Composed of 206 Bones Bones- Organs of the Skeletal System ▪ Provide points of attachment for muscles, ▪ Protect & Support softer tissues ▪ House blood-producing cells ▪ Store inorganic salts ▪ Contain passageways for blood vessels and nerves.
What are Bones Made Of? Bones are made of several different things: Bone Tissue Cartilage Dense connective tissue Blood Nervous Tissue
Osteocytes -Bone Cells -Transport nutrients & wastes to and from nearby cells. Extracellular Matrix of bone tissue is largely composed of collagen & inorganic salts - collagen= strength & resilience - inorganic salts= cause bone to be hard and resistant to crushing.
Processes- Bony projections that provide sites for ligaments & tendons to attach. Grooves & Openings- Form passageways for blood vessels & nerves.
Epiphysis- located at the end of bone. Forms a joint with another bone. Articular Cartilage: hyaline cartilage located on outer surface of epiphysis. (Articulating Portion) -Diaphysis- Shaft of the bone located between the epiphyses.
Periosteum- Tough, vascular covering of fibrous tissue that completely encloses the bone. Helps to form and repair bone tissue. Medullary Cavity- Semi rigid tube with a hollow chamber. Formed by compact bone Lined with a thin layer of bone forming cells= endosteum Filled with soft connective tissue known as marrow.
1. Compact Bone= Composes wall of diaphysis. Tightly packed NO Gaps Resists Bending
2. Spongy Bone Found in Epiphyses beneath a layer of thin compact bone. Helps to reduce the bone’s weight
Red Marrow= Functions in the formation of Red blood cells(erythrocytes), white blood cells(leukocytes), and blood platelets. In an adult found in: skull, ribs, sternum, clavicles, vertebra, and hipbones. Yellow Marrow= Replaces red marrow as we age. Stores fat and is inactive in blood cell production.
Bones can form 2 ways 1. Intramembranous bones originate between sheet-like layers of connective tissues. EX: Flat bones of the skull 2. Endochondral bones begin as masses of cartilage that bone tissue later replaces. Majority of bones in the skeletal system are endochondral. ▪ Osteoblasts- Bone forming Cells ▪ Osteoclasts- Break down calcified matrix.
1. Give shape to structures like the head, face, thorax, and limbs. 2. Provide support & protection EX: Bones of lower limbs, pelvis, & backbone support the body’s weight. Bones of the skull protect eyes, ears, & brain. Rib cage & shoulder girdle protect the heart and lungs.
3. Body Movement 4. Blood Cell Formation (Hemopoiesis) Blood cells are made in the liver, spleen, and bone marrow. ▪ Marrow is located in the medullary cavity, irregular spaces of spongy bone, & large canals of compact bone tissue.
5. Storage of inorganic salts Intercellular matrix of bone tissue rich in calcium salts. Calcium phosphate ▪ VITAL metabolic processes require CALCIUM. ▪ Blood clot formation ▪ Nerve impulse conduction ▪ Muscle cell contraction