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skeletal system bones anatomy physiology norcocollege 2a sternberg
skeletal system, bio 2a @ Norco College w/ Dr. Sternberg
Describe and name the Long Bones.
Long, longitudinal axis & expanded ends
: humerus, ulna (medial), radius (lateral), metacarpals (5), phalanges
: femur, tibia (medial), fibula (lateral), metatarsals, phalanges
Describe and name the Short Bones.
Equal in length, width & thickness; shaped irregularly
Carpal Hand Bones (8) Tarsal Foot Bones (7)
1. Scaphoid 1. Calcaneus
2. Trapezium 2. Talus
3. Trapezoid 3. Cuboid
4. Triquetral 4. Navicular
5. Pisiform 5. Lateral (3) Cuneiform
6. Hamate 6. Inter. (2) Cuneiform
7. Capitate 7. Medial (1) Cuneiform
Describe and name the Flat Bones.
More thin and curved rather than "flat"
Bones of the Cranium (skull):
Other Flat Bones:
Ribs Scapulae (shoulder blades)
Clavicle Sternum (breast bone)
Oz Coxae ("hip bones")
Describe and name Irregular Bones.
These bones don't fit neatly in any other category.
1. Vertebrae, sacrum, coccyx
3. Two of the cranial bones:
4. Facial Bones:
Inferior nasal concha (2)
5. Ear ossicles:
Malleus, Incus, Stapes
Describe and name the Sesamoid Bones.
Small bones embedded within tendons, usually where tendons pass over the joint of a long bone.
Help overcome compression forces, increasing mechanical efficiency of joints--# varies among people
Within tendon of quadriceps femoris (thigh muscle)
: pisiform carpel bone
Within tendons of flexor carpi ulnaris
Name and describe the Accessory Bones.
Commonly found in feet
Occur where developing bones don't fuse properly
Look like extra/broken bones in x-rays
*Sometimes small clusters between flat skull bones. ("Sutural" or "Wormian" bones.)
Expanded end portion
Articulates (forms a joint)
Describe: Articular Cartilage
A layer of hyaline cartilage
Shaft of the bone
Tough, vascular covering of the fibrous tissue
Fibers are continuous with ligaments and tendons
Functions in bone repair
Describe: Medullary Cavity
Hollow bone portion of diaphysis of long bone
Continuous with spaces of spongy bone
Squamous epithelial lining of the medullary cavity and spaces in spongy bone
Describe: Compact bone
Solid, strong, resistant to bending
Describe: Spongy Bone
Numerous branching bony plates-"Trabeculae"
Interconnecting spaces reduce weight
Both types usually present in any bone
Mostly spongy bones
: short, flat, irregular
Soft, net-like connective tissue
Irregular spaces of spongy bone (red)
Medullary cavity of long bones (yellow)
Describe: Red Marrow
Forms erythrocytes (RBCs)
Forms leukocytes (WBCs)
Forms thrombocytes (Platelets)
Red color due to hemoglobin
Describe: Yellow Marrow
Fat storage--adipose tissue
Found in medullary cavities of long bones
Name the Bone cells
Bone cell capable of synthesizing new bone matrix
Usually found in the growing portion of bone
Main cell of mature bone tissue
Regulates the concentration of calcium in body fluids by helping release calcium from bone tissue into blood
Multinuclear bone-destroying cell
Usually found where bone is resorbed during normal growth
Describe the general process for Osteogenesis.
1. Connective tissue is laid down.
2. Periosteum is formed from the connective tissue.
3. Blood vessels and undifferentiated connective tissue cells begin to fill the developing area.
4. The undifferentiated connective tissue differentiates into osteoblasts.
5. Osteoblasts deposit bone tissue.
Describe Intramembranous Ossification (Interstitial growth)
Occurs in Flat bones
1. Layers of undiff. CT appear in the site of a future bone.
2. CT cells arrange around blood vessels within the layers.
3. CT differentiates into osteoblasts.
4. Osteoblasts form a spongy bone matrix around themselves which then forms trabeculae.
5. When the bony matrix (trabeculae) surround the osteoblasts, they become osteocytes.
6. As the matrix fills in, some spongy bone becomes compact bone.
7. Primitive tissue on the surface becomes the periosteum.
Describe Endochondral Ossification (Intracartilaginous Bone Formation)
1. Mesenchyme cells multiply and accumulate in the site of a future bone, forming a rough outline of future bone.
2. Mesenchyme cells differentiate into chondroblasts; form matrix.
2. Hyaline cartilage "bone model" is made.
(Cells at edge become perichondrium, then differentiate into fibroblasts)
3. Cartilaginous bone model grows at ends--Interstitial growth bc matrix added internally.
Midportion chondrocytes greatly enlarge
Phosphatase enzymes are secreted.
