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69 Cards in this Set

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What are the functions of the skeletal system?

- Framework


- Support


- Protection


- Movement - bones act like levers for muscles to use


- Hematopoiesis (formation of red blood cells)


- RBC's, WBC's, platelets


- Mineral Storage

Cartilage

- Made up of chondrocytes


- Has a flexible matrix


- Undergoes mitosis


- Is used as the tissue on which the embryonic skeleton develops

Picture of cartilage types on the skeleton

What is bone classification based on?

Location: - axial skeleton (skull, ribs, spine)


- Appendicular skeleton (long bones of upper and lower limbs, hips, hands, feet)


Bone shapes:


- Long bone (humerus, i.e.)


- Irregular bone (vertebra, i.e.)


- Flat bone (sternum, i.e.)


- Short bone (talus, tarsals, carpals, etc.)

Bone structure - what is bone tissue and what are the types of bone cells?

Bone tissue (Osseous tissue) is connective tissue




Types of Bone cells:


-Osteogenic stem cell


-Osteoblast


-Osteocyte


-Osteoclast

Osteogenic stem cell (pic)

What cell is this a picture of?  What is its function?

What cell is this a picture of? What is its function?

Osteoblast




- matrix-synthesizing cell responsible for bone growth




- young cell that produces osteoid

What cell is this a picture of?  What is its function?

What cell is this a picture of? What is its function?

Osteocyte




- mature bone cell that monitors and maintains the mineralized bone matrix

What cell is this a picture of?  What is its function?

What cell is this a picture of? What is its function?

Osteoclast




- bone-resorbing cell




- breaks down the bone; important for bone remodeling

What are the bone types? (textures)

1) Compact bone (lamellar)


- dense outer layer




2) Spongy (cancellous) bone


- honeycomb of trabeculae

spongy and compact bone picture

What are the different membranes of the bone?

1) Periosteum


- a dense layer of vascular connective tissue enveloping the bones EXCEPT at the surfaces of the joints.



2) Endosteum


- a thin vascular membrane of connective tissue that lines the surface of the bony tissue that forms the medullary cavity of long bones


- AKA lines the hollow tube of a long bone

What is the structure of short, flat, and irregular bones?

- Consist of thin plates of periosteum covered compact bone


- spongy bone is sandwiched between the 2 layers of compact bone


- the layer of spongy bone is called "Diploe"


- the bone marrow is contained in between the trabecula cavities

Structure of flat bone (PIC)

Endosteum and Periosteum pic

Structure of a long bone (PIC)

What is the Diaphysis?

Diaphysis: the shaft of the bone (long bone)


- thick collar of compact bone on the periphery encircling spongy bone on the inside


- covered with periosteum



- Medullary cavity: hollow central part, filled with bone marrow



What is the Epiphysis?

Epiphysis: are the bone ends



- areaswhere the bone makes a joint



- Covered with articular cartilage

Histology of compact bone (PIC)

Slide of compact bone tissue (PIC)

What gives bones the hard consistency and flexibility?

Hard consistency - calcium






Flexibility - collagen

What is the chemical composition of bone?

Organic components: all the bone cells;


- Osteoid: ground substance and collagen fibers




Inorganic components: 65% bone mass


- hydroxyapatites (hydroxyapatite crystals)


- largely calcium phosphate salts


- contribute to the exceptional hardness of bones

What is the process of bone formation called?

Osteogenesis or Ossification




Depending on the particular stage of life it is described as:


- Bone formation


- Bone growth


- Bone remodeling

What are the processes of bone formation in the developing embryo and fetus?

1) Endochondral ossification


- Cartilage model - long bones made this way




2) Membranous ossification


- Membranous tissue - flat bones




- Both begin around 2nd month of gestation*

What are the steps to Endochondral Ossification? (How are long bones made?)

