Bones and Joints - Lecture Exam 2 Flashcards
What are the tissues and organs that compose of the skeletal system?
- Osseous tissue is a connective tissue with a matrix hardened by calcium phosphate and other minerals
- Mineralization/calcification is the hardening process of bones
- Bones is an organ composed of bone tissue, bone marrow, cartilage, adipose tissue, nervous tissue, and fibrous connective tissue
Describe the general features of a long bone
- A long bone is the bones of appendages, longer than wide, rigid levers, and crucial for movement
- Articular cartilage, made up of hyaline cartilage, is at the ends of bones
- Epiphysis are the ends of the long bone; Diaphysis is the shaft of a long bone
- periosteum is the outermost membrane of the bone, endosteum is the inner membrane of the bone also known as the lining of the bone marrow cavity
- Medullary cavity: the hollow region of the diaphysis where red or yellow bone marrow is found
- Epiphyseal plate/growth plate: area of hyaline cartilage that separates epiphyses and diaphyses of children’s bones, enables growth in length
- Nutrient foramina: minute holes in bone surface that allows blood vessels to penetrate
Compact bone vs Spongy bone
Compact bone: dense outer shell of bone
Spongy (cancellous) bone: loosely organized bone tissue. Found in center of ends and center of shafts of long bones and in middle of nearly all others. Covered by more durable compact bone
Periosteum vs. Endosteum
Periosteum—external sheath covering most of bone
– Outer fibrous layer of collagen. Some fibers continuous with tendons
• Perforating fibers: penetrate into bone matrix
– Inner osteogenic layer of bone-forming cells
• Important to bone growth and healing of fractures
Endosteum—thin layer of reticular connective tissue lining marrow cavity
– Has cells that dissolve osseous tissue and others that deposit it
What are the shapes of bone?
Flat bones: cranium
- Thin, curved plates
- Protect soft organs
Long bones: bones of the appendages
- Longer than wide
- Rigid levers acted upon by muscles; crucial for movement
Short bones: wrists and ankles
- Approximately equal in length and width
- Glide across one another in multiple directions
Irregular bones: vertebrae, some face/cranial bones
-Elaborate shapes that do not fit into other categories
What are the functions of the skeletal system?
• Support—limb bones and vertebrae support body; jaw bones
support teeth; some bones support viscera
• Protection—of brain, spinal cord, heart, lungs, and more
• Movement—limb movements, breathing, and other
movements depend on bone
• Electrolyte balance—calcium and phosphate levels
• Acid–base balance—buffers blood against large pH changes
by altering phosphate and carbonate salt levels
• Blood formation—red bone marrow is the chief producer of
blood cells
Osteogenic Cells
stem cells in endosteum and inner layer of periosteum. They arise from embryonic mesenchyme, and multiply continuously to give rise to most bone cell types
Osteoblasts
- bone forming cells
- single layer of cells under endosteum and periosteum
- nonmitotic
- synthesize soft organic matter of matrix which hardens by mineral deposition
Osteocytes
- former osteoblasts that are trapped in the matrix they deposited
- contains strain sensors that produce biochemical signals that regulate bone remodeling when stressed (shape and density changes that are adaptive)
- also gap junctions that are a passage of nutrients, waste and signals
Osteoclasts
- bone dissolving cells found on bone surface
- develops from same bone marrow stem cells that produce blood cells, not the same as other bone cells
- fusion of several stem cells forms large cells with multiple nuclei in each cell with a ruffled border
The matrix of bone tissue
Organic matter: synthesized by osteoblasts, provides flexibility with collagen fibers.
-Contains collagen, carb-protein complexes like proteoglycans, glycoproteins, and glycosaminoglycans
Inorganis matter: provides structure
- 85% hydroxyapatite
- 10% calcium carbonate
- other minerals: fluoride, sodium, potassium and magnesium
State the importance of each constituent of bone tissue
- osteons (haversian systems)
- central canal
- concentric lamellae surround a central canal running longitudinally
- preforating canal: transverse or diagonal passages
- circumferential lamellae fill outer region of dense bone
- interstitial lamellae: fill irregular regions between osteons
- lacunae: tiny cavities where osteons reside
- canaliculli: litttle channels that connect lacunae
Distinguish between the two typesof marrow
Bone Marrow: soft tissue occupying marrow cavities of long bones and small spaces of spongy bone
Red Bone Marrow: (myeloid tissue) contains hemopoietic tissue that produces red blood cells.
- Every bone in a child.
- In adults, red bone marrow is found in skull, vertebrae, ribs, sternum, part of pelvic girdle, and proximal heads of femur/humerus
Yellow Bone Marrow: found only in adults.
- fatty marrow that does not produce blood
- may transform back to red marrow in the event of chronic anemia
Compare the histology of the two types of bone tissue
Spongy bone:
-few osteons with no central canal, osteocytes close to bone marrow
-lattice of bone covered with endosteum
>slivers of bone:spicule, thin bone plates trabeculae
-spaces filled with red bone marrow
-provides strength with minimal weight
Compact bone:
-contains osteons, haversian systems.
Describe intramembranous ossification (inside membrane)
- in a membrane, mesenchyme cells gather, differentiate into osteogenic cells
- Osteogenic cells divide into osteoblasts.
