Ch.6 The Skeletal System: Bone Tissue Flashcards
Function of Bone Tissue
- Support (frame work, scaffolding for the soft tissue)
- Protection (surround soft tissue to prevent injury)
- Movement (act as levers for muscle to work on)
- Mineral storage (calcium, magnesium, and phosphate are deposited and withdrawn)
- Blood cell formation (all blood cells and platelets are made in red marrow cavities)
- Triglyceride storage (fats are stored in yellow marrow)
Connective tissue
- Associated with cartilage, blood, and fat
Two types of bone:
1. Spongy= 20 % of all bone, network of bone pieces with open spaces visible
2. Compact = 80% of bone smooth and solid looking
Types of Bone
- Lone Bone
- Irregular Bone
- Flat Bone
- Short Bone
Long Bone
Type of Bone
- Longer than wide
- shaft with two ends
- have a diaphysis and epiphysis
- external is compact bone, internal is spongy
- Ex: most all appendicular bones –> humerus
Irregular Bone
Type of Bone
- Complicated shapes
- if doesn’t fit other categories
- Ex: vertebra and hip bone
Flat bone
Type of Bone
- Thin, flattened and a bit curved
- thin external coat of compact bone, spongy bone inside
- Ex: Sternum, skull, ribs, shoulder blades
Short bone
Type of Bone
- cube shaped
- thin external coat of compact bone, spongy bone inside
- Ex: carpel, tarsal, talus
Long Bone anatomy
- Ends of long bone are proximal epiphysis and distal epiphysis
- Diaphysis
- Articular (hyaline)
- Epiphyseal plate
- Periosteum
- Endosteum
Diaphysis
Lone Bone Anatomy
compact bone has yellow marrow cavity inside
Epiphysis
Long Bone Anatomy
- external compact bone
- internal spongy bone
- has red marrow
Articular (hyaline) cartilage
Long Bone Anatomy
cushions bone ends
Epiphyseal plate
Long Bone Anatomy
for interstitial growth
Periosteum
Long Bone Anatomy
- covers the external surfaces
- has osteogenic cells for appositional growth
- attached to underlying bone with Sharpies fibers (collagen)
Endosteum
Long Bone Anatomy
- covers the inner surfaces
- composed of osteogenic cells
Flat Bone Anatomy
- Suture
- Outer Compact Bone
- Spongy Bone (diploe)
- Trabeculae
- Inner compact bone
Osteogenic
Cell Type
bone stem cells
Osteoblasts
Cell type
synthesize (make) new bone matrix
Osteocytes
Cell Type
- mature cells that maintain the matrix around them
- live in lacunae inside bone
Osteoclasts
Cell Type
- formed from fusion of many WBCs
- found in endosteum
- secrete enzymes that break down bone matrix from ruffled border side
Haversian systems
Compact Bone Anatomy
Made of osteons
Osteons
Compact Bone Anatomy
layers of concentric lamellae around a Haversian (central) canal
Lamellae
Compact Bone Anatomy
composed of parallel bundles of collagen fibers in calcified matrix
Lacunae
Compact Bone Anatomy
- with osteocytes living in them
- found between adjacent lamellae
Volkman (perforating) canals
Compact Bone Anatomy
connects the vessels in the periosteum and central canals
Osteocytes
Compact Bone Anatomy
- live in lacunae
- send cellular projections into the canaliculi
- The projection from one osteocyte meets the next osteocyte with gap junction between them
– Allows nutrients, wastes, chemical signals, etc to get to osteocytes
Canaliculi
Compact Bone Anatomy
small canals that connect the lacunae
Spongy Bone Anatomy
- No osteons
- Incomplete lamellae form a scaffolding of trabeculae
- Trabeculae contain lacunae and canaliculi with osteocytes
Osteogenesis
- (ossification) = formation of bone
- Begins in the early weeks (5 – 6) of embryo development
Two processes:
1. Intramembraneous ossification – flat bones
2. Endochondral ossification – all other bones esp. long bones
Interstitial Growth of the Long Bones
Resting Zone: Nearest epiphysis
1. Proliferation zone: carilage cells undergo mitosis
2. Hypertrophic zone: older cartilage cells enlarge
3. Calcification zone: matrix becomes calcified; cartilage cells die; matrix begins deteriorating
4. Ossification zone: New bone formation is occuring
Closure of the Epiphyseal Plate
- Late teens (female ~ 18, males ~ 21)
- cells in proliferating zone divide less frequently, but replacement at the diaphysis side remains constant
- Plate closes
Appositional Growth
- As bone lengthens, adjustments are made to the width to maintain the proper shape
- Osteoblasts add matrix to the external surface that develop into new osteons
- Osteoclasts widen the internal area
Bone Remodeling
- Ongoing project to replace bone
- Every week we recycle 5 to 7% of our bone mass. Spongy bone replaced every three to four years, compact bone every ten years or so.
- Purpose: renews bone tissue before deterioration sets in AND redistributes bone matrix along lines of mechanical stress.
- Osteoclasts tunnel through/remove old bone (reabsorption) and osteoblasts follow making new bone (bone deposition)
- Requires minerals (Ca2+ , PO4-, Mg2+) and vitamins (C, B12, A) and hormones (growth hormone - GH, thyroid hormone (TH), sex hormones, parathyroid hormone (PTH), and calcitonin)
Blood Calcium
Homeostasis
- HIGH blood Ca –> Calcitonin released –> stimulates calcium salt deposit in bone
- LOW blood Ca –> PTH released
Thickening of Bones
Controlled by bone cells:
- Osteoblasts (under periosteum)
– Secrete bone matrix on outer surface –> Bone becomes thicker
- Osteoclasts (in endosteum)
– Break down bone –> Medullary cavity widens
– Shaft diameter increases
Bone Fractures
- Nondisplaced
- Displaced
- Complete
- Incomplete
- Linear
- Transverse
- Compound
- Simple
Comminuted
Bone Fracture
Bone fragments into three or more pieces
- due to age
Compression
Bone Fracture
- Bone is crushed
- Ex: crushed vertebra
- osteoporotic
Spiral
Bone Fracture
- ragged break occurs when excessive twisting frces are applied to a bone
- due to sports injury
Epiphyseal
Bone Fracture
- epiphysis seperates from the diaphysis along the epiphyseal plate
Depressed
Bone Fracture
Broken bone portion is pressed inward
- typically a skull fracture
Greenstick
Bone Fracture
Bone break is incomplete
- occurs in kids
Healing of Bone Fracture
- A Hematoma forms
- Fibrocartilaginous callus forms
- Bony callus forms
- Bone remodeling occurs
Osteoporosis
- Bone reabsorption occurs faster than bone deposit = net bone loss
- Chemical composition remains the same
- Bones become light, porous and fragile particularly femur and vertebra
Osteoporosis: Risk Factors
- Genetics
- Postmenopausal or ovary removal (estrogen inhibits PTH activity)
- Lack of exercise to stress bones
- Thin/small body frame
- Poor nutrition: especially Vitamin D and calcium
- Smoking: reduces estrogen levels
Sesamoid bones
- (sesame seed shaped short bone) forms in tendons
- alter direction of pull of a tendon