1) Bone collar forms around diaphysis of the hyaline cartilage model


2) Cartilage in center of the diaphysis calcifies and develops cavities


3) The periosteal bud invades the internal cavities and spongy bone forms


4) The diaphysis elongates and a medullary cavity forms. Secondary ossification centers appear in the epiphyses (at birth)
5) The epiphyses ossify. When completed, hyaline cartilage remains only in the epiphyseal plates and articular cartilages (childhood to adolescence)

Endochondral ossification (PIC)

What are the steps of Intramembranous Ossification?

1) Ossification centers appears in the fibrous connective tissue membrane


2) Osteoid is secreted w/in the fibrous membrane and calcifies


3) Woven bone and periosteum form


4) Lamellar bone replaces woven bone, just deep to the periosteum. Red marrow appears

Which type of ossification is this? 


What is occurring?

Which type of ossification is this?




What is occurring?

Endochondral ossification




- bone collar is forming around the diaphysis of the hyaline cartilage model

Which type of ossification is this? 


What is occurring?

Which type of ossification is this?




What is occurring?

Endochondral ossification




- cartilage in the center of the diaphysis calcifies and then develops cavities

Which type of ossification is this? 


What is occurring?

Which type of ossification is this?




What is occurring?

Endochondral ossification




- the periosteal bud is invading the internal cavities and spongy bone forms

Which type of ossification is this? 


What is occurring?

Which type of ossification is this?




What is occurring?

Endochondral ossification




- the diaphysis elongates and a medullary cavity forms. Secondary ossification centers appear in the epiphyses

Which type of ossification is this? 


What is occurring?

Which type of ossification is this?




What is occurring?

Endochondral ossification




- The epiphyses ossify. When completed, hyaline cartilage remains only in the epiphyseal plates and articular cartilages

Which type of ossification is this? 


What is occurring?

Which type of ossification is this?




What is occurring?

Intramembranous ossification




Ossification centers appear in the fibrous connective tissue membrane




- selected centrally located mesenchymal cells cluster and differentiate into osteoblasts, forming an ossification center that produces the first trabeculae of spongy bone

Which type of ossification is this? 


What is occurring?

Which type of ossification is this?



What is occurring?

Intramembranous ossification



Osteoid is secreted within the fibrous membrane and calcifies



- Osteoblasts begin to secrete osteoid, which calcifies in a few days.


- trapped osteoblasts become osteocytes

Which type of ossification is this? 


What is occurring?

Which type of ossification is this?




What is occurring?

Intramembranous ossification




Woven bone and periosteum form




- Accumulating osteoid is laid down between embryonic blood vessels in a manner that results in a network (instead of concentric lamellae) of trabeculae called woven bone.


- Vascularized mesenchyme condenses on the external face of the woven bone and becomes the periosteum

Which type of ossification is this? 


What is occurring?

Which type of ossification is this?




What is occurring?

Intramembranous ossification




Lamellar bone replaces woven bone, just deep to the periosteum. Red marrow appears


- trabeculae just deep to the periosteum thicken. Mature lamellar bone replaces them, forming compact bone plates.


- Spongy bone (diploe), consisting of distinct trabeculae, persists internally and its vascular tissue becomes red marrow

What are facts about postnatal bone growth?

1) Growth in length is obtained by interstitial bone growth of the epiphyseal plates cartilage




2) Bone cells replace cartilage




3) Growth in thickness occurs by Appositional bone growth

Bone growth picture/diagram



What is bone growth in width called and how does it occur?

Appositional bone growth



- osteoblasts on the external bone surface lay osteoid and cause an increase in the bone diameter

Appositional bone growth pic



What is bone remodeling?

Bone remodeling: the ongoing bone deposition and bone resorption



- in healthy adults, bone mass remains the same



- it is coupled and coordinated by "packets" of adjacent osteoblasts and osteoclasts called "remodeling units"

What controls bone remodeling?

growth hormone (HGH)


thyroid hormone


parathyroid hormone


sex hormones


calcium


vitamin D

Picture comparing bone growth and bone remodeling



What are the hormonal controls of bone remodeling?