- osteoblasts gather at the borders of blood vessels - osteoblasts secrete osteoid, collagen fibers appear, Ca3(PO4)2 calcium phosphate hardens/calcifies the osteoid surroundings
-Produces flat bones of skull and clavicle in fetus, thickens long bones throughout life.
Describe endochondral ossification (in the cartilage of fetus)
-The hyaline cartilage model
1. Chondrocytes enlarge (hypertrophy) and explode, cartilage matrix crystalizes
2. Mesenchyme cells gather around crystallized matrix
(Mesenchyme cells divide into osteogenic cells and osteoblasts).
3. osteoblasts: secrete osteoid, collagen fibers appear, calcium phosphate crystals appear
Notes:
- happens at the center of the model, creates diaphysis, bone collar forms around outside as well.
- creates bones in epiphyses after
- growth plate of hyaline cartilage remains between developing diaphysis and epiphysis until puberty
Explain how bones elongate
*epiphyseal plate: cartilage transitions into bones
- a growth zone where bone elongates and contains hyaline in the middle with transition zones on each side where cartilage is replaced by bone
- bone elongation: result of cartilage growth within epiphyseal plate (interstitial)
- when cartilage is gone, epiphyses close.
- epiphyseal line of spongy bone marks former epuphyseal plate
- lengthwise growth is finished, occurs at different ages in different bones.
Explain how bones widen and thicken
*Appositional growth - occurs at bone surface
- continual growth in diameter and thickness
- intremembraneous ossification
- osteoblasts of inner periosteum deposit osteoid tissue, which becomes trapped as tissues calcifies
- lays down in matrix in layers parallel to surface, forms circumferential lamellae, and osteoclasts of endosteum enlarge marrow cavity
Bone remodeling
- bone absorption and deposition occurs throughout life (10% skeleton per year)
- repairs microfractures, releases minerals into blood, reshapes bones in response to use/disuse.
How does mature bone remain metabolically active?
- involved in its own maintenance, growth and remodeling
- influences body by exchanging minerals with tissue fluid
- ex: disturbance of calcium homeostasis disrupts nervous and muscular tissue
How are minerals added to and removed to bone tissue?
mineralization (deposition): calcium phosphate and ions are taken from blood and deposited into bone
- osteoblasts produce collagen fibers that spiral the length of the osteon
- Fibers become encrusted with minerals:
- hydroxyapatite crystals form at solubility product (critical level of calcium and phosphate concentration)
- first few crystals act as seeds that attracts more calcium and phosphate from solution
Calcium homeostasis
- Phosphate is a component of DNA, RNA, ATP, phospholipids and pH buffers
- Calcium is used for neuron communication, muscle contraction, blood clotting and exocytosis
- minerals deposited into skeleton, withdrawn when they are needed
- hypocalcemia (less calcium): changes membrane potential, overexcited nervous system leads to tetany, muscle spasms
- hypercalciemia (more calcium - rare): ion channels less responsive; nerve and muscle less excitable leading to muscle weakness, slow reflexes, heart attacks
Calcitrol (most active form of vitamin D)
- produced by actions of the skin, liver and kidneys
- increases calcium absorption by small intestines, increases calcium resorption from the skeleton
- calcitrol is necessary for bone deposition which helps provide adequate calcium and phosphate
- too little calcitrol leads to soft bones (rickets in children, osteomalacia in adults)
Other chemicals/hormones affecting bones
- 20 or more hormones, vitamins, and growth factors affect bone tissue
- bone growth is rapid in puberty and adolescence
- estrogen has the strongest effect on bone growth (stimulates multiplication of osteogenic cells, matrix deposition by osteoblasts, chondrocytes mutliplication and hypertrophy in metaphyses)
- females grow faster, males grow longer and taller
-anabolic steroids cause growth to stop:
epiphyseal plates close prematurely and results in short stature
Name and describe several bone disorders.
Osteoporosis: most common bone disease
- severe loss of bone density
- bones lose mass/become brittle due to loss of organic matrix and minerals
- impacts spongy bone the most since its the most metabolically active
- postmenopausal women are most at risk
Rickets: softness of bones in children
Osteomalacia: softness of bones in adult
Spinal osteoporosis
Stress fracture vs Pathological fracture
Stress fracture: break caused by abnormal trauma to bone like a fall
Pathological fracture: break in a bone weakened by disease like bone cancer and osteoporosis
- Hematoma formation
fracture repair
blood vessels tear when bone breaks, bruise forms as it bleeds
- Soft Callus formation
fracture repair
uses collagen fibers and fibrocartilage to stabilize the break
- Hard Callus Formation
fracture repair
“rough patch” temporary bone collar that fuses the broken pieces together
- Bone Remodelling
fracture repair
osteoclasts clean remaining fragments, shape bone to original form.
What are joints and how are their names derived?
Joints/articulations: any point where 2 bones meet regardless if the bones are movable at that interface
Joint names are derived from the names of the bones involved, joints classified in the manner in which bones are bound
Fibrous joints
-sutures
loc: cranium
collagen attaches sutures together
-bony joint: synostosis (old cranial sutures) without fibrous connective tissue
-gomphoses
loc: between teeth and socket
bundles of collagen, periodontal ligaments
-syndesmoses
loc: leg (tibia and fibula)
forearm (radius and ulna)
sheet of connective tissue along the length of bones
Cartilaginous joints
Synchondrosis: bones joined by hyaline cartilage
Symphysis: 2 bones joined by fibrocartilage
