Skeletal System Structure and Growth of Bones Organization of the Skeleton

Functions of the Skeletal System Supports the bodySupports the body Protects soft body partsProtects soft body parts Produces blood cellsProduces blood cells Stores minerals and fatStores minerals and fat Permits flexible body movementPermits flexible body movement

Tissues of the Skeletal System BoneBone –compact bone dense matrix of salts (calcium phosphate)dense matrix of salts (calcium phosphate) –spongy bone thin plates with open spacesthin plates with open spaces –bone marrow red: produces blood cellsred: produces blood cells yellow: stores fatyellow: stores fat cells = osteocytes

Tissues of the Skeletal System CartilageCartilage –hyaline firm yet flexiblefirm yet flexible at ends of long bones, ribs, in noseat ends of long bones, ribs, in nose –fibrocartilage strong for supportstrong for support in knee, disks between vertebraein knee, disks between vertebrae –elastic cartilage most flexiblemost flexible in ear flapsin ear flaps cells = chondrocytes

Tissues of the Skeletal System Fibrous connective tissueFibrous connective tissue –periosteum covers long bonescovers long bones contains blood and lymphatic vessels, nervescontains blood and lymphatic vessels, nerves –ligaments connect bone to boneconnect bone to bone –tendons connect muscles to bones at jointsconnect muscles to bones at joints cells = fibroblasts

Cells Involved in Bone Growth and Repair Osteoprogenitor cells (unspecialized, give rise to other cells) Osteoblasts (bone-forming cells) Osteocytes (mature bone cells) Monocytes (red bone marrow) Osteoclasts (bone resorption)

Bone Development and Growth Bone formation = ossificationBone formation = ossification –Bones of the skull form by Intramembranous ossification Bones develop between sheets of fibrous tissueBones develop between sheets of fibrous tissue –Most bones form by Endochondral ossification Cartilage models are formed firstCartilage models are formed first At ossification centers, cartilage is gradually replaced by boneAt ossification centers, cartilage is gradually replaced by bone

Endochondral Ossification Forms during fetal development Forms spongy bone surrounded by compact bone Band of cartilage that allows continued growth Spongy bone resorbed to form medullary cavity Formed by secondary ossification

Remodeling of Bones OsteoclastsOsteoclasts –break down bone –remove worn cells –assist in depositing calcium in the blood OsteoblastsOsteoblasts –take calcium from blood –form new bone

Bone Repair Blood clot forms in space between broken ends Fibrocartilage fills space Osteoblasts produce spongy bone Spongy bone resorbed, compact bone built on periphery

Applying Your Knowledge A.Where is red marrow located? B.Which one is a mature bone cell? C.Which one would be responsible for resorbing spongy bone as in the figure on the right? 1. Osteoblast 2. Compact bone 3. Spongy bone 4. Osteoclast 5. Osteocyte Spongy bone resorbed, compact bone built on periphery

Axial Skeleton: Midline of the Body SkullSkull Hyoid boneHyoid bone Vertebral columnVertebral column Rib cageRib cage

Bones of the Skull

The Vertebral Column

The Rib Cage

Appendicular Skeleton: Pectoral and Pelvic Girdles and the Limbs

Bones of Pectoral Girdle, Arm, Hand

Bones of Pelvic Girdle, Leg, Foot

Joints: Articulations between Bones Fibrous joints: immovableFibrous joints: immovable Cartilaginous jointsCartilaginous joints connected by hyaline or fibrocartilage cartilageconnected by hyaline or fibrocartilage cartilage slightly movableslightly movable Synovial jointsSynovial joints separate the bones by a cavityseparate the bones by a cavity freely movablefreely movable HingeHinge Ball-and-socketBall-and-socket

Knee Joint

Movements Permitted by Synovial Joints

Applying Your Knowledge A.Which vertebrae are attached to ribs? B.Which forms the “tailbone”? C.Which forms the fingers and toes? D.Which bone is in the upper leg? 1. Skull 2. Thoracic vertebrae 3. Cervical vertebrae 4. Lumbar vertebrae 5. Coccyx 1.Radius 2.Femur 3.Phalanges 4.Sternum 5.Coxal bone For A and B For C and D