An Introduction to the Body Systems

The Human Body PlanSkeletal SystemMuscular SystemIntegumentary System

Objectives

• Describe four types of tissues that make up the human body.

• Explain how tissues, organs, and organ systems are organized.

• Summarize the functions of the primary organ systems in the human body.

• Identify the five human body cavities and the organs that each contains.

Levels of Structural Organization

Chemical – atoms combine to form molecules

Cellular – molecules interact to make up cells

Tissue – cells are grouped into tissue

Organ – tissues compose organs

Organ system – organs function together to form organ systems

Organism (individual) – made up of the organ systems

Body Tissue

• All tissues are a collection of cells that have a similar structure and that work together to perform a particular function.

• Four types of body tissue:

1. Muscle tissue2. Nervous Tissue3. Epithelial Tissue4. Connective Tissue

1. Muscle Tissue– composed of cells that can contract

in a coordinated fashion.– The human body has three types of

muscle tissue: skeletal, smooth, and cardiac.• Skeletal muscle moves the bones

in your trunk, limbs, and face.• Smooth muscle handles body

functions that you cannot control consciously.

• Cardiac muscle, found in your heart, pumps blood through your body.

Chapter 45Body Tissues, continued

2. Nervous Tissue– Nervous tissue

contains cells, or neurons, that receive andtransmit messages in the form of electrical impulses.

– Neurons are nerve cells that are specialized to receive and send electrical impulses

Chapter 45Nervous Tissue, continued

– Nervous tissue can be found throughout the human body and has various functions.

• For example, nervous tissue can be found in the brain and sensory organs and is used to interpret sensory information.

Chapter 45Body Tissues, continued

3. Epithelial Tissue- tissue that is composed of a sheet of cells and that covers a body surface or lines a body cavity.

– Epithelial tissue is found in various thicknesses and arrangements, depending on where it is located.

Chapter 45Body Tissues, continued

• Epithelial Tissue, continued– Each epithelial layer

is formed from cells

that are tightly bound

together, often

providing a protective

barrier for these

surfaces.

Chapter 45Body Tissues, continued

4. Connective Tissue

is a tissue that has a lot of intracellular substance and that connects and supports other tissues.

Chapter 45Body Tissues, continued

• Connective Tissue, continued

– Connective tissues are the most abundant and diverse of the four types of tissue and contain a substance called matrix.

– Matrix is an intracellular substance that gives connective tissue its strength and flexibility and can be solid, semisolid, or liquid.

Chapter 45Human Body Tissues

Chapter 45Organs and Organ Systems

• An organ consists of various tissues that work together to carry out a specific function.

• Groups of organs interact in an organ system.

• Organ systems work together to function in an efficient, integrated manner.

Organs and Organ Systems

• Integration of Organ Systems

– An even higher level of organization is the integration of organ systems.

– The integration of organ systems can be described as each organ system having organs associated with it according to that organ’s primary function. This is so the organ system can work more efficiently.

Body Cavities

• Many organs and organ systems in the human body are housed in compartments called body cavities.

• These cavities protect internal organs from injuries and permit organs to function while remaining securely supported.

• Each human cavity can contains one or more organs.

Body Cavities continued…

– The human body has five main body cavities, including the cranial cavity, the spinal cavity, the thoracic cavity, the abdominal cavity, and the pelvic cavity.

– The cranial cavity is the cavity that contains, supports, and protects the brain.

– The spinal cavity is the cavity that contains, supports, and protects the spinal cord.

Body Cavities continued…

• The thoracic cavity is the cavity that contains, supports, and protects the heart, esophagus, and the organs of the respiratory system.

• The abdominal cavity is the cavity that contains, supports, and protects the digestive system.

• The pelvic cavity is the cavity that contains, supports, and protects the organs of the reproductive and excretory systems

Objectives: Skeletal System

• Distinguish between the axial skeleton and the appendicular skeleton.

• Explain the function and structure of bones.

• Summarize how bones develop and elongate.

• List three types of joints and give an example of each.

• Describe a common disorder that affects the skeleton

The Skeletal System

• Composed of bone, cartilage, and ligaments

• Protects and supports body organs

• Provides the framework for muscles

• Site of blood cell formation

• Stores minerals

The Skeleton

• A skeleton is the bones of a human or animal body that form the framework of the body, support the muscles and organs, and protect the inner organs.

• The variation in size and shape among the bones that make up the skeleton reflects their different roles in the body.

Subsections of the Human Skeleton

o The purple is the axial skeleton and the yellow is the appendicular skeleton.

The Skeleton Is Divided Into Two Distinct Parts:

1. The axial skeleton consists of bones that form the axis of the body and support and protect the organs of the head, neck, and trunk.

• Click on these links to read about the axial parts of the body.