Normal blood calcium level: 9-11mg/100ml blood




Daily calcium reqt (birth-10yr): 400-800mg


(adult) : 1200-1500mg




Key hormones involved: parathyroid & calcitonin

How do the hormonal controls of blood calcium work?

Negative feedback mechanism, primarily controlled by parathyroid hormone (PTH)




1) drop in blood calcium level


2) Parathyroid glands release PTH


3) PTH stimulates osteoclasts to degrade bone matrix and release calcium


4) rise in blood calcium

Hormonal controls of blood calcium (diagram)



How do bones respond to mechanical stress?

Wolff's Law: a bone grows or remodels in response to forces or demands placed upon it





What are some observations that support Wolff's Law?

1) Handedness (right or left) results in bone of dominant arm being thicker and stronger




2) Curved bones are thickest where they are most likely to buckle




3) Trabeculae form along lines of stress




4) Large, bony projections occur where heavy, active muscles attach

What factors aside from mechanical stress affect bone growth?

1) Growth hormone




2) Thyroid hormones




3) Testosterone and estrogens

What is the role of vitamins in bone formation?

Vitamin A - important in growth and bone health




Vitamin C - help collagen synthesis




Vitamin D - helps body absorb calcium

What are some examples of bone diseases?

- Rickets




- Osteomalacia




- Osteoporosis

What is Rickets disease?

- A nutritional disorder that can develop from lack of vitamin D, calcium, or phosphate


- Rickets leads to poor functioning of a bone’s growth plate (growing edge), softened and weakened bones, stunted growth, and, in severe cases, skeletal deformities.

What is Osteomalacia?

- a softening of the bones usually due to lack of vitamin D




- soft bones are more likely to bow or fracture

What is osteoporosis?

- a medical condition in which the bones become brittle and fragile from loss of tissue, typically as a result of hormonal changes, or deficiency of calcium or vitamin D

How are fractures described?

1) Location




2) External appearance




3) nature of the break

What are bone fractures classified due to?

1) Position of bone ends after fracture


- aligned, non-aligned


2) Completeness of break


- complete, incomplete, multiple breaks


3) Orientation of break to long axis of bone


4) Whether or not bone ends penetrate skin


- open or closed

What are the main stages in the healing of fractures?

1) Hematoma formation




2) Fibro cartilaginous callus formation (soft callus)




3) Hard callus formation




4) Bone remodeling

How does hematoma formation occur?

1) Blood vessels are broken




2) Blood escapes




3) Blood collects




4) Swelling occurs

What is occurring here? 

What is occurring here?

This is the healing after a fracture




- the fibrocartilaginous callus is forming




(soft callus formation)

What is occurring here?

What is occurring here?

Healing process after a fracture




- hematoma formation

What is occurring here? 

What is occurring here?

Healing process after a fracture




- hard callus formation

The healing of a fracture (picture)



What are common types of fractures?

1) Comminuted


2) Compression


3) Spiral


4) Epiphyseal


5) Depressed


6) Greenstick

What is a comminuted fracture?

- bone fragments into 3 or more pieces




- more common in older persons whose bones are more brittle

What is a compression fracture?

- bone is crushed




- common in porous bones subjected to extreme trauma, such as in a fall


(vertebra for example)

What is a spiral fracture?

- Ragged break occurs when excessive twisting forces are applied to a bone




- common sports fracture

What is an epiphyseal fracture?

- Epiphysis separates from the diaphysis along the epiphyseal plate



- tends to occur where cartilage cells are dying and calcification of the matrix is occurring


What is a Depressed fracture?

- broken bone portion is pressed inward




- typical of skull fracture

What is a greenstick fracture?

- bone breaks incompletely similar to how a green twig would break




- common in children whose bones have relatively more organic matrix and are more flexible than the bones in adults