Skeletal system phisiology

Skeletal Cartilage

Made of highly resiliant, molded cartilage tissue that consists primarily of water. Contains no blood vessels or nervs

Pericondrium

Layer of dense connective tissue surrounding cartilage like a girdle. Helps cartilage resist outward expansion, contains blood vessels for nutrient delivery to cartilage

Cartilage is made of

Chondrocytes, cells encased in small cavities (lacunae) within jelly ECM

Hyaline cartilage

Provides support, flexibility, resilience. Most abundant type, contains only collagen fibers. Joints, costal ribs, respiratory and nasal cartilage

Elastic Cartilage

Similar to hyaline, but has elastic fibers. External ear and epiglottis

Fibrocartilage

Thick collagen fibers, has great tensile strength. Menisci of knee, vertebral discs

Appositional Growth

cartilage forming cells in perichondrium secrete matrix against external face of existing cartilge. New on top of the surface

Interstitial growth

Chondrocytes within lucunae divide and secrete new matrix, expanding cartilage from within. New matrix made within the cartilage

Calcification of cartilage

occurs during normal bone growth in youth and old age. Hardened cartilage is NOT THE SAME as bone

Functions of bones

Support, protection, movement, mineral and growth factor storage

Support

for body and soft organs

protection

protect brain, spinal cord, vital organs

movement

levers for muscle action

mineral and growth factor storage

calcium and phosphorus and growth factor reservior

Blood cell formation

Hematopoiesis occurs in red marrow cavities of certain bones

Tryglyceride (fat) storage

fat, used for an energy source is stored in bone cavities

Hormone Production

OSTEOCALCIN secrete by bones helps to regulate insulin levels and metabolism

Axial Skeleton

long axis of body, skull vertebral column, rib cage

Appendicular skeleton

bones of upper and lower limbs, girdles attaching limbs to axial skeleton

Long bones

longer than they are wide, limb bones

short bones

cube shaped in wrist and ankle, sesamoid bones form within tendons, vary in size and number in people

Flat bones

thin flat slightly curved. Sternum, scapulae, ribs, most skull bones

irregular bones

complicated shapes. Vertebrae and hip bones

Bones are what

Organs because they contain different types of tissues

Tissues in bone

Mostly osseous tissue, but has nervous, cartilage, fibrous connective, muscle cells, and epithelial blood cells

3 levels of structure

Gross, microscopic, chemical

Compact bone

dense outer layer on every bone that appears smooth and solid

spongy bone

made of honeycomb of small, needle like or flat pieces of bone called TRABECULAE

Structure of short, irregular and flat bones

Thin pates of spongy, covered by compact. Compact sandwiches between connective tissue membranes.

Periosteum in short, irregular, flat

covers OUTSIDE of compact bone

Endosteum in short irregular flat

covers INSIDE of compact bone

Bone marrow location on short flat irregular

scattered throughout spongy bone, no cavity

Hyaline cartilage

covers area of bone that is part of MOVABLE joint

Long bone structure

Diaphysis, epipyses, membranes

Diaphysis in long bone

tubular shaft that forms long axis of bone, filled of compact bone surrounding central medullary cavity that’s filled with yellow marrow

Epiphyses in long bone

bone ends of compact bone externally, and spongy internally. Articular cartilage covers the articular surfaces on the joints

Epiphyseal line in long bone

Remnant of childhood epiphyseal plate where bon growth occurs`

Epiphyseal plate

where bone growth occurs in childhood

Membranes

Periosteum or endosteum

Periosteum

white, double-layered membrane that covers external surfaces except for joints

Fibrous layer

Outer layer consisting of dense irregular connective tissue consisting of SHARPEYS fibers to secure to bone matrix

Osteogenic layer

inner layer abutting bone and contains primitive OSTEOGENIC stem cells that give rise to most all bone cells

Anchor points for tendons and ligaments

Membranes

Endosteum

Delicate connective tissue membrane covering internal bone surface. Covers trabeculae of spongy bone. Lines canals that pass through compact bone, osteogenic cells to differentiate into other bone cells

Hematopoietic tissue

Red marrow found within trabucular cavities of spongy bone and DIPLOE of flat bones.

Bone markings

sites of muscle, ligament, and tendon attachment on external surfaces. Involved in joint formation or conduits for blood vessels and nerves

Projection bone marking

outward bulge of bone, due to increased stress from muscle pull or is a modification for joints

Depression bone marking

bowl or groove cut out that can serve as a passageway for vessels and nerves, or plays a role in joints

Opening bone marking

hole or canal in bone that serves as passageway fro blood vessels and nerves

Cells of bone tissue

Osteogenic, Osteoblasts, osteocytes, bone-lining, osteoclasts

Osteogenic cells

Mitotically active stem osteoprogenior cells, active stem cells in periosteum and endosteum. when stimulated, they differentiate into OSTEOBLASTS or BONE LINING, some remain osteogenic

Osteoblasts

Actively mitotic bone forming cells that secrete unmineralized bone matrix called OSTEOID (made of collagen and calcium binding proteins, calcium is 90% bone protein)

Osteocytes

Mature bone cells in lacunae that no longer divide. Maintain bone matrix, act as stress or strain sensors. Respond to mechanical stimuli such as increased force on bone. Communicate info to OsteoBLASTS and osteoCLASTS so bone remodeling can occur

Bone lining cells

Flat cells on bone surfaces beloved to also help maintain matrix with osteoCYTES. On external surface, PERIOSTEAL. Internal, ENDOSTEAL.

Osteoclasts

Derived from same hematopoietic stems cells that become macrophages. Giant cells function in bone resorption. When active, cells in depressions of resorption bays. Have ruffled borders that serve to increase SA from enzyme degradation of bone, seal off area from surrounding matrix

Resoption

breakdown of bone

Compact bone (lamellar)

Osteon, canals and canliculi, interstitial and circumfrential lamellae

Osteon (Haversian system)

Structural unit of compact bone, elongated cylinder that runs parallel to the long axis of bone, acts of tiny weight-bearing pillars. Consists of several rings of bone matrix called LAMELLAE (collagen fibers that run in different directions in adjacent) Withstands stress and resist twisting.

Central (Haversian) canal

Runs through core of osteon, blood vessels and nerves fibers.

Perforating (volkmanns) canals

canals lined with endosteum that occur at right angles to central canal. Connect blood vessels and nerves of periosteum, medullary cavity, and central canal.

Lacunae canals

Small cavities that contain OSTEOCYTES

Canaliculi

hairlike canals that connect lacunae to each other and to central canal

Interstitial lamellae

Lamellae that are not part of osteon, some fill gaps between forming osteons, others are remnants of osteons cut by bones remodeling

Circumfrential lamellae

Just deep to periosteum, but superficial to endosteum, these layers of lamellae extend