• The skull• The sternum• The ribs• The backbone

The Appendicular Skeleton

2. The appendicular skeleton is composed of bones that anchor the appendages to the axial skeleton.

• Click on these links to read about the appendicular parts of the body.

• The lower body• The upper body• The shoulders• The pelvic area

• Axial skeleton– skull (cranium and facial bones)– hyoid bone (anchors tongue and muscles

associated with swallowing– vertebral column (vertebrae and disks)– thoracic cage (ribs and sternum)

• Appendicular skeleton– pectoral girdle (clavicles and scapulae)– upper limbs (arms)– pelvic girdle (coxal bones, sacrum, coccyx)– lower limbs (legs)

Bone Function and Structure

• The bones that make up the skeleton function in a variety of ways– support muscles – protect internal organs– help movement– play vital roles in important metabolic processes.

• Bones do not make up most of a body’s mass. – Being “big boned” is no excuse for being

overweight!

Types of Bones

The bones of the body fall into four general categories:

1. Long bones are longer than they are wide and work as levers. The bones of the upper and lower extremities are of this type.

2. Short bones are short, cube-shaped, and found in the wrists and ankles.

3. Flat bones have broad surfaces for protection of organs and attachment of muscles

4. Irregular bones are all others that do not fall into the previous categories. They have varied shapes, sizes, and surfaces features and include the bones of the vertebrae and a few in the skull.

Bone Function and Structure

• Long Bone Structure

– A long bone’s surface is covered by a tough membrane called the periosteum.

– Periosteum is a white, double layered membrane that covers the entire surface of bone except for the joint surfaces and is richly supplied with nerve fibers and blood vessels.

Long Bone Structure, continued

• Under the periosteum is a hard material called compact bone, and this part of the bone gives all bones their strength and rigidity.

• Compact bone is composed of cylinders made of mineral crystals and protein fibers.

• Beneath some compact bone is a network of connective tissue called spongy bone.

• Spongy bone is less dense bone tissue that has many open spaces.

Bone Function and Structure continued…

• Bone marrow is a soft tissue inside some bones that can be either red or yellow.

– The type of bone marrow present determines both its composition and function.

Bone Function and Structure continued…

• Injury and Repair

– Despite their strength, bones will crack or even break if they are subjected to certain situations or are overused.

– A crack or break is referred to as a fracture.

• A fracture is an injury in which the tissue of a bone is broken.

Bone Development

• During fetal development, some bones that were originally cartilage will slowly be replaced by actual bone. This process is called ossification.

• Humans are born with over 300 bones, but adults have about 206 bones.

Where are the 206 Bones?

• 22 bones in skull• 6 in middle ears• 1 hyoid bone• 26 in vertebral column• 25 in thoracic cage

• 4 in pectoral girdle• 60 in upper limbs• 60 in lower limbs• 2 in pelvic girdle

Bone Development

• Bone Elongation– Bones continue to grow after a person’s

birth.

– Bone elongation and growth take place near the ends of long bones in an area known as the epiphyseal plate.

• The epiphyseal plate is found at the joint ends of long bones and is composed of cartilage. This area of bone will eventually become mature bone.

Joints

• The place where two bones meet is known as a joint

• Three major kinds of joints are found in the human body– Fixed– Semimovable– Movable

Types of Joints• Fixed Joints

– A joint at which no movement occurs• Semimovable Joints

– A joint that will permit limited movement– Cartilage can be involved to help these

joints move.• Movable joint

- A joint at which a wide range of motion occurs.

– There are different types of movable joints, including hinge, ball-and-socket, pivot, saddle, and gliding.

Movable Joints

– A hinge joint allows limited movement in only one plane.

– A ball-and-socket joint is another type of

moveable joint and allows 360 degree movement in 2 planes.

– A pivot joint allows 180 degree movement in only one plane.

– A saddle joint will allow 360 degree movement in only one plane.

– A gliding joint allows bones to slide over one another.

Gliding Joint

Joint Structure

– Joint structure helps movable joints deal with the pressure and stress of everyday life.

– Joints are covered with cartilage and secrete synovial fluid to reduce friction. Joints are also connected with ligaments (hold bone to bone) and tendons (hold muscle to bone) to aid in joint movement.

– Even with all this protection a joint can still be injured.

Joints continued…

– The term arthritis is used to describe disorders that cause painful, swollen joints.

• Rheumatoid arthritis develops when the immune system begins to attack body tissues, and joints become stiff and deformed.

• Osteoarthritis is a degenerative joint disease in which the cartilage covering the surface of bone becomes thinner and rougher.

Other Links

• *Site of Anatomy Terms

• *Listen to audio recordings about the skeletal system

• *Click on any part of the skeleton and it will tell you about that part of the body

Objectives: Muscular System

• Distinguish between the three types of muscle tissues.

