Welcome to Unit 5! The Skeletal System

Subdivisions The skeletal system is subdivided into two divisions Axial skeleton Bones that form the longitudinal axis of the body Skull, vertebral column, pelvis Appendicular skeleton Think appendages Bones of limbs The system includes Bones (206 of them in adulthood!) Joints Cartilages Ligaments

Functions Predict first! Functions Your book found 5 functions Support Protection Movement Storage Blood cell formation

Classification Classification of Bones Question: Compact bone Dense, smooth, on the outside of the bone Spongy bone Small, needle-like pieces of bone and lots of open spaces Question: What might those open spaces be helpful? Lighten the load!

Warm Up Predict: What would happen if there was too much compact bone?

Melorheostosis Causes excessive growth of compact bone

Classification Classification based on shape Long bones Short bones Flat bones Irregular bones

Classification Description Examples Long bones Longer than they are wide Mostly compact bone Femur, radius, ulna, tibia, humerus Short bones Cube-shaped Contain mostly spongy bone Wrist and ankle bones Patella Flat bones Thin, flatted, and generally curved 2 thin layers of compact bone sandwiching a spongy bone Usually protect vital organs Skull, ribs, sternum Irregular bones Catch-all category Needed for muscular attachment and protection Vertebrae and hip bones Activity: present some notes and have them categorize them?

STOP! Color the different bone shapes Draw a SQUARE around the axial skeleton and label it Draw CIRCLES around the appendicular skeleton and label it Make a table on the back with a drawing of a cross-section of long/short/flat bones that shows the compact/spongy bone

Structure of Long Bones-Outside Diaphysis: shaft, composed of compact bone Epiphysis: ends of the long bone Consists of a thin layer of compact bone enclosing an area of spongy bone Epiphyseal line: demarcation between diaphysis and epiphysis This is where your growth plate used to be

Growth Plate http://www.personal.ps u.edu/staff/m/b/mbt102/ bisci4online/bone/bone5 .htm More on this later 

Structure of Long Bones-Outside Articular cartilage: hyaline cartilage that covers the epiphysis and provides a smooth, slippery surface for smooth joint movement Periosteum: fibrous connective tissue membrane that covers and protects the diaphysis

Structure of Long Bones-Inside Inside the diaphysis, there is a medullary cavity Called “yellow marrow” Stores fat Question: Why might it be advantageous for the bones to be this way? Again, lighten the load!

Structure of Long Bones-Inside In infants, the medullary cavity used to house “red marrow’ Site of blood cell formation Marrow makes white blood cells (WBC), red blood cells (RBC), and other components In adults, blood cell formation is confined to spongy bone of flat bones and a few long bones

Leukemia http://www.youtube.com/watch?v=HP4NxUFgFrs Leuko (white) + emia (condition of the blood) = condition of the white blood cells Cancer of the blood cells that originates in the bone marrow Makes abnormal white blood cells that grow out of control Diagnosed through a bone marrow biopsy Treatment Chemotherapy Bone marrow transplant http://www.youtube.com/watch?v=HP4NxUFgFrs

Note: The surface of each bone is full of bony markings Where muscles, tendons, ligaments attach Where blood vessels and nerves pass We will be getting into this stuff after we learn more about the physiology of the bones so get excited!!! (This is the best part!)

Microscopic Anatomy-Compact Bone Has many passageways for nerves, blood vessels and route for waste disposal

Bone Formation, Growth, and Remodeling