Skeletal System Flashcards
Functions of Skeletal System
Support.
Storage of minerals (calcium) electrolyte balance.
Storage of lipids (yellow marrow).
Blood cell production (red marrow).
Protection (brain, spinal cord, heart, lungs, etc.)
Leverage (force of motion).
Acid base balance.
Long Bones
Are long and thin. Are found in arms, legs, hands, feet, fingers, and toes. (Extremities excluding the wrist and ankle bones).
Provide strength, structure, mobility and articulation with other bones.
Ex: femur, tibia, fibula, metatarsals, and phalanges.
Short Bones
Are small and think. About as tall as wide. Provide strength and support. Work as stabilizers. Ex: ankle bones( tarsals)
Flat Bones
Are thin with parallel surfaces. Vary greatly in shape and size. Shield and protect organs from harm. Are found in the skull, sternum, ribs, scapula, clavicle, and pelvis. Base for muscular attachment.
Sesamoid Bones
Inside tendons (patella of knee)
Irregular Bones
Have complex shapes. Spinal vertebrae, sacrum, coccyx, sphenoid, zygomatic, mandible.
Osteogenic
Cells in endosteum, periosteum or central canals give rise to new osteoblasts. Arise from embryonic fibroblasts. Multiply continuously.
Osteoblasts
Mineralize organic matter of matrix(osteogenesis)
Osteocytes
Are osteoblasts trapped in the matrix they formed. Cells in lacunae connected by channels called canaliculi.
Osteoclasts
Develop in bone marrow by fusion of 3 to 50 stem cells. Resides in pits that they are into the bone. Secrete acids and protein digesting enzymes.
Homeostasis in Bones
Bone building by osteoblasts and bone recycling by osteoclasts must balance. More breakdown then building than bone gets weak. Exercise causes osteoblasts to build bone.
Bone matrix
Deposits of calcium salt.
Bone cells within lacunae organized around blood vessels.
Canaliculi
Form pathways for blood vessels.
Exchange nutrients and wastes.
Bone (osseous) tissue
Dense supportive connective tissue.
Contains specialized cells.
Produces solid matrix of calcium salt deposits.
Around collagen fibers.
Epiphyseal plate
Growth plate.
Periosteum
Covers shaft of bone. Outer fibrous layer of collagen. Inner osteogenic layer of bone forming cells.
Inorganic
2/3 of bone matrix is inorganic. 85% of crystals are hydroxyapatite. (Calcium phosphate salt) 10% calcium carbonate. Which incorporates other calcium salts and ions.
Organic
1/3 of bone matrix is organic. Protein fibers (collagen, protein-carbohydrate complexes).
Compact bone
Contains osteons (the basic unit of mature compact bone). Osteocytes are arranged in concentric lamallae. Around a central canal containing blood vessels.
Perforating (volkmann) canals
Lie at right angles to the central canal. Connect blood and nerve supply between marrow and central canals.
Concentric lamallae
Lamallae wrapped around the long bone. Binds osteons together.
Spongy bone
Does not have osteons. The matrix forms an open network of trabeculae. Tribeculae have no blood vessels. Has osteocytes in lacunae and canniculi. Provides strength with little weight. Trabeculae develop along Bones line of stress. Help the bone to resist stress.
Red Marrow
Space between tribeculae is filled with red bone marrow. Has blood vessels, forms red blood cells, supplies nutrients to osteocytes, in children red marrow in most marrow cavities, in adults limited to skull, vertebrae, ribs, sternum, part of pelvic girdles and proximal heads of femur and humerus.
Yellow Marrow
I’m adult bones, most Marrow turns to yellow. Yellow because it stores fat.
Periosteum
Covers all bones except parts enclosed in joint capsules. Made up of an outer fibrous layer and an inner cellular level.
Functions: isolate bone from surrounding tissues, provide a route for circulatory and nervous supply, participate in bone growth and repair.
