The Muscular System & The Skeletal System & Skin CRCT Coach Book: Pages 72-75

For humans and most other animals, movement is important for survival. Being able to move makes it possible to escape danger, get food, and to find a mate. Movement is made possible by the skeletal and muscular systems.

The Skeletal System: Purpose: supports the body and allows movement. It also protects internal organs, stores some materials, and makes blood cells

2 Parts: Axial: Skull & vertebral column 2. Appendicular: appendages (arms, legs, hips & shoulders)

Major Organs: 206 bones (in humans) cartilage

Bones Did you know?? Bones are living tissues that make up the skeleton. Bones support the body. They are made up of bone cells surrounded by deposits of calcium and other minerals. A typical bone is surrounded by a tough layer of connective tissue. As blood passes through this layer, it supplies oxygen and nutrients to the bone

Blood Marrow Inside bones are cavities that contain a soft tissue called bone marrow. Yellow marrow is made up mostly of fat cells. Red marrow produces red blood cells, some kinds of white blood cells, and platelets.

Cartilage The skeleton of a developing fetus begins as cartilage. Cartilage is a flexible connective tissue. As the body develops, most of the cartilage in the body is replaced by bone. Some parts of the body where cartilage is not replaced by bone include the lower part of the nose and the connective tissue that forms your ears.

Cartilage continued… Cartilage also remains at joints, the places where two bones meet. This cartilage helps cushion the joints. Many long bones, such as those in the arms and legs, have growth plates at their ends. At these plates, cartilage grows, making the bones longer. After a while, the new cartilage is replaced by bone. By early adulthood, the cartilage in the growth plates is replaced by bone. When this happens, the person stops growing.

Joints A joint is a place where one bone attaches to another. Tough fibers called ligaments connect bones to each other at joints.

Types of Joints There are three main types of joints: Immovable or fixed joint Slightly movable joint Freely moveable joints Each type of joint is described by the type of movement it allows.

Immovable Joints An immovable joint, or fixed joint, does not allow movement. At this type of joint, the bones are locked together by connective tissue or fused together. The bones in the skull meet at immovable joints.

Slightly Movable Joints Slightly movable joints allow restricted movement. The joints between adjacent vertebrae that protect the spinal cord are examples of slightly movable joints.

Freely Movable Joints Freely movable joints allow movement in one or more directions. The four common types of freely movable joints are: Ball and Socket Joint Hinge Joint Pivot Joint Saddle Joint

The Muscular System Purpose: The muscular system consists of the body’s muscles. One job of the muscular system is to work with the skeletal system to move the body. It also helps to: keep the body warm give the body shape provide the force needed to move blood throughout the body.

There are about 600 muscles in the human body!! Two Main types: Involuntary: you can not control them Voluntary: you can control them

Types of Muscle There are three basic types of muscle tissue in the human body: skeletal muscle smooth muscle cardiac muscle Each type of muscle tissue plays a different role.

Skeletal Muscle Muscle tissue that connects to the bones. Most skeletal muscles are consciously controlled by the central nervous system. These muscles are used for such movements as kicking a ball, lifting a fork, or turning the pages of a book. Skeletal muscles look striped because they have bands called striations. For this reason, skeletal muscle is also called striated muscle.

Smooth Muscle A type of muscle that is usually not under your conscious, voluntary control. The stomach and the walls of veins are made up mostly of smooth muscle tissue. Smooth muscles do such things as moving food through the digestive tract. Smooth muscle cells are not striated.

Cardiac Muscle Cardiac muscle tissue makes up the heart. only in the heart. Recall that the heart is a muscular organ that pumps blood through the circulatory system. Cardiac muscle is striated, like skeletal muscle. However, cardiac muscle is not under your conscious or voluntary control. In this way, cardiac muscle is more like smooth muscle.

Bones and Muscles: Working Together Skeletal muscles are attached to the bones of the skeleton by strips of connective tissue called tendons. The muscles are attached to bones in opposing pairs. When one muscle contracts, or tightens, it pulls the bone in one direction. The other muscle in the pair relaxes. To return the bone it its original position, the second muscle contracts, pulling the bone in the opposite direction, as the first muscle relaxes.

SKIN Skin is the largest organ in the human body. Spread out, it covers 1.5 meters squared! Functions: Protection Maintain temperature Eliminate wastes Gather information Produce vitamin D

2 Layers: Epidermis Dermis Under the skin is a layer of fat

Epidermis Top layer Mostly dead skin cells Protects the under layers Thinner than the dermis No nerves or blood vessels Does contain melanin-pigment that gives skin it’s color

Dermis Thicker, underneath layer Contains: Blood vessels Nerves Sweat glands Oil glands Hair follicles