Introduction to human anatomy & physiology

Anatomy & physiology are what . . . exactly?

• The study of the function (physiology) and structure (anatomy) of living organisms

• The main function of an organism is to maintain homeostasis

Maintaining homeostasis; what’s that mean?

• The short answer: maintaining a constant internal state

• The long answer: the body’s use of physical and chemical processes to maintain a constant internal environment even with changing external and internal forces

• Has huge value to the organism, for example:– cellular functioning has a lot to do with enzymes &

enzymes depend on certain temperatures– membrane permeability & diffusion rates depend

on changes in the environment

Physiology (maintaining homeostasis) is. . .

• . . . fairly simple in single-celled organisms– material crosses the plasma membrane & doesn’t

have far to travel w/in the organism– the disadvantage: cell is at the mercy of the

environment; changes in temperature or pH can have great impact

• . . . more complex in multicellular organisms– most cells not in contact with external

environment; more important to them is “internal environment”

The internal environment of multicellular organisms

• Consists of extracellular fluid (ECF)– primarily water with nutrients & raw materials for

growth & development, & some cellular waste products

– fills the space between cells & bathes the cells– 1/3 of fluid in human body is this ECF (about 2 ½

gallons!)

How homeostasis works• Each physiological variable has a set point

– a target value or range to which the organism can return

– most vertebrates have set points for temperature, H2O solute balance, blood sugar levels, blood pH, & tissue O2 & CO2 concentrations

• Feedback systems influence & maintain homeostasis

Feedback systems• Negative feedback

– sensors sense a change which trigger effectors to reverse the change

– returns body to homeostasis

– ex. when body temperature rises, we sweat, & evaporation cools body

– most feedback systems work this way

• Positive feedback– deviations from normal

conditions cause an increase or acceleration of the change in the same direction

– push body away from homeostasis

– ex. blood clotting• when a blood vessel is

injured, platelets release contents which triggers other platelets to release their contents . . .

Feedback systems, cont.• Positive feedback really

part of a larger negative feedback system– when blood clotting has

stopped loss of blood, other chemical signals interrupt the positive feedback loop & stop further release of blood clotting molecules

Temperature control (thermoregulation) is a component

of homeostasis• Generating body heat

– endotherms: animals generate heat internally

– ectotherms: animals get their heat primarily from the environment

• Maintaining body temp.– homeotherms: body

temperature remains relatively constant

– heterotherms: body temperature fluctuates as environmental temperatures change

Methods of regulating body temp.• Physical methods

– insulation: blubber, fur, feathers• Behavioral methods

– movement into & out of the sun/shade; body orientation relative to sun, wind; SA:vol control

• Physiological methods– sweating, panting

• Cellular methods– brown fat produces heat rather than

ATP when broken down

Water balance (osmoregulation) is a component of homeostasis

• 4 ways to get water: – drinking it, eating foods w/ it, absorbing by osmosis, & as a

by-product of cellular respiration• 4 ways to loose water:

– urination, defecation, evaporation (panting, breathing, sweating) & osmosis

• Osmoregulation is the control of water content and the concentration of dissolved solutes that influence osmosis– organisms indirectly control water concentration by

regulating solute content (Na, Cl, K, Mg & Ca)– imbalances can lead to health problems; muscle spasms,

confusion, paralysis, death

The kidney is chief osmoregulator in humans

• Kidney maintains water balance & solute concentration in body fluids– filters blood and

reabsorbs water & other substances needed by body

– waste products & water removed from bloodstream pass to bladder & are excreted as urine

– nephron is functional unit of kidney

Form (anatomy) follows function• If a structure is adaptive (the product of natural

selection), then its physical features closely reflect its function– this is true of large animal structures & for small

molecules, organelles and cells, too– cells of multicellular organisms can specialize in structure

& function

Organization of animal bodies• Cell

– the smallest unit of organization in all organisms

• Tissue– a group of cells that

share similar structure & function

• Organ– a group of tissues that

perform specialized functions

• Organ system– a group of organs that

work together to perform one or a few related functions

Four main tissue types• Epithelial tissue

– covers & lines most surfaces of animal bodies – forms skin, & lining of the lungs, digestive tract &

blood vessels– several types

• Connective tissue– cells interspersed throughout a matrix; binds &

supports other tissues – several types; loose, fibrous, adipose, cartilage,

bone, & blood• Muscle tissue

– contractile cells; functions in movement– three types; skeletal, cardiac, & smooth

• Nervous tissue– specialized cells that send & receive electrical

signals; senses stimuli & transmits information (communication system)

– one type

Organ systems main structures & functions

• Integumentary system– skin, hair & nails– protect organism from injury, infection &

dehydration; thermoregulation• Skeletal system

– bone & cartilage– protects internal organs; provides support;

provides attachment for muscles• Muscular system

– muscles– allows for movement; produce heat

Organ systems main structures & functions continued

• Nervous system– brain, spinal cord, nerves, sense organs– coordinates body activities by sensing, interpreting &

responding to (internal & external) stimuli • Circulatory system

– heart, blood & blood vessels– transport gases, nutrients & wastes

• Lymphatic & immune system– lymph nodes & vessels, bone marrow, spleen &

thymus gland– returns excess fluid to the circulatory system &

defends the body against infections & cancer

Organ systems main structures & functions continued

• Respiratory system– nasal cavity, trachea, bronchus & lungs– gas exchange

• Digestive system– mouth, esophagus, liver, stomach, small & large intestine,

rectum, anus– ingest & break down food; absorb nutrients; eliminate

undigested material• Urinary / excretory system

– kidneys, ureters, urinary bladder, urethra– removes waste products from blood; maintains chemical

makeup, pH, & water balance of blood

Organ systems main structures & functions continued

• Reproductive system– female: ovaries, oviduct, uterus & vagina– male: testes & associated vessels, prostate

gland, urethra, penis– produces gametes & sex hormones; female

system supports growing embryo• Endocrine system

– hypothalamus, pituitary gland, thyroid gland, adrenal glands, pancreas, ovaries & testes

– secrete chemical messengers (hormones) that regulate body activities

Remember. . . • An organism contains a number of organ

systems all functioning together as an integrated, coordinated unit– Coordinated to do what?– Maintain homeostasis

• How do all these organ systems work together to do that?– primarily under the control of the nervous &

endocrine systems• electrical & chemical signals sent to direct activities

of other organ systems