KEY CONCEPT The skeletal system includes bones and tissues that are important for supporting, protecting, and moving your body.

Human Skeletal System Functions Framework and support Protection Storage of minerals such as calcium Movement Production of blood cells (bone marrow) Human Skeletal System The skeleton forms a sturdy internal framework of 206 bones and associated tissues – cartilage, tendons, and ligaments. Bones provide the base to which muscles attach and also the leverage required to accomplish external movement. The skeleton protects vital organs such as the brain, spinal cord, heart and lungs. As a living, dynamic tissue, bone stores vitamins and minerals (especially calcium and phosphorus) and houses red bone marrow, which produces blood cells. Anatomists divide the skeleton into two parts, axial and appendicular. The axial skeleton (upright, or core of the body) includes the skull, ribs, sternum and vertebral column. Comprised of the shoulders, arms, hips and legs, the appendicular skeleton forms the appendages that attach to the axial skeleton. Approximately four times as strong as concrete, bone is one of the strongest materials produced by nature. It is a connective tissue composed of cells called osteocytes, which are embedded in a hard, calcified matrix. Bones are made of a dense outer layer of compact material that surrounds a core of loosely structured spongy bone. The compact layer of bone is covered by a fibrous membrane called the periosteum. Cavities within each bone contain red bone marrow (blood-forming tissue) or yellow bone marrow (fat storage). Movement of the skeleton occurs at the joints where two or more bones meet. There are three categories of joints. Slightly movable joints allow some movement but function mainly as a cushion (eg, joints between the vertebra). Freely movable, or synovial, joints allow a range of movement determined by the structure of the joint. Examples of movable joints are the ball and socket (shoulder), hinge (elbow), pivot (between radius, ulna and humerus), and saddle joint (thumb). A few joints found in the skull are non-movable (sutures). Ligaments are inelastic connective tissues which hold bones together in a joint. References Campbell, N. E., & Reece, J. B. (2002). Biology (6th ed.). San Francisco: Benjamin Cummings. Raven, P. H., & Johnson, G. B. (2002). Biology (6th ed.). McGraw-Hill. Image Reference LifeART. (1998). Super Anatomy Collection 1-9. Baltimore, MD: Williams & Wilkins, All rights reserved.

Human Skeletal System The axial skeleton is the central part of the skeleton used to protect vital organs such as the brain, heart, and lungs. The appendicular skeleton is used for movement and includes the pectoral and pelvic girdle and the extremities attached to them.

The axial skeleton includes the skull, rib cage, and spinal column. supports body and protects tissues allows for limited movement skull rib breastbone vertebra

The appendicular skeleton includes legs, arms, feet and hands. allows for movement includes bones called girdles that connect limbs to body

Cartilage is connective tissue between bones. cushions bones allows for smooth movement connect two bones cartilage

Ligaments are long bands of tissue that connect bones across a joint.

Bones connect to form joints. Joints are places were two bones meet. There are three types of joints. cartilaginous, which allows partial movement cartillage

Bones connect to form joints. Joints are places were two bones meet. There are three types of joints. fibrous, which does not allow for movement fibrous joint

Bones connect to form joints. Joints are places were two bones meet. There are three types of joints. synovial, which allows for greater movement

There are several types of synovial joints. gliding pivot ball-and-socket saddle hinge GLIDING JOINT PIVOT JOINT BALL-AND-SOCKET JOINT SADDLE JOINT HINGE JOINT

Bones are living tissue. Bone is made of compact bone tissue and spongy bone tissue. Compact bone Spongy bone

Compact bone is hard and dense. Osteocytes (bone cells) maintain compact bone rings. Haversian canals allow blood vessels in the bone. blood vessel osteocytes Haversian canals

Spongy bone protects red or yellow bone marrow. Red bone marrow produces blood cells. Yellow bone marrow is mostly fat. Periosteum A layer of connective tissue that covers bone Red bone marrow

Calcification is the process of building hard bone. combines collagen and calcium phosphate transforms cartilage into hard bone during childhood osteocyte compact bone

KEY CONCEPT Muscles are tissues that can contract, enabling movement.

Humans have three types of muscle. The muscular system moves substances throughout the body. bones of the skeletal system food through digestive system blood through circulatory system fluids through excretory system

There are three types of muscle tissue. skeletal muscle smooth muscle cardiac muscle SKELETAL MUSCLE SMOOTH MUSCLE CARDIAC MUSCLE

Skeletal muscle attaches to the skeleton by tendons. Tendons connect muscle to bone. Skeletal muscles are mostly voluntary. SKELETAL MUSCLE

Smooth muscle lines organs and is involuntary. move food through digestive organs empty liquid from the bladder control width of blood vessels Smooth muscle around this artery allows the artery to regulate blood flow by shrinking and expanding. SMOOTH MUSCLE

Cardiac muscle is found only in the heart. pumps blood throughout body controlled by pacemaker contains more mitochondria than skeletal muscle cells CARDIAC MUSCLE

“Most Skeletal Muscles Work in Opposing Pairs When one muscle contracts, the other relaxes

KEY CONCEPT The integumentary system has many tissues that protect the body.

The integumentary system helps maintain homeostasis. The integumentary system consists of many parts. skin hair nails oil glands sweat glands proteins, such as keratin (nails)

The integumentary system consists of many different tissues. The outermost layer of the skin is the epidermis. dead skin cells oils pores epidermis pore

Cells in the epidermis produce keratin and melanin. Keratin makes cells waterproof and tough feeling. Melanin is a dark pigment that absorbs UV rays.

The dermis contains most of the tissues in the skin. sweat glands oil glands pressure receptors blood vessels hair follicles dermis hair follicle oil gland pressure receptors sweat gland

A hair follicle is pit of cells that produces hair. The dermis also produces elastin and collagen. Elastin makes skin flexible. Collagen gives skin its shape.

Beneath the dermis is a layer of fat. fat layer