• Describe the structure of skeletal muscle fibers.

• Explain how skeletal muscles contract.

• Describe how muscles move bones.

• Explain the process in which a muscle becomes fatigued.

Muscular system• Composed of

muscles and tendons

• Allows manipulation of the environment, locomotion, and facial expression

• Maintains posture

• Produces heat

Muscle Types

• A muscle is an organ that can contract in a coordinated fashion and includes muscle tissue, blood vessels, nerves, and connective tissue.

• Their ability to contract and relax not only enables the body to move, but also provides the force that pushes substances, such as blood and food, through the body.

• The human body has three types of muscle tissues: skeletal, smooth, and cardiac.

Skeletal Muscle

• Skeletal muscles consciously control the moving parts of the body and are often referred to as voluntary muscles.

• Skeletal muscles are made up of muscle fibers.– Muscle fibers consist of multinucleated

elongated cells with light and dark stripes. These stripes are called striations.

Skeletal Muscle continued…

• Muscle fibers are grouped into bundles called fascicles.

• Groups of fascicles are bound together by connective tissue to form a muscle.

• The connective tissue in skeletal muscle cells can unite to form tendons.

Smooth Muscle

• Smooth muscles are spindle-shaped, have a single nucleus, and interlace to form sheets.

• Smooth muscle lacks striations, and the connective tissue that surrounds it cannot form tendons.

• Smooth muscle forms the walls of the stomach, intestines, blood vessels, and other internal organs. Because most of its movements cannot be consciously controlled, smooth muscle is referred to as involuntary muscle.

Cardiac Muscle

• Cardiac muscle makes up the walls of the heart.

• Cardiac muscle shares some characteristics with both skeletal muscle and smooth muscle.

– As with skeletal muscle, cardiac muscle tissue is striated; as with smooth muscle, it is involuntary and each cell has one nucleus.

Muscular Contractions

• Muscle contraction is an all-or-none response—either the fibers contract or they remain relaxed.

• The force of a muscle contraction is determined by the number of muscle fibers that are stimulated.– As more fibers are activated, the force of

the contraction increases.

Muscular Movement of Bones

• Muscles are attached to the outer membrane of bone, the periosteum, either directly or by a tough fibrous cord of connective tissue called a tendon.

• The point where the muscle attaches to the stationary bone is called the origin.

• The point where the muscle attaches to the moving bone is called the insertion.

Muscular Movement of Bones

• Most skeletal muscles are arranged in opposing pairs, and muscles move bones by pulling them.

• The muscle that bends a joint is known as a flexor.

• A muscle that straightens a joint is known as an extensor.

• In order for smooth movement, one muscle in a pair must contract while the opposing muscle relaxes.

Opposing Muscles in the Arm

Objectives:Integumentary System

• Describe the functions of the skin.

• Distinguish between the two layers that form skin.

• Identify two types of glands found in the skin, and describe their functions.

• Describe the structure of nails.

• Describe the structure of hair.

Layers of Skin: Epidermis and Dermis

• Epidermis– Outer layer– From the Greek epi, meaning “on” or “upon”

and derma meaning “skin”– Composed of scaly epithelial cells, top layer

mostly dead– Cells filled with the protein keratin which gives

skin a tough, leathery, waterproof quality– Skin color determined by the amount of

melanin in the lower layers of the epidermis

Layers of Skin: Epidermis and Dermis

• Dermis– The dermis is the inner layer of skin and is

composed of living cells and other specialized structures such as:

• Sensory neurons, blood vessels, muscle fibers, hair follicles, and glands

– These specialized cells help the skin protect the body as much as possible

Glands– The skin contains

exocrine glands, which are glands that release secretions through ducts.

– The main exocrine glands present in the skin are sweat glands and oil glands.

– help regulate the bodies temperature.

– Sweat glands are distributed throughout the body and release excess water, salts, and urea.

– Oil glands secret a substance called sebum.

– Sebum is an oily secretion that prevents excess water loss, softens hair and skin, and protects the body by being mildly toxic to some bacteria.

– Acne occurs when the ducts of oil glands become clogged with excessive amounts of sebum, dead cells, and bacteria.

Cross section of Skin

Hair & Nails

• Nails help protect the fingers and toes by forming nail roots under skin folds at the base and sides of the nail.

• Nails are also made primarily of keratin and rest on a bed of tissue filled with blood vessels.

• Hair protects and insulates the body and is produced by hair follicles, which are clusters of cells at the base of deep dermal pits.

• Hair is composed of keratin and is kept soft by the oil glands associated with the hair follicle.

• Hair color is the result of the presence of the pigment melanin in the hair shaft.