A&P - 1.2 Structural Organization of the Human Body

levels of organization

1) chemical level

2) cellular level

3) tissue level

4) organ level

5) organ system level

6) organismal level

chemical level

• atoms bond to form molecules with three-dimensional structures (ex: hydrogen atoms and oxygen atom bond to form a water molecule)

• examples: water molecules, glucose, proteins, etc.

cellular level*

• a variety of molecules combine to form the fluid and organelles of a body cell

• examples: muscle cells, blood cells, nerve cells, etc.

cell

structural building block of all plants and animals, can be produced only from pre-existing cells, and are the smallest units capable of performing all vital life functions

tissue level

• a community of similar cells from a body tissue

• examples: muscle tissue, nerve tissue, connective tissue, and epithelial tissues

organ level

• two or more different tissues combine to form an organ (the type of tissues that compose the organ dictates the function of the organ)

• examples: heart, lungs, stomach, etc.

organ system level**

• two or more organs work closely together to perform the functions of a body system

organismal level

many organ systems work harmoniously together to perform the functions of an independent organism

organism

a living being that has a cellular structure and that can independently perform all physiologic functions necessary for life

integumentary system

• organs - skin, accessory structures, hair, and nails

• functions - external support, protection of body, temperature regulation, barrier for immune function

skeletal system

• organs - bones, cartilage, joints

• functions - internal support, protection of organs, flexible framework for body movement, forms blood cells, and mineral storage

muscular system

• organs - skeletal muscles, and tendons

• functions - locomotion, support, and body heat production

nervous system

• organs - brain, spinal cord, peripheral nerves

• functions - detects and processes sensory information, directs responses to that stimuli by coordinating activities of other organ systems

endocrine system

• organs - hormone secreting glands - thyroid gland, pituitary gland, adrenal gland, pineal gland, pancreas, testes and ovaries

circulatory system

• organs - heart, blood, and blood vessels

• functions - transport of nutrients to cells, and waste products from cells, homeostasis of body temperature

lymphatic and immune system

• organs - lymph nodes, lymphatic vessels, spleen, thymus gland, bone marrow, and tonsils, (immune cells)

• functions - returning extracellular fluid to the blood, houses immune cells, provides protection against infection and disease, transports lymph, absorbs and transports fats

respiratory system

• organs - lungs, trachea, larynx, and nasal passages

• functions - gas exchange (O₂ and CO₂) between air and circulating blood

digestive system

• organs - salivary glands, esophagus, stomach, small intestine, large intestine, liver, and gallbladder

• functions - intake, breakdown, and absorption of food in order to acquire nutrients, minerals, vitamins, and water, as well as the elimination of feces

urinary system

• organs - kidneys, ureters, urinary bladder, and urethra

• functions - controls water balance in the body, filters the blood to remove nitrogenous wastes, eliminates excess water, salts, and waste products, controls pH, and electrolyte balance

reproductive system (male)

• organs - testes, scrotum, prostate gland, seminal vesicles, epididymis, and penis

• functions - production and delivery of sperm (gametes), production of sex hormones

reproductive system (female)

• organs - ovaries, uterus, vagina, and mammary glands

• functions - production of egg (gamete), secretion of sex hormones, copulation, and support of fetus/infant