Chapter 1 – The Human Body
An Overview of Anatomy and Physiology
anatomy – the study of the structure of body parts and their relationships to one another
physiology – the function of the body and how the parts work
subdivisions of anatomy:
1. gross (macroscopic) anatomy is the study of large body structures visible to the naked eye
- regional anatomy – study of all structures in on particular part of the body at the same time
(bones, muscles, nerves, blood vessels, etc. in the leg)
- systemic anatomy – study of the body by system
(nervous system, skeletal system, digestive system, etc.)
- surface anatomy – study of internal body structures as they relate to the overlying skin surface
(bulging muscles, feeling a pulse in a blood vessel, etc.)
2. microscopic anatomy is the study of structures too small to be seen without a microscope
- cytology – study of cellular anatomy
- histology – study of tissue anatomy
3. developmental anatomy is the study of structural changes in an individual
- embryology – study of changes that occur before birth
other highly specialized forms of anatomy used for medical diagnosis and/or scientific research
1. pathological anatomy – gross/microscopic structural changes that occur as a result of disease
2. radiographic anatomy – internal structures (bones/tumors) based on xray/scanning procedures
3. molecular biology – structure of biological molecules (especially on a subcellular level)
3 important tools to study anatomy are observation, manipulation, and a mastery of medical terminology
- observing how the parts of the knee joint fit together
- manipulating the joint to determine a range of motion
- using anatomical terminology to name parts and describe how they are related
subdivisions of physiology are based on the operation of specific organ systems
- renal (urine production and kidney function)
- neuro (function of the nervous system)
- cardiovascular (heart/blood vessel functions)
physiology often focuses on cellular/molecular levels because the body depends on the successful functioning
of individual cells which in turn ultimately depends on the chemical reactions occurring inside each cell
physiology also deals with understanding physics
- electrical charges are responsible for all nervous/muscular system functions)
Principle of Complementarity of Structure and Function
- what a structure can do depends on its specific form
- bones support because of their hard mineral deposits
- blood flows in one direction thru the heart because valves prevent backflow
- lungs are the site of gas exchange because air sacs are moist and thin-walled
Levels of Structural Organization
simplest to most complex:
1. chemical level
atoms build molecules like water, sugar, and protein which in turn form organelles
2. cellular level
cells are the smallest unit of living things and are formed by organelles (vary in size/shape/function)
3. tissue level
tissues are groups of cells that have a common function and a characteristic role in the body
- epithelium (covers the body surface and lines the cavities)
- muscle (provides movement)
- connective (supports the body and protects organs)
- nervous (provides rapid internal communication)
4. organ level
organs are composed of at least 2 different tissue types (4 is the most common)
provides a specific function for the body
sometimes extremely complex
a single bone or a single muscle are considered as individual organs
stomach has several tissues
epithelium – lining/glands
muscle – churning/mixing
connective – supports the muscle
nervous – stimulates digestive activity
5. organ system level
composed of organs that work closely with one another to accomplish a common purpose
digestive system is the mouth, salivary glands, esophagus, stomach, pancreas, liver, gall bladder,
small intestine, large intestine, and rectum
(know Figure 1.2)
6. organismal level
highest level of organization in an individual
sum total of all structural levels working in unison
Maintaining Life
in order to maintain necessary life functions, organ systems must work together and cooperatively
8 major functional processes:
1. maintaining boundaries
- the internal environment must remain distinct and protected from the external environment
- integument keeps us from drying out & keeps harmful things out (bacteria, viruses, radiation)
2. movement
- includes all activities of the muscular system used for propulsion (walking, swimming, running)
- involves involuntary actions like peristalsis (movement of foodstuff and waste thru the body)
3. responsiveness/irritability
- ability to sense environmental changes (stimuli) & respond to them with the nervous system
4. digestion
- the process of breaking down ingested foodstuffs into simple molecules (the digestive system)
- includes molecular absorption into the blood & transportation to cells (cardiovascular system)
