Skeletal and Muscular Systems Sierra Johnston, Jack Garnsey, and Morry Stein

5 teaching points The three types of muscles (smooth, skeletal, and cardiac) are found all over the body and, along with tendons, they make up the muscular system. The sliding filament theory describes how muscle contraction works. The bone's structure is made up of many parts that contribute to the functions of a bone. The five functions of the skeletal system are protecting internal organs, providing attachment surfaces for muscles, producing blood cells, storing minerals, and maintaining mineral homeostasis. Growth and development of bones are crucial to the skeletal system and how bones function.

Skeletal Muscle Attached to bones and allows them to move as well as protects them Most common and is moved voluntarily Attached to the skeleton by tendons Tendons- tough, connective tissue Each muscle consists of hundreds to thousands of skeletal muscle fibers -Fibers are bundled together and wrapped in tissue. -Tissue protects the muscle cells and allows them to contract -Tissues also provide pathways for nerves and blood cells Work hard to move body parts

Smooth Muscles Found in all internal organs Contract involuntarily to help organs perform they're functions -ex. Stomach muscles squeeze, helping break the food down

Cardiac Muscle Found specifically and only in the heart Works involuntarily Contracts to squeeze blood out of the heart Relaxes to fill the heart with blood With the help of ATP, cardiac muscle never gets tired, it works constantly without ever pausing to rest

Sliding Filament Theory Myosin filaments use “ATP” to walk along the actin filaments with their cross bridges Myosin pulls the actin filaments closer together The Z lines get pulled by the actin filaments Causes the whole sarcomere in the muscle fibers to contract This contraction then causes movement of the bone and muscle -Muscles cannot lengthen: in order to move in a different direction, the muscles work in opposition

Skeletal System Skeleton- internal framework of 206 bones in a fully grown adult Consists of bones, cartilage, and ligaments Ligament- band of fibrous, connective tissue that holds bones together and keeps them in place Bones consists of three types of bone cells and four types of tissue Bones are connected together by joints

Functions of the skeletal system Produces blood cells Keeps body upright and gives it its shape Protects internal organs from damage Provides attachment surfaces for skeletal muscles Stores minerals and maintains mineral homeostasis

Bone matrix -forms underlying rigid framework of bones (basic structure) -consists of collagen -covered by blood vessels and nerves -contains bone cells that are involved in metabolic processes

Bone Tissue Compact bone- dense outer layer and really hard Spongy bone- found inside the bone and softer, less dense and lighter than compact bone Bone marrow- connective, soft tissue that produces red blood cells and inside spongy bone Periosteum- tough membrane that protects the outer layer and surfaces of bone

Bone Cells Osteocytes- maintains bone tissue and manages the mineral homeostasis Osteoblasts- makes new bone cells and takes minerals out of the bloodstream as needed to make the bone harder (constantly growing the bone) Osteoclasts- dissolves minerals back into the bloodstream (constantly breaking the bone down)

Joints Joint- a place where 2 bones meet Immovable- doesn't allow movement because it is tightly held together by collagen Ex. The skull Movable- allows full movement because it is connected by ligaments (most common and easy to move) Ex. The shoulder - Partly movable- limited movement because it is held together by cartilage Ex. The ribs and the sternum

Ossification Ossification- process in which mineral deposits replace cartilage Everyone is born with all cartilage: overtime, ossification allows the cartilage to become bone (hard and full of minerals) By late teens/early 20s, you reach skeletal maturity, in which all cartilage has been replaced by bone and bones can't grow any longer