Chapter 16: Bones, Muscles, and Skin Pages 438 – 457 Date

The Skeletal System (pg. 440) Skeletal system = all the bones in your body 5 functions: Gives shape & support Protect internal organs Muscles R attached, allow bones 2 move Blood cells R formed in some bones Marrow = soft tissue in the center of long bones & spongy bones A lot of calcium & phosphorus are stored in bones

Bone Structure (pg. 441) Bones aren’t smooth; there R rough spots, edges, pits, & holes These areas allow for blood vessels and nerves to enter & leave bones Compact bone = hard strong layer of bone under periosteum Spongy bone = toward ends of bone, lightweight, w/ open spaces Cartilage = thick, smooth layer of tissue @ the ends of bones 2 absorb shock & reduce friction Arthritis = cartilage wears away causing friction & lots of pain

Bone Development (pg. 442) When U were a baby, your skeleton is made of cartilage & over time is replaced by osteoblasts (bone forming cells) U R born w/ 300 bones & as U grow some fuse together & as an adult U only have 206 Osteoblasts & osteoclasts (breaks down bone) constantly regulate calcium & phosphorus in your body

Bones Meet (pg. 443 - 444) Joint = place where 2 bones meet Keeps bones away from each other 2 prevent friction Ligament = band of tissue that holds bones together @ joints Immovable joint = allows little 2 no movement Movable joint = allows 4 a wide range of movement Pivot = 1 bone rotates in a ring of another (head turning) Ball-in-socket = 1 bone has a rounded end that fits into a cavity of another (shoulder) Hinge = back & forth motion (knee) Gliding = 2 bone slides over another (hand)

The Muscular System (pg. 447 - 448) Muscle = organ that can relax & contract 2 allow movement U have more than 600 muscles in your body Voluntary muscles = muscles U can control Involuntary muscles = muscles U cannot consciously control

Types of Muscle Tissue (pg. 450 - 451) Skeletal muscles = muscles that move bone Tendons = thick bands of tissue that attach muscles to bone These R voluntary, the most abundant, & look striated Smooth muscles = non-striated, involuntary that move many internal organs Cardiac muscles = only in the heart, involuntary, look striated

Muscles at Work (pg. 451) Muscles work in pairs  one contracts while the other relaxes Muscles always pull not push in order to move bones This happens because of the energy in glucose

Skin (pg. 455 - 456) Skin is the largest body organ Epidermis = surface of the skin, top is dead cells New cells R formed @ the bottom of epidermis Melanin = pigment that gives skin color UV rays allow for more melanin to produce Dermis = thick layer of tissue under epidermis Blood vessels, nerves, & oil & sweat glands are here Fat is stored under dermis

Pimples Pimples occur when there is an increase in oil production (from hormones) Oil combines w/ dead skin cells 2 clog hair follicles resulting in a pimple Everyone gets pimples, especially in teenage years The amount & severity usually depend on when puberty sets in (hormones) and heredity

Functions of the Skin (pg. 456) Function are: Forms a protective covering 2 prevent injury & disease Prevents excess water loss Serves as a sensory organ Forms vitamin D, which helps absorb calcium, & produce from UV rays Regulate body temp Blood vessels constrict or expand to release or hold heat Dermis has about 3 million sweat glands, which cool the body when sweat evaporates Excrete wastes Sweat glands release water, salt, & urea

All Done!