM: 15% water, 30% collagen, 55% mineral salts. Also calcium carbonate, magnesium, fluoride, potassium, sodium
Myofibrils
Contractile organelles is skeletal muscle fibers appear as thread-like structures within sarcoplasm (diameter about 2 μm) Extend the entire length of a muscle fiber Striation in myofibrils is source of muscle fiber striation
A band
Darker middle part of sarcomere ▪ Extends entire length of thick filaments
Bone remodeling phase
Dead portions of fracture resorbed by osteoclasts Compact bone replaces spongy bone where needed Osteoclasts remodel bone to original shape
Terminal cisterns
Dilated end sacs found on both sides of a T tubule
Nerve and Blood Supply
Each skeletal muscle penetrated by a nerve, an artery, & 1 - 2 veins ▪ Nerves are somatic motor neurons ▪ Thin axon extends from brain or spinal cord to group of muscle fibers Each muscle fiber is close to 1+ blood capillaries ▪ Active muscle fibers require oxygen, glucose, fatty acids ▪ Blood removes heat and metabolic waste products
Myofilaments
Even smaller filaments within myofibrils Muscle contraction occurs as filaments slide past each other Do not extend length of myofibril▪ Smaller compartments of myofilaments: sarcomeres ▪ Z discs: dense protein separating sarcomeres
Sarcoplasmic reticulum
Fluid-filled membranous sacs surrounding each myofibril Stores Ca2+ in a resting muscle fiber Release of Ca2+ triggers muscle contraction
Factors Affecting Bone Growth and Remodeling
Hormones • Include Insulin-like growth factor (IGF), Thyroid hormones (T3, T4), insulin • Promote cell division, stimulate osteoblasts, enhances bone protein synthesis • Increase of sex hormones (estrogen, androgens) at puberty trigger growth and skeletal changes
Formation of articular cartilage and epiphyseal growth plate
Hyaline cartilage covering epiphyses becomes articular cartilage Epiphyseal (growth) plate: Hyaline cartilage remaining between diaphysis and epiphysis until maturity
Skeletal Muscle
Long, cylindrical fibers with striation (stripes) Multinucleated with nuclei at periphery of cell Voluntary movement controlled by neurons of somatic nervous system Some unconscious control (diaphragm in breathing, posture) Heat production Protection
Myosin
Main component of thick filaments Motor protein in all three types of muscle tissue Converts ATP chemical energy into mechanical energy
Actin
Main component of thin filaments. Actin molecules twist together to form helix-shaped filament Myosin binding sites to bind myosin heads
Exercise and Bone Tissue
Main strain on bone is pull of skeletal muscles and gravity Mechanical strain causes increase deposition of minerals and collagen fibers Athletes have thicker and stronger bones
Smooth muscle
Non-striated spindle-shaped cells with single central nucleus Gap junctions common Motion (usually involuntary), some autorhythmicity to cells of digestive tract
Bone deposition
Osteoblasts add minerals & collagen fibers
Bone resorption
Osteoclasts remove bone minerals & collagen fibers
Compact bone
Osteon: repeating unit within bone • Osteonic (haversian, central) canal: runs through center of osteon ▪ contains blood vessels, lymphatic vessels, nerves • Concentric lamellae: concentric rings in the osteon • Bone lacunae: ("little lakes"): contain osteocytes • Interstitial lamellae: spaces between the osteons
Aging and Bone Tissue
Over time, resorption by osteoclasts outpaces deposition by osteoblasts • Loss of bone mass from demineralization Especially significant to aging in women • Brittleness from decreased protein synthesis with age
Regulation of Blood Calcium Levels
Parathyroid hormone (PTH): increases blood Ca2+ level • Negative feedback system with parathyroid cells acting as receptors • Low blood Ca2+ triggers PTH secretion▪Increases the number and activity of osteoclasts▪Increases Ca2+ reabsorption in the kidney ▪Stimulates formation of calcitriol (active form of Vitamin D), promoting Ca2+ absorption from gastrointestinal tract
Z Disc
Passes through the center of the I band
Sarcolemma
Plasma membrane of muscle fibers Nuclei are located next to sarcolemma
Myosin tail
Points toward the M line in center of sarcomere
Development of medullary cavity
Primary ossification center grows toward the ends Osteoclasts break down some trabeculae, creating medullary cavity Wall of cavity eventually replaced by compact bone
Sphincters
Rings of smooth muscles at exit of hollow organs Cardiac muscle contractions Smooth muscles contract & relax in walls of blood vessels, gastrointestinal tract, gall bladder, reproductive system, & urinary system
Vertebral compression fracture
vertebral body compressed into wedge shape