Endosteum
An incomplete cellular layer. Lines the marrow cavity, covers trabeculae of spongy bone, lines central canals. Contains osteoblasts, osteoprogenitor cells, and osteoclasts. Is active in bone growth and repair.
Endochondral Ossification
Bone develops by replacing hyaline cartilage.
Intramembraneous Ossification
Bone develops within membranes. Develops within a fibrous connective tissue sheet similar to dermis connective tissue (mesenchymal tissue). Produces flat bones such as clavicle and skull bones.
Embryonic bone development
Bone develops from preexisting hyaline cartilage. Starts at 6 weeks in uterine and continues into the early 20s. Bone growth stops at 25. Diaphysis.
Articulate cartilage
Covers joint surface
Epiphyseal Plates
Cartilage between primary and secondary marrow cavities. Growth plate provides for increase in length of bone during childhood and adolescence. By early twenties, growth plates are gone and primary and secondary marrow cavities are united.
Bone growth and remodeling
Continues throughout life (bones increase in lenght(height) and bones increase in width.
Postnatal Bone Growth
Long bones lengthen entirely by interstitial growth of epiphyseal plate(growth plate). Present at end of long bone from infancy through adolescence. Cartilage replaced with bone. Epiphyseal line is left behind when cartilage is gone.
Bone growth
Bones increase in width and they lengthen (apposition growth). Osteoblasts of inner periosteum secrete matrix in layers parallel to the bone surface concentric lamellae. Osteoclasts dissolve bone on inner surface to increase marrow cavity.
Hormonal Regulation of Bone Growth
Growth of bones in youth adulthood is controlled by hormones. Growth hormone is the important stimulus during infancy and childhood , regulated by thyroid hormone. At puberty, sex hormones estrogen in females and testosterone in males promote a growth spurt and feminization/masculinization of skeletal parts. Hormones govern closure of epiphyseal plate.
Ion imbalances
Changes in phosphate levels = little effect. Changes in calcium can be serious.
Hypocalcemia
Deficiency of blood calcium. Causes excitability of nervous system. Muscle spasms, tremors, or tetany. Laryngospasms and suffocation.
Hypercalcemia
Excess of blood calcium. Depressed nervous system. Muscle weakness and sluggish reflexes, cardiac arrest.
Calcitonin and Parathyroid hormone(PTH)
Regulate calcium and phosphate levels. Bones: where calcium is stored.
Digestive tract: where calcium is absorbed.
Kidneys: where calcium is excreted.
Parathyroid Hormone (PTH)
Produced by parathyroid glands in neck. Increases blood calcium ion levels by:
Stimulate osteoclasts to increase bone resorption.
Increasing intestinal absorption of calcium.
Decreases calcium exertion at kidneys.
Calcitonin
Secreted by C cells (parafollicular cells) in thyroid.
Decreases calcium ion levels by:
Inhibiting osteoclasts activity.
Increasing calcium excretion at kidneys.
Healing of fractures
Normally 8-12 weeks.
Stages of healing:
Fracture hematoma, clot forms then osteogenic cells for granulation tissue.
Soft callus, fibroblast produce fibers and fibrocartilage
Hard callus, osteoblasts produce a bony collar in 6 weeks.
Remodeling in 3 to 4 months, spongy bone replaced by compact bone.
Osteoporosis
Severe bone loss. Affects normal function. Over age 45, occurs in 29% of women and 18% of men.
Menopausal Effects
Estrogens and androgens help maintain bone mass. Bone loss in women accelerates after menopause.
Joint functions
Link the bones of the skeletal system into a functional whole. Supports the body, allows effective movement, protects softer organs.
Joint Classification
The amount of movement the joint can make.
Synarthrosis: no movement(most stable)
Amphiarthrosis: little movement(stable)
Diarthrosis: more movement freely moveable joint(most unstable)
Accessory Ligaments
Support, strengthen joints. Attach bone to bone. Sprain=ligaments with torn collagen fibers.
Tendons attach to muscles around joint. Help support joint.