4. Cartilaginous bone model grows in width--Appositional growth.
5. Perichondrium invaded by capillaries.
Some perichondrium (osteogenic cells) become osteoblasts & osteocytes.
6. Thin bone layer forms in mid-cartilaginous bone.
CT around this bone becomes periosteum.
Innermost periosteum can make chondrocytes in adulthood.
7. Calcified cartilage in mid-bone breaks down and blood vessels, osteocytes & osteoblasts fill region--forms ossification center.
Osteoblasts make cancellous bone.
8. Ossification center expands in both directions of bone.
Cartilage breaks down, replaced by cancellous bone = shaft/diaphysis of bone.
Center is resorbed, becomes marrow cavity.
9. Appositional growth
resorbed from medullary cavity while it is deposited by periosteum.
Describe the growth of Endochondral Bone.
1. Cartilage in center of diaphysis (1* Ossification Center) is replaced.
Osteoblasts deposit a thin layer of compact bone by interstitial ossification.
Bone forms center--> end.
2. At epiphysis, 2* Oss. Ctr. appears, remains cartilaginous as it grows.
Spongy bone forms in all directions.
3. Compact bone is deposited in diaphysis of 1* Oss. Ctr.
4. Spongy bone deposited in epiphysis of 2* Oss. Ctr.
5. Bone changes shape as it grows.
Continuous and extensive bone remodeling
Haversian systems replaced with new ones.
True or False: Can bones continue to grow even after the onset of sexual maturity?
True or False: Intramembranous bones grow by way of the periosteum?
True or False: Endochondral bones enlarge in size with excessive weight gain.
True or False: The precise mechanism for bone remodeling is known.
The precise mechanism is unknown.
True or False: Bone decalcifies in response to stress on the matrix.
Bone CALCIFIES in response to stress on the matrix.
True or False: Bone decalcifies in zero gravity.
True or False: Weak electric currents speed up bone repair.
True or False: Bone responds to stress imposed by body weight and muscle movement.
The term for the adipose tissue that fills the hollow shaft of the diaphysis of a long bone.
When does the bony epiphysis fuse with the diaphysis?
When the organism reaches adulthood.
In mammals, what constitutes the core of the bony epiphysis?
Spongy bone and red marrow.
Prior to becoming an adult, what is the term for the structure that separates the epiphysis from the ossified diaphysis?
Describe the Endochondral Ossification of Long Bones.
1. Mesenchyme cells form a hyaline cartilagous template.
The cartilaginous template is contained in a dense irreg. CT called a perichondrium.
2. Perichondrium differentiates into a periosteum.
Periosteum deposits a thibn outer layer of intramembranous bone (around outer diaphysis, beneath periosteum)
3. Blood vessels enter cartilage template, & mesenchyme cells differentiate into osteoblasts.
4. Osteoblasts lay down an ossified bony matrix that replaces cartilage with replacement bone.
5. In the developing replacement bone, some mesenchyme diff. into osteoclasts.
Osteoclasts resorb bony matrix, forming hollow medullary cavity.
The cavity runs the length of the diaphysis and is surrounded by solid lamellae of bone.
6. Haversian systems develop around nerve/blood supply canals in developing matrix.
Osseus tissue is deposited in concentric cylinders called osteons.
Ossification can occur at one or more secondary center to replace cartilage.
True or False: Epiphyseal bone is mostly lamellar (spongy).
What is the term for the marrow cavity that develops in the epiphysis?
The growth and development of bones is best understood in what organisms?
Besides growth in size, how else do bones grow?
Bone remodeling to maintain their shape
Where does diaphysis length increase?
Cartilaginous plates separating the diaphysis and epiphysis
What happens to the epiphyseal plates once a mammal reaches adulthood?
The epiphyseal plates calcify and become epiphyseal lines and growth in bone length stops
How do long bones grow in width (transverse diameter)?
Osteoblasts deposit bone at the outer surface in the periosteum while osteoclasts resorb bone in the medullary cavity of the endosteum.
Name the 4 Regions of the Epiphyseal Plate.
1. Zone of Resting or Reserve
2. Zone of Proliferation
3. Zone of Maturation
4. Zone of Calcification
Describe the Zone of Resting (Reserve, Cartilage).
Consists of hyaline cartilage
Chondrocytes are irregularly spaced next to the bone of epiphysis
: Attach cartilaginous plate to epiphyseal bone
Blood vessels carrying nutrients enter the epiphyseal plate from the epiphysis side, through this zone.
