Anatomy and Physiology: Body Organization

Anatomy and Physiology

• Anatomy is the study of the body's structures.
• Physiology is the study of how those structures function.
• Structure determines function, thus anatomy and physiology are studied together.
• Anatomy provides structural information.
• Physiology provides functional information.

Levels of Structural Organization

• The human body has six levels of organization: chemical, cellular, tissue, organ, system, and organismal.
• The chemical level includes atoms and molecules, such as DNA and glucose.
• Atoms combine to form molecules.
• Cells, the basic structural and functional units, constitute the cellular level.
• Tissues, groups of similar cells performing specific functions, form the tissue level.
• Epithelial, connective, muscle, and nervous are the four basic tissue types.
• Organs are composed of two or more different tissues and perform specific functions.
• The heart, lungs, and kidneys are examples of organs.
• Organ systems are groups of organs working together for a common purpose.
• The digestive, respiratory, and cardiovascular systems are examples of organ systems.
• The organismal level comprises the whole organism, the sum of all structural levels working together.

Characteristics of Life

• Living organisms share organization, metabolism, responsiveness, movement, reproduction, and growth and development.
• Organization is the interrelationship and interaction of parts to perform functions.
• Metabolism includes all chemical reactions in an organism, including anabolism (building up) and catabolism (breaking down).
• Responsiveness is the ability to detect and react to internal or external changes.
• Movement includes self-initiated movement and the transport of substances within the organism.
• Reproduction is the creation of copies, either sexually or asexually.
• Growth is an increase in size.
• Development is change in form or function over time.
• Differentiation is the specialization of cells for specific functions.

Homeostasis

• Homeostasis is the maintenance of a stable internal environment despite external changes, essential for survival.
• Homeostatic control systems have a receptor, control center, and effector.
• The receptor detects changes and sends information to the control center.
• The control center evaluates information and determines the response.
• The effector carries out the response.
• Negative feedback mechanisms are primary for maintaining homeostasis, where the response reduces the initial stimulus.
• Body temperature regulation is an example of negative feedback.
• Positive feedback mechanisms amplify the initial stimulus, leading to a greater response.
• Blood clotting exemplifies positive feedback.

Body Planes and Sections

• Anatomical position is the standard reference: body erect, facing forward, arms at sides, palms forward.
• The sagittal plane divides the body into right and left parts.
• The midsagittal (median) plane divides the body into equal right and left halves.
• The frontal (coronal) plane divides the body into anterior and posterior parts.
• The transverse (horizontal) plane divides the body into superior and inferior parts.
• An oblique section is a diagonal cut between horizontal and vertical planes.

Body Cavities

• Body cavities protect and cushion internal organs.
• The dorsal body cavity includes the cranial cavity (housing the brain) and the vertebral cavity (housing the spinal cord).
• The ventral body cavity includes the thoracic cavity and the abdominopelvic cavity.
• Pleural cavities (housing the lungs) and the mediastinum further divide the thoracic cavity.
• The mediastinum contains the heart, esophagus, and trachea.
• The abdominopelvic cavity is divided into the abdominal cavity and the pelvic cavity.
• The abdominal cavity contains the stomach, intestines, and liver.
• The pelvic cavity contains the bladder, reproductive organs, and rectum.
• Serous membranes line the ventral body cavities and cover the organs within.
• The serous membrane has parietal (lining cavity walls) and visceral (covering organs) layers.
• Serous fluid fills the space between layers, reducing friction.

Anatomical Terminology

• Superior (cranial): Toward the head or upper part; above.
• Inferior (caudal): Away from the head or toward the lower part; below.
• Anterior (ventral): Toward the front; in front of.
• Posterior (dorsal): Toward the back; behind.
• Medial: Toward the midline; on the inner side.
• Lateral: Away from the midline; on the outer side.
• Intermediate: Between medial and lateral structures.
• Proximal: Closer to the origin or attachment point.
• Distal: Farther from the origin or attachment point.
• Superficial (external): Toward the body surface.
• Deep (internal): Away from the body surface; more internal.

Integumentary System

• Consists of skin, hair, nails, and glands.
• Functions include protection, temperature regulation, sensation, and vitamin D synthesis.
• The epidermis is the outer layer of stratified squamous epithelium.
• The dermis is the inner layer of connective tissue.
• The hypodermis (subcutaneous layer), below the dermis, contains adipose tissue.
• Skin color is determined by melanin, carotene, and hemoglobin.

Skeletal System

• Consists of bones, cartilage, and ligaments.
• Functions include support, protection, movement, mineral storage, and blood cell formation.
• Bone types include long, short, flat, and irregular.
• Bone structure includes compact and spongy bone.
• Bone formation (ossification) occurs through intramembranous and endochondral ossification.
• Joints (articulations) are where two or more bones meet.
• Joint types include fibrous, cartilaginous, and synovial.

Muscular System

• Consists of skeletal, smooth, and cardiac muscle.
• Functions include movement, posture, and heat production.
• Skeletal muscle is voluntary and striated.
• Smooth muscle is involuntary and non-striated.
• Cardiac muscle is involuntary and striated.
• Muscle contraction involves the sliding filament mechanism.

Nervous System

• Consists of the brain, spinal cord, and nerves.
• Functions include communication, control, and responsiveness.
• The central nervous system (CNS) includes the brain and spinal cord.
• The peripheral nervous system (PNS) includes nerves and ganglia outside the CNS.
• Neurons are the basic functional units.
• Neurotransmitters transmit signals across synapses.

Endocrine System

• Consists of glands that secrete hormones.
• Functions include regulating growth, metabolism, and reproduction.
• Hormones are chemical messengers that travel through the bloodstream.
• Major endocrine glands include the pituitary, thyroid, adrenal, and pancreas.

Cardiovascular System

• Consists of the heart, blood vessels, and blood.
• Functions include the transport of oxygen, nutrients, hormones, and waste products.
• The heart pumps blood through the circulatory system.
• Blood vessels include arteries, veins, and capillaries.
• Blood consists of plasma and formed elements (red blood cells, white blood cells, platelets).

Lymphatic System

• Consists of lymphatic vessels, lymph nodes, and lymphoid organs.
• Functions include immunity, fluid balance, and lipid absorption.
• Lymph is a fluid similar to plasma that circulates in lymphatic vessels.
• Lymph nodes filter lymph and house immune cells.
• Lymphoid organs include the spleen, thymus, and tonsils.

Respiratory System

• Consists of the lungs, airways, and respiratory muscles.
• Functions include gas exchange (oxygen and carbon dioxide).
• Ventilation is the movement of air into and out of the lungs.
• Gas exchange occurs in the alveoli.

Digestive System

• Consists of the mouth, esophagus, stomach, intestines, liver, pancreas, and gallbladder.
• Functions include digestion, absorption, and elimination.
• Digestion is the breakdown of food into smaller molecules.
• Absorption is the movement of nutrients from the digestive tract into the bloodstream.
• Elimination is the removal of undigested waste products.

Urinary System

• Consists of the kidneys, ureters, bladder, and urethra.
• Functions include filtering blood, regulating fluid and electrolyte balance, and eliminating waste products.
• The kidneys filter blood and produce urine.
• Urine is stored in the bladder and eliminated through the urethra.

Reproductive System

• Consists of the male and female reproductive organs.
• Functions include reproduction and hormone production.
• Male reproductive organs include the testes, vas deferens, and penis.
• Female reproductive organs include the ovaries, uterus, and vagina.