Chapter 11 Flashcards
What are bones?
-rigid, mineralized structures
What are the functions of bones?
- Support
- Protection
- Movement
- Mineral Storage! -Calcium and Phosphorus
- Hematopoiesis! -Blood formation
What type of bone tissue is there?
- Cancellous (Trabeculae)
- Compact
What types of bone shapes are there?
- long
- short
- flat
- irregular
- sesamoid
What are examples of long bones?
- Femur
- Humerus
What are examples of short bones?
- Carpal
- Tarsal
What are examples of flat bones?
- Scapula
- Ribs
- Sternum
What are examples of irregular bones?
- Vertebrae
- Facial
What are examples of sesamoid bones?
-Kneecap
What components make up a long bone?
- Diaphysis: long, hollow shaft
- Epiphysis: knobs containing spongey bone
- Articular cartilage: thin layer of hyaline cartilage that covers joint surfaces
- Periosteum: outer dense covering of a bone that is not on joint surfaces; fuses to muscle fibers
- medullary cavity: marrow is stored here; hollow part of the diaphysis
- endosteum: lines the inside of the bone
What components make up a flat bone?
- Internal table: internal compact bone
- external table: external compact bone
- diploë: inner spongey bone
- periosteum: outer dense covering of a bone that is not on joint surfaces; fuses to muscle fibers
- endosteum: contain red marrow
What is bone tissue? What is it made of?
- Osseous tissue
- Made of connective tissue
- Extracellular matrix
What is the extracellular matrix composed of?
- Water: 25%
- Collagen: 25%
- Crystallized calcium phosphate: 50%
What is calcification? Performed by?
- depositing calcium phosphate to make a bone
- made by osteoblasts
What is the basic unit of dense bone?
- osteons
- Haversion system
What do osteons do?
- surround a central canal
- permit delivery of nutrients
- remove waste from bone cells
What are the osteons composed of? Describe and Function
- Lamellae: round layers
- Lacunae: small spaces in bone matrix
- Canaliculi: the cracks; canals that get nutrients from blood vessels to osteocytes
- Central canal: middle hole; contains blood vessels, lymphatic vessels, and nerves
- Transverse canal: connect central canals
What is cancellous bone made out of?
-Crisscrossing trabeculae
Where do you find cancellous bone?
-On the inside of the bone in the epiphyses
What does the cancellous bone contain?
-red bone marrow
What are the types of bone cells? Functions
- osteogenic stem cells: undergo mitosis to become osteoblasts (only one with mitosis)
- osteoclasts: breaks down bone to regulate blood calcium level
- osteoblasts: builds bones and adds calcium to bone (eventually becomes an osteocyte)
- osteocytes: exchange nutrients and wastes with the blood (forms when osteoblast becomes embedded in bone matrix)
What does red bone marrow do?
-produces red and white blood cells
Where do you find bone marrow?
-medullary cavity
Where do you find red bone marrow in infants?
-every bone
Where do you find red bone marrow in adults?
- ribs
- vertebrae
- ends of humerus
- pelvis
- femur
- sternum
What is yellow bone marrow made of?
-adipocytes
What does yellow bone marrow do?
-convert to red bone marrow in times of decreased blood supply
Why does the blood calcium level matter?
- nerve and muscle cells depends on calcium ions to function
- clotting requires calcium
- many enzymes require calcium as as a cofactor
What is the blood calcium level controlled by?
- parathyroid hormone
- calcitonin
What does the parathyroid hormone do?
- released when calcium levels are too low
- stimulates osteoclasts which releases calcium into the blood
What is the pathway for homeostasis when it comes to parathyroid hormone?
- Below normal calcium levels
- parathyroid hormone released
- osteoclasts are stimulated
- release of calcium into blood
What secretes parathyroid hormone?
-parathyroid gland
What does calcitonin do?
- is released when calcium level is too high
- stimulates the osteoblasts and stores extra calcium
- inhibits osteoclasts
What is the pathway for homeostasis when it comes to calcitonin?
- High blood calcium
- stimulates osteoblasts, inhibits osteoclasts
- calcium will move into the bones
- removal of calcium from blood
What secretes calcitonin?
-thyroid gland
What is ossification?
-the process by which bones form
What situations are involved in development of bone?
- formation in embryo
- growth
- remodeling
- fracture healing
What is intramembranous ossification?
-development of the ossification center
-Where does intramembranous ossification occur?
- flat bone of the skull
- mandible
How does intramembranous ossification occur?
