The Human Body An Orientation

Introductory overview of human anatomy and physiology. Covers anatomical terminology, body systems, structural organization, life functions, homeostasis, body planes, and cavities—ideal for beginners in health sciences.

Daniel Miller
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Chapter 1
The Human Body: An Orientation
Why This Matters
Learning and understanding anatomical tenninology allows you to communicate accurately with
your colleagues in the health sciences.
1.1 Form and Function of Anatomy & Physiology
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
Topics of Anatomy
Subdivisions of anatomy:
- Gross or macroscopic anatomy is the study of large, visible structures
Regional anatomy looks at all structures in a particular area of the body
H 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 surface)
Topics of Anatomy (cont.)
Subdivisions (cont.)
- Microscopic anatomy deals with structures too small to be seen by naked eye
Cytology: microscopic study of cells
Histology: microscopic study of tissues
- Developmental anatomy studies anatomical and physiological development throughout life
Embryology: study of developments before birth
To study anatomy, one must know anatomical terminology and be able to observe, manipulate,
palpate, and auscultate
Topics of Physiology
Subdivisions of physiology
- Based on organ systems (e.g., renal or cardiovascular physiology)
- Often focuses on cellular and molecular levels of the body
Looks at how the body's abilities are dependent on chemical reactions in individual cells
To study physiology, one must understand basic physical principles (e.g., electrical currents,
pressure, and movement) as well as basic chemical principles
Complementarity of Structure and Function
Anatomy and physiology are inseparable
- Function always reflects structure
- What a structure can do depends on its specific form
- Known as the principle of complementarity of structure and function
1.2 Structural Organization
Human body is very organized, from the smallest chemical level to whole organism level:
- 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
1.3 Requirements for Life
Necessary Life Functions
Maintenance of life involves:
- Maintaining boundaries
- Movement
- Responsiveness
- Digestion
Metabolism
- Excretion
- Reproduction
- Growth
Necessaiy Life Functions
Maintaining boundaries
- Separation between internal and external environments must exist
Plasma membranes separate cells
n Skin separates organism from environment
Movement
- Muscular system allows movement
Of body parts via skeletal muscles
Of substances via cardiac muscle (blood) and smooth muscle (digestion, urination)
H Contractility refers to movement at the cellular level
Necessary Life Functions (cont.)
Responsiveness
- Ability to sense and respond to stimuli
- Withdrawal reflex prevents injury
- Control of breathing rate, which must change in response to different activities
Digestion
- Breakdown of ingested foodstuffs, followed by absorption of simple molecules into blood
Necessaiy Life Functions (cont.)
U Metabolism
- All chemical reactions that occur in body cells
Sum of all catabolism (breakdown of molecules) and anabolism (synthesis of molecules)
Excretion
- Removal of wastes from metabolism and digestion
Urea (from breakdown of proteins), carbon dioxide (from metabolism), feces (unabsorbed
foods)
Necessary Life Functions (cont.)
Reproduction
- At the cellular level, reproduction involves division of cells for growth or repair
- At the organismal level, reproduction is the production of offspring
Growth
Increase in size of a body part or of organism
Necessary Life Functions (cont.)
Humans are multicellular , so to function, individual cells must be kept alive
- Organ systems are designed to service the cells
- All cells depend on organ systems to meet their survival needs
There are 11 organ systems that work together to maintain life
Survival Needs
Humans need several factors for survival that must be in the appropriate amounts; too much or
too little can be harmful:
- Nutrients
- Oxygen
- Water
- Normal body temperature
- Appropriate atmospheric pressure
Survival Needs (cont.)
Nutrients
- Chemicals for energy and cell building
Carbohydrates: major source of energy
Proteins: needed for cell building and cell chemistry
U Fats: long-term energy storage
Minerals and vitamins: involved in chemical reactions as well as for structural purposes
Oxygen
Essential for release of energy from foods
The body can survive only a few minutes without oxygen
Survival Needs (cont.)
Water
- Most abundant chemical in body; provides the watery environment needed for chemical
reactions
Also is fluid base for secretions and excretions
Normal body temperature
- If body temp falls below or goes above 37°C, rates of chemical reactions are affected
Appropriate atmospheric pressure
- Specific pressure of air is needed for adequate breathing and gas exchange in lungs
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