The study of the human body The Skin-coverings The skeletal system-support The muscular system-movement

Structure fits function The structure of living organisms is organized in a series of hierarchical levels Atoms Molecules Cells Tissue –group of the same cells doing a specific job-muscle tissue Organ-two or more tissues working together for a specific job- heart Organ system- different organs working together- digestive system Organism- a living thing

Structure fits function

Four basic tissues In almost all animals, most of the cells of the body are organized into tissues 4 main types Epithelial- covers the body and lines organs and cavities Skin-sheets of tightly packed cells Connective-binds and supports other tissues Ligaments, tendons, bones, cartilage, blood, fat Muscle-movement Skeletal, smooth-walls of internal organs, cardiac Nervous-communication Neurons, supporting cells

Organs working together make up Organ systems The organs of humans and most other animals are organized into organ systems Teams of organs that work together to perform vital body functions Each organ system is coordinated to work together for the survival of the organism Anatomy- study of the structure of the organs in organisms Physiology- study of the function of the organs in organisms

Organ systems of the body Integumentary system- skin, hair, nails, oil and sweat glands Skeletal system-support body and anchors muscles Muscular system- moves the body

Organ systems of the body Digestive system-breaks down food and absorbs nutrients Circulatory system- transports substances throughout body Respiratory system- exchanges O2 and CO2 between blood and air Urinary system- rids body of cellular wastes Nervous system- processes sensory information and controls responses Immune and Lymphatic system-defends against disease

Organ systems of the body Endocrine system-secretes hormones that regulate the body Reproductive system- produces gametes and offspring

The Skin- integument coverings of the body Our skin is divided into two main layers Outer epidermis-composed of about 20 layers of dead cells Purpose is to provide mechanical barrier from microbes, and is a waterproof protective cover Protein keratin deposited into cells & makes it waterproof- same protein makes up our hair, nails Dermis- living layer under the epidermis Elastic and dense fibers-allow stretching Blood, nerves –temp & pain sensations Fat storage- insulation, protection of organs

The skin

The skin Our body continuously renews the cells of the epidermis, shedding old cells and growing new ones-about every 2 weeks Such turnover requires rapid cell division increasing the risk of an error-resulting in cancer Compared to other body parts, our skin is exposed to many carcinogens- cancer causing substances- UV light, smoke in lungs Consequently-80% of all cancers-(skin, lung, breast) come from epithelial tissue

Some examples of organs lined with epithelial tissue: Figure 21.3-3 Some examples of organs lined with epithelial tissue: Heart Lung Stomach Small intestine Epithelial cells Large intestine Epithelial tissue lining esophagus Urinary bladder Figure 21.3 Epithelial tissue (step 3) Epithelial tissue lining small intestine

The skeletal system Composed of bones, ligaments, tendons, cartilage- all made of Connective tissue-lots of protein fibers in a semi-solid or solid foundation. Designed to hold together or support other tissues Bones support the muscles which move the skeleton Ligaments connect bones together Tendons hold muscles to bones Cartilage acts as a cushion between bones Functions of the skeleton Support and shape Protection of organs Attachment of muscles Blood cell production-marrow Mineral storage

(a) Loose connective tissue (d) Fibrous connective tissue Figure 21.4 (a) Loose connective tissue (b) Adipose tissue (c) Blood Figure 21.4 Types of connective tissue (d) Fibrous connective tissue (f) Bone (e) Cartilage

Skeletal system The skeleton is divided into two main regions The axial skeleton is composed of: Skull bones Vertebrae Rib cage The appendicular skeleton is composed of: Bones of shoulder and arm Bones of hips and legs

Joints of the body Joints are categorized by the amount of movement that is created No movement- skull bones Slight movement- ribs, vertebrae A lot of movement- most joints- joined by ligaments and surrounded by synovial fluid “oil” Knee, shoulder, neck, hands, feet

Muscular system Muscle makes up most of the tissue in an animal’s body has specialized proteins arranged into a structure that contracts when stimulated by a signal from a nerve. Functions include: Movement- of skeleton, organs, and heart Maintain an upright posture Maintain an internal temperature Three main types of muscle tissue Striated- also called skeletal muscle- striped in appearance lines the skeleton and moves the bones using tendons

Striated muscle

Striated muscle attached to bones by tendons, responsible for voluntary movements, and striated because the contractile proteins form a banded pattern. The contractile proteins are called actin and myosin threads that make up a muscle cell (fiber) Actin are thin threads Myosin are thick threads The overlapping of the threads is responsible for the striations that contract causing movement Nerves stimulate muscles, muscles contract

Sliding filament theory of muscle contraction Each muscle cell (called a sarcomere) is composed of alternating light thin actin filaments & dark thick myosin filaments. When stimulated by a nerve, ATP energy binds to a myosin head causing it to attach to an actin binding site which pulls the actin threads towards the center causing a contraction of the muscle. Working or exercising muscles increases the size of each cell not the number of cells. When muscles do work, heat is produced which helps maintain internal body temp.

Actin and myosin threads

Cardiac muscle found only in heart tissue, composed of cells that are branched and striated, involuntary, and responsible for the contraction of the heart Intercalated discs are junctions between heart cells that act to coordinate all the cells to work together making the heart an efficient pump

(b) Cardiac muscle Junction between two cells- intercalated disks Figure 21.5b Junction between two cells- intercalated disks Muscle fiber Nucleus Figure 21.5 Three types of muscle tissue (part 2) (b) Cardiac muscle

Smooth muscle named for its lack of obvious stripes, found in the walls of various organs such as intestines and blood vessels, and involuntary.