The Human Body: An Orientation

Chapter 1

Anatomy

study of the structure of body parts and their relationship to one another

Physiology

study of the function of body parts; how they work to carry out life-sustaining activities

Macroscopic (Gross) Anatomy

study of large, visible structures

• regional anatomy

• system anatomy

• surface anatomy

Regional Anatomy

looks at all structures in a particular area of the body

System Anatomy

looks at just one system (cardiovascular, nervous, muscular, etc)

Surface Anatomy

looks at internal structures as they relate to overlying skin (visible muscle masses or veins seen on the surface)

Microscopic Anatomy

deals with structures too small to be seen by naked eye

• cytology

• histology

Cytology

microscopic study of cells

Histology

microscopic study of tissues

Developmental Anatomy

Studies anatomical and physiological development throughout life

• embryology

embryology

study of developments before birth

Chemical level

atoms, molecules, and organelles

Cellular level

single cell

Tissue level

groups of similar cells

organ level

contains two or more types of tissues

organ system level

organs that work closely together

organismal level

all organ systems combined to make the whole organism

Maintaining Boundaries

Requirements for Life

A separation between internal and external environments must exist

• plasma membranes separate cells

• Skin separates the organism from the environment

Movement

Requirements for Life

The muscular system allows movement

• of body parts via skeletal muscles

• of substances via cardiac muscle (blood) and smooth muscle (digestion, urination)

Contractility

refers to movement at the cellular level

Responsiveness

Requirements for Life

Ability to sense and respond to stimuli

• withdrawal reflex prevents injury

• control of breathing rate, which must change in response to different activities

Digestion

Requirements for Life

Breakdown of ingested foodstuffs, followed by absorption of simple molecules into blood

Metabolism

Requirements for Life

All chemical reactions that occur in body cells

• sum of all catabolism (breakdown of molecules) and anabolism (synthesis of molecules)

Excretion

Requirements for Life

Removal of wastes from metabolism and digestion

• urea (from breakdown of proteins), carbon dioxide (from metabolism), feces (unabsorbed foods)

Reproduction

Requirements for Life

At the cellular level, reproduction involves the division of cells for growth or repair

At the organismal level, reproduction is the production of offspring

Growth

Requirements for Life

increase in size of a body part or of an organism

Integumentary System

forms the external body covering, and protects deeper tissues from injury. Synthesizes vitamin D, and houses cutaneous (pain, pressure, etc.) receptors, and sweat and oil glands

Skeletal System

Protects and supports body organs, and provides a framework the muscles use to cause movements. Blood cells are formed within bones. Bones store minerals

Muscular System

Allows manipulation of the environment, locomotion, and facial expression. Maintains posture and produces heat.

Nervous System

As the fast-acting control system of the body, it responds to internal and external changes by activating appropriate muscles and glands

Endocrine System

Glands secrete hormones that regulate processes such as growth, reproduction, and nutrient use (metabolism) by body cells.

Cardiovascular System

Blood vessels transport blood, which carries oxygen, carbon dioxide, nutrients, wastes, etc. The heart pumps blood.

Lymphatic System/Immunity

picks up fluid leaked from blood vessels and returns it to the blood. Disposes of debris in the lymphatic stream. Houses white blood cells (lymphocytes) involved in immunity. The immune response mounts an attack against foreign substances within the body.

Respiratory System

keeps blood constantly supplied with oxygen and removes carbon dioxide. These exchanges occur through the walls of the air sacs of the lungs

Digestive System

Breaks down food into absorbable units that enter the blood for distribution to body cells. Indigestible foodstuffs are eliminated as feces

Urinary System

Eliminates nitrogenous wastes from the body. Regulates water, electrolyte, and acid-base balance of the body

male reproductive system

The overall function is the production of offspring. Testes produce sperm and male sex hormones, and male ducts and glands aid in the delivery of sperm to the female reproductive tract.

female reproductive system

The overall function is the production of offspring. Ovaries produce eggs and female sex hormones. The remaining female structures serve as sites for fertilization and development of the fetus. The mammary glands of female breasts produce milk to nourish the newborn

Nutrients

Survival needs

chemicals for energy and cell building

• carbohydrates

• proteins

• fats

• minerals and vitamins

carbohydrates

major source of energy

Proteins

needed for cell building and cell chemistry

fats

long-term energy storage

minerals and vitamins

involved in chemical reactions as well as for structural purposes

oxygen

survival needs

essential for the release of energy from foods

• The body can survive only a few minutes without oxygen

water

survival needs

most abundant chemical in the body; provides the watery environment needed for chemical reactions

• also is a fluid base for secretions and excretions

normal body temperature

survival needs

if body temp falls below or goes above 37*C, rates of chemical reactions are affected

Appropriate atmospheric pressure

survival needs

Specific pressures of air are needed for adequate breathing and gas exchange in the lungs

Homeostasis

is the maintenance of relatively stable internal conditions despite continuous change in the environment

• dynamic state of equilibrium, always readjusting as needed

• maintained by contributions of all organ systems

Receptor

homeostatic controls

sensor

• monitors environment

• responds to stimuli (things that cause changes in controlled variables)

Control Center

homeostatic controls

• determines the set point at which the variable is maintained

• receives input from the receptor

• determines appropriate response

Effector

homeostatic controls

• receives output from the control center

• provides the means to respond

• response either reduces stimulus (negative feedback) or enhances stimulus (positive feedback)

Negative Feedback

homeostatic controls

• most-used feedback mechanism in the body

• response reduces or shuts off the original stimulus

  • variable changes in opposite direction of initial change

  • ex: regulation of body temp (a nervous system mechanism), regulation of blood in glucose by insulin (an endocrine system mechanism)

Positive feedback

homeostatic controls

• response enhances or exaggerates the original stimulus

• may exhibit a cascade or amplifying effect as feedback causes the variable to continue in the same direction as the initial change

• usually controls infrequent events that do not require continuous adjustment, for example:

  • enhancement of labor contractions by oxytocin

  • platelet plug formation and blood clotting

Homeostatic Imbalance

disturbances increase the risk of disease, contribute to changes associated with aging

• control systems become less efficient

If negative feedback mechanisms become overwhelmed, destructive positive feedback mechanisms may take over

• heart failure