- soft spots in the skull become ossified
- calcification
- formation of trabeculae
- development of the periosteum
How does the ossification center form?
-group of osteoblasts that secrete matrix
What cells help with ossification?
-osteoblasts secrete matrix and eventually become inclosed and become an osteocyte
What is endochondral ossification?
-bone formation spreads from the center to the ends
Where does endochondral ossification occur?
-most of the bones
How does endochondral ossification occur?
- Develop a hyaline cartilage (chondroblasts) model of bone; surrounded by perichondrium (connective tissue)
- Perichondrium develops into the periosteum at the diaphysis; osteoblasts from periosteum deposit bone; cartilage begins to calcify
- Blood vessels enter the midpoint of the diaphysis; “primary ossification center”
- Bone growth proceeds from the diaphysis toward each epiphysis; medullary cavity is developed
- Secondary ossification centers appear in the epiphysis; epiphyseal plate
- Ossification of the cartilage occurs nearest the diaphysis (allows bone growth)
How do bones grow in length?
- growth of cartilage at the epiphyseal plate
- replacement of cartilage by bone tissue
What is bone remodeling?
-bone continually renews itself
What happens if there is too much bone?
-bones become too thick and heavy
What happens if there is too little bone?
- weak bones
- osteoporosis
What happens if bone is too flexible?
- too much collagen and not enough calcium
- rickets
- osteomalacia
What factors influence bone remodeling and how?
- the balance of osteoblasts and osteoclasts
- minerals
- vitamins
- hormones
What do each of the vitamins do?
- vitamin A: stimulates osteoblasts
- vitamin C: synthesis of collagen
- vitamin D: helps build bone; increases the absorption of calcium
- vitamin K and B12: needed for synthesis of bone proteins
What are the hormones needed to affect bone growth?
- growth hormone: produced by pituitary gland
- thyroid hormone: promotes bone growth by stimulating osteoblasts
- insulin: promotes bone growth by increasing the synthesis of bone proteins
- estrogen and testosterone: growth spurt
- parathyroid hormone
- calcitonin
What are the different kinds of fractures?
- compound: bone protrudes through skin
- simple: does not break the skin
- comminuted: splintered, crushed, many pieces
- greenstick: one side is broken the other side bends
- impacted: one end of the fractured bone is forcefully driven into another
- Pott’s: fibula breaks with injury of the tibial articulation
- Colles’: fracture to radius in which the distal fragment is displaced
- stress: microscopic fissures in the bone
What is the process of healing a fracture?
- fracture hematoma: blood clotting on both sides
- procallus: islands of cartilaginous tissue; bridges broken ends
- bony callus: binds the broken ends
- remodeling
How is fracture repair initiated?
-initiated by bone death
What do fracture hematomas contain?
- inflammatory cells
- fibroblasts
- osteoblasts
- chondroblasts
- new capillaries
Describe cartilage.
- collagen fibers form in gel
- avascular
- chondrocytes
Describe bone.
- collagen fibers in calcified cement substance
- very vascular
- osteoclasts, osteoblasts, and osteocytes
Describe the similarities between bone and cartilage.
- many collagen fibers
- cells lie in lacunae
What is the perichondrium?
- fibrous covering of the cartilage that contains blood vessels
- gives cartilage nutrients by diffusion
What types of cartilage are there? Characteristics?
- hyaline: most common; contains collagen fibers
- elastic: contains elastic and collagen fibers
- fibrocartilage: has the most collagen; greatest strength but not flexible
Where can you find each type of cartilage?
- hyaline: covers articular surfaces of bone; costal cartilage; cartilage rings of trachea, bronchi, and nose
- elastic: ear, epiglottis, Eustachian (auditory) tubes
- fibrocartilage: in pubic symphysis and intervertebral discs
What is the function of cartilage?
- withstands great weight
- shock-absorber between bones
- strong and pliable support structure
- permits growth in long bones
How does cartilage grow?
- appositional growth: chondrocytes in the deep layer of the perichondrium divide and secrete matrix
- interstitial growth: cartilage cells within the cartilage divide and secrete additional matrix; childhood and early adolescence
How does exercise and aging affect bone tissue?
- the more exercise, the stronger the bone becomes
- age can cause: decrease bone mass by bone resorption
What are the two principle effects of agin on bone tissue?
- loss of bone mass caused by loss of calcium
- brittleness caused by decreased rate of protein synthesis (collagen)
What are the three different lamellae?
- Concentric: cylinder shaped; part of osteon
- Interstitial: layers between osteons
- Circumferential: runs along the circumference of the osteons