Zone of overlap
where thick and thin filaments overlap
Periosteal arteries/veins
with nerves enter diaphysis through perforating canals
Bone's Role in Calcium Homeostasis
• 99% of body calcium is stored in bone• Blood level calcium ions (Ca2+) are very closely regulated • Nerve & muscle cells depend on stable Ca2+ level in extracellular fluid • Blood clotting and many enzyme activities require Ca2+ • Osteoblasts and osteoclasts help "buffer" the blood Ca2+ level by bone remodeling
Reparative phase: fibrous cartilage callus formation
• Blood vessels grow into fracture hematoma • Fibroblasts from periosteum enter the fracture s produce collagen fibers • Cells from periosteum develop into chondroblasts and produce fibrous cartilage • Formation of fibrous cartilage (collagen fibers & cartilage)
Osteoblasts
• Bone deposition: synthesize & secrete components of ECM including collagen • Initiate calcification • Differentiate into osteocytes
Intramembranous ossification
• Bone develops directly within mesenchyme mesenchyme = embryonic connective tissue ▪ flat bones of skull, facial bones, mandible, medial part of clavicle
Formation of trabeculae
• Connective tissue differentiates into red bone marrow
Osteoclasts
• Derived from the fusion of monocytes • Ruffled border on bone-surface side • Bone resorption: Releases lysosomal enzymes and acids onto bone • Concentrated in endosteum
Microscopic Anatomy of Skeletal Muscle
• Diameter: 10 to 100 μm • Length: average 10 cm (4 inches) • Multinucleated due to fusion of myoblasts during development • Mature muscle fibers (myocytes) do not undergo cell division Number of muscle fibers is set before birth
Epimysium (outer layer)
• Encircles entire muscle • Dense irregular connective tissue
Reactive phase
• Formation of fracture hematoma • Swelling and inflammation • Blood supply is cut off, nearby bone cells die • Phagocytes and osteoclasts remove the dead bone tissue
Endochondral ossification
• Hyaline cartilage develops from mesenchyme, then replaced by bone
Development of primary ossification center
• Inward from surface • Artery penetrates the perichondrium and cartilage model ▪Stimulates osteoprogenitor cells in perichondrium---->osteoblasts ▪ Perichondrium----->periosteum
Spongy bone
• Located in epiphyses of long bones & the interior of short, flat, sesamoid, and irregular bones • Always found within outer layer of compact bone
Osteocytes
• Mature bone cells • Main cells of bone tissue • Carry out bone metabolism
Development of periosteum
• Mesenchyme at edge of bone develops into periosteum • Thin layer of compact bone replaces spongy bone at surface
Osteoprogenitor cells
• Only bone cell that divides • Differentiate into osteoblasts • Found in inner osteogenic layer of periosteum, in endosteum, & in canals within bone that have blood vessels
Reparative phase: bony callus formation
• Osteoprogenitor cells develop into osteoblasts. • Osteoblasts produce trabeculae • Fibrous cartilage callus is converted into spongy bone bony callus
Endomysium (inner layer)
• Separates individual muscle fibers • Mostly reticular fibers
articular cartilage
Thin layer of hyaline cartilage covering the articulation part of epiphysis. Lacks perichondrium and blood vessels. Reduces friction and absorbs shock
Contractility
ability to contract when stimulated by nerve impulse
Electrical Excitability
ability to produce muscle action potentials (impulses) in response to specific stimuli Chemical stimuli (neurotransmitters, hormones, pH) Autorhythmic response to electrical signals
Elasticity
ability to return to original shape after contraction or extension
Extensibility
ability to stretch within limits without being damaged
Thin filaments
actin protein
Zone of resting cartilage
anchors epiphyseal plate to epiphysis
Muscle fibers
are also called myocyte cells
H Band
area within A band with only thick filaments
Intercalated discs
attach muscle cells together contain gap junctions and desmosomes
Metaphyses
between diaphysis and epiphyses
Myosin head
binds ATP and actin ATP binding site hydrolyzes ATP to generate energy
Myoglobin
binds O2 that diffuses into muscle fiber -found only in muscle -releases O2 when needed
Epiphyseal line
bone has replaced cartilage in epiphyseal plate, bone ceases growth
Comminuted fracture
bone is splintered, crushed, or broken in pieces at the site of impact
Open (Compound) fracture
broken ends of the bone protrude through skin
Vitamin D
calcium absorption in the intestines
Inner osteogenic layer
cell layer enables bone growth
Zone of proliferating cartilage
chondrocytes divide and secrete ECM
Vitamin C
collagen synthesis