Chondrocytes in the resting zone do not contribute to bone length.
Describe the Zone of Proliferation.
Chondroblasts are stacked on eachother
It is considered the Mitotic Zone due to new chondrocytes made here to replace the dead ones at the diaphyseal end of the epiphyseal plate.
Partly responsible for expansion of length of the epi. plate.
Describe the Zone of Maturation.
Chondrocytes are larger, stacked and have lacunae that are more visible.
Chondrocyte hypertrophy also contributes to growth of length.
Older cells are closer to the diaphysis.
Chondrocytes in the Maturation zone dies when matrix calcifies.
Describe the Zone of Calcification.
This zone functions as attachment to the diaphysis.
Mature chondrocytes secrete phosphatase.
Calcification of extra cellular matrix occurs, cutting off nutrient supply, causing chondrocytes to die.
Capillaries, osteoblasts and osteoclasts travel to this zone.
Osteoclasts remove dead, calcified cartilage.
Osteoblasts lay new bone down on calcified spicules.
Bone resorption occurs at the boundary of marrow cavity.
Describe Woven bone.
It is the bone initially made during Intramembranous Ossification and Endochondral Ossification.
Collagen fibers run in all directions (not parallel like lamellar bone).
Not suitable for stress and strain.
Provides framework for lamellar bone to be laid down for Bone Remodeling.
Describe Lamellar Bone.
After woven bone is laid down, osteoclasts replace it with lamellar bone.
Lamellar bone is strong and stable.
It is deposited in concentric rings around a blood vessel.
Osteoblasts in lacunae become osteocytes and are connected to the blood supply through the cannaliculi.
Describe Cortical Bone.
Has very distinct and highly-ordered osteons in outer compact layers near external surface of bone.
Is a thin shell-like layer.
Describe Cancellous (Spongy) Bone.
This is the central portion of most bones.
It is interspersed with blood-filled cavities called Cancellae.
The blood in Cancellae nourishes osteocytes.
(This arrangement takes the place of Haversian Systems in Compact (Cortical) bone).
Function of Vitamin A.
Function of Vitamin C.
Synthesis of collagen in bone matrix.
Function of Vitamin D.
Converts Vitamin D to 1,25 dihydroxycholecalciferol by a parathormone.
Affects calcium absorption from gut.
Function of Pituitary Growth Hormone.
Stimulates cartilage production in epiphyseal disks.
Function of Testosterone.
Steroidal growth from testes and adrenal cortex.
Promotes size and strength of bone growth (esp. long bones)
Stimulates protein synthesis, increasing bone matrix production.
Function of Estrogen.
Promotes closure of epiphyseal plates of long bones--terminates lengthening process.
Function of Parathyroid hormone.
Helps osteoclasts absorb Ca
Maintains a stable blood calcium level.
Converts Vit. D to 1,25 dihydroxycholecalciferol.
Affects calcium absorption from gut.
Affects deposition and reabsorption of bone.
Function of Calcitonin.
Promotes osteoblastic activity and deposition of bone
Bone is broken through completely
Occurs in adults (due to fully calcified bones)
Aka "green stick fracture"
Bone is not broken completely through
Occurs in children (due to the collagen content of bones)
Skin over the break is intact.
Bone pierces the skin
Splintered or fragmented bone
Occurs in an already diseased bone
What are the 3 stages of a Fracture Healing?
2. Fibrocartilaginous Callus
3. Osseus Callus
How long does it take to heal a fracture?
What is the primary requirement for a fracture to heal correctly?
The bones must make contact with one another.
i.e., "the fracture must be reduced"
Describe the Procallus Stage of a healing fracture.
This stage initially binds the fracture together.
It takes 48 hours for a blood clot (hematoma) to be converted into soft tissue (procallus).
Loose network of fibers is laid down.
RBCs are destroyed, stimulating an inflammatory reaction (swelling, edema)
Increased blood flow and white cells (by mast cells).
- Macrophages phagocytize debris
- Fibroblasts begin to repair by laying down CT
Describe the Fibrocartilaginus Callus Stage of a healing fracture.
This occurs on the 3rd or 4th day.
Fibroblasts lay down fibrous CT network.
New chondrocytes form cartilanginous spicules throughout callus.
After 1 week, early forms of newly formed bone and cartilage are found in the callus.
Osteoblasts and chondroblasts are made from the periosteum and endosteum of the fracture site.
Inflammatory response subsides over the next few days.
Describe the Osseus Callus Stage of a healing fracture.
This occurs at the 2-3 week mark of the fracture.
The healing fractured bone is wider in diameter than the original bone.
In this stage remodeling begins and continues until it is healed and almost undetectable.