interosteonic canals
connect blood vessels/ nerves in medullary cavity, periosteum, & osteonic canals
Calcification
crystallization of mineral salts hardens bone. Initiated by osteoblasts Osteoblasts---->osteocytes Osteoblast deposits calcium into ECM
Sarcoplasm
cytoplasm of muscle fibers -lots of glycogen
Calcitonin
decreases blood Ca2+ level • Produced in thyroid gland • High blood Ca2+ levels trigger CT secretion▪Inhibits activity of osteoclasts▪Speeds uptake and deposition into bone
Outer fibrous layer
dense irregular connective tissue
Fascia
dense sheet of irregular connective tissue Lines body wall and limbs Supports and surrounds muscles and organs Holds muscles with similar functions together Carries nerves, blood vessels, and lymphatic vessels
Closed (Simple) fracture
does not break the skin
Nutrient artery/vein
enter diaphysis of long bones through nutrient foramen ▪ Supply inner compact bone, spongy bone, and bone marrow
Bone Trabeculae
flat plates with network of thin, bony columns, lined with endosteum • No osteons • Have lamellae, bone lacunae, osteocytes, bone canaliculi • Spaces filled with red or yellow marrow, blood vessels
Pott
fracture of distal end of fibula
Colles
fracture of radius where the distal fragment is displaced posteriorly
Thermogenesis
generation of heat
Periosteal capillaries
grow into the calcified cartilage ▪Induces growth of primary ossification center in center of bone ▪Trabeculae form in the calcified cartilage
Appositional growth
growth at outer surface of tissue Cells in inner cellular layer of the perichondrium differentiate into chondroblasts, chondroblasts surrounded with extracellular matrix & become chondrocytes Matrix accumulates beneath the perichondrium on outer surface of cartilage Continues through adolescence
Interstitial growth
growth within the tissue Division of existing chondrocytes & deposition of increasing amounts of extracellular matrix Childhood and adolescence
Troponin
holds tropomyosin in place
Medullary Cavity
hollow space within diaphysis. Contains fatty yellow bone marrow and blood vessels
Titan
huge, elastic protein stabilizes thick filament from Z disc to M line
epiphyseal growth plate
hyaline cartilage allows diaphysis to grow in length
Tropomyosin
in relaxed muscle, blocks myosin from binding to actin
autorhythmicity
involuntary alternating contraction and relaxation Blood pumping to body adjusted by hormones & autonomic (involuntary) nervous system
Minerals
large amounts needed, especially calcium and phosphorus
Zone of hypertrophic cartilage
large maturing chondrocytes
Dystrophin
links thin filaments to integral membrane proteins of sarcolemma
Glycogen
macromolecule made of glucose -glucose is used in ATP synthesis
Thick filaments
myosin protein
Impacted fracture
one end of bone firmly driven into interior of other end
Greenstick fracture
one side of bone is fractured, other side bends
Mitochondria
produce ATP to provide energy for muscle fibers
Hemopoiesis
produce blood cells and platelets in red bone marrow
Epiphyses
proximal and distal ends of the bone
Zone of calcified cartilage
replacement by bone in progress
Vitamin A
stimulates osteoblasts
Mineral Homeostasis
store and release minerals
Triglyceride storage
stored in adipocytes in yellow bone marrow
Metaphyseal artery/vein
supplies the metaphyses
epiphyseal artery/vein
supply the epiphyses
Vitamins K, B12
synthesis of bone proteins
Perforating fibers
thick bundles of collagen extend from periosteum into bone extracellular matrix. attaches collagen to bone
Bone canaliculi
thin channels connect bone lacunae ▪ allow nutrients to diffuse to osteocytes ▪ osteocytes extend processes through canaliculi & communicate with each other via gap junctions
I Band
thin filaments only
Endosteum
thin membrane lining medullary cavity. Contains bone‐forming osteoprogenitor cells and connective tissue
T tubules
Tunnels of sarcolemma toward center of muscle fibers -Filled with interstitial fluid -Allows fast spread of action potential across sarcolemma
Development of secondary ossification centers
Usually around time of birth Arteries entering the epiphyses stimulate formation Spongy bone in center of epiphyses ▪ No medullary cavity in epiphyses Outward from center to surface
Diaphysis
Shaft (body)
Function of Bones
Skeletal framework: support soft tissues, attachment sites for tendons. Protection of internal organs. Work with muscles to produce movement
M Line
Supporting proteins hold thick filaments together at the center of the H band
Perimysium (middle layer)
Surrounds muscle fascicles (bundles of 10 - 100+ muscle fibers) Dense irregular connective tissue