5. metabolism
- includes all chemical reactions that occur in the body
digestive system (breaking down food molecules into simpler compounds)
respiratory system (supplying O2 to change simpler compounds into energy molecules)
circulatory system (moves O2 and nutrients to all cells)
6. excretion
- the process of removing waste from the body
digestive system (solid/indigestible food)
urinary system (liquid nitrogenous waste like urea and uric acid)
respiratory/circulatory systems (moving gaseous CO2 to the lungs for exhalation)
7. reproduction
- occurs at both cellular level (mitosis) and organismal level (reproductive/endocrine systems)
8. growth
- an increase in the size of an organism usually accomplished by increasing the number of cells
Survival Needs
factors required in appropriate amounts in order to survive (deficits/excesses may be harmful):
1. nutrients
- taken in thru the diet and responsible for energy and cell building
- carbohydrates (sugars/starch from plants, glycogen from animals/major source of energy)
- protein (from animals, grains, and some vegetables/building cellular structures)
- fats (from animals and plants/cushions organs, insulation for the body, good source of energy)
- vitamins/minerals (required for chemical reactions)
2. oxygen
- required for chemical reactions to make ATP and to release energy in cells
- provided by the respiratory and cardiovascular systems
3. water
- obtained by ingestion and lost by evaporation/excretion
- accounts for 60% to 80% of body weight
- single most abundant chemical substance in the body
- provides the environment needed for chemical reactions to occur
- fluid base for secretions and excretions
4. normal body temperature of 98.7⁰F (37⁰C)
- if below, metabolic reactions slow and eventually stop
- if above, metabolic reactions speed to an unmanageable pace, proteins lose shape/function
- either extreme leads to death
5. atmospheric pressure
- force that air exerts on the body
- needs to remain stable for breathing/gas exchange in the lungs
- high altitudes have lower air pressure and gas exchange is too low to support metabolism
Homeostasis
the ability of the body to keep internal conditions in a dynamic state of equilibrium(balance) even tho the
outside world is continually changing
occurring when the body’s needs are met and it is functioning smoothly
almost every organ system plays a part in maintaining homeostasis (chemical, neural, or thermal)
keeping the body in equilibrium is difficult and complicated
examples:
-keeping adequate nutrient levels in the blood
- heart activity
- blood pressure
- removal of waste (solid, liquid, and gas)
- controlling body temperature
communication is essential and is in the form of electrical impulses/hormones (nervous/endocrine systems)
all homeostatic control mechanisms have at least 3 interdependent components:
1. receptor
a sensor that responds to changes in the environment
sends the input to the control center via the afferent pathway
2. control center
determines the functioning range of the variable
3. effector
the output (response) to the stimulus which is used to influence the stimulus
goes thru the efferent pathway
negative feedback –
response is to depress the stimulus and shut off the whole control mechanism
positive feedback –
response enhances the stimulus and makes the reaction occur at a faster rate
Negative Feedback
most homeostatic control mechanisms
net effect is that the output of the system shuts off the original stimulus or reduces the intensity
the variable changes in a direction opposite (negative) to the initial change (returns to the ideal value)
examples:
- regulation of body temperature
- withdrawal reflex
- control of blood glucose levels with insulin and glucagon
Positive Feedback
rarely utilized because of the tendency to race out of control
net effect is to enhance/exaggerate the original stimulus so the activity (output) is accelerated
the variable changes in the same direction as the initial disturbance
causes more deviation from the original value
controls infrequent events that do not need continuous adjustment
sets off a series of events that are self-perpetuating and explosive
examples:
- blood clotting
- childbirth
homeostatic imbalances disrupt the efficiency of organs and their control systems
- especially noticeable with increasing age
- cause of many diseases because the usual negative feedback mechanisms fail and are
replaced by positive feedback mechanisms (heart failure)
The Language of Anatomy
(know Figures 1.4, 1.5, 1.6, 1.7 and Table 1.1)
anatomical position is standing erect, feet together, arms at side, palms forward, and thumbs out
EVERY TIME A DESCRIPTION IS GIVEN
IT IS ASSUMED THE BODY IS IN THIS POSITION,
REGARDLESS OF ITS ACTUAL POSITION
orientation and directional terms:
superior (cranial) – toward the head, above
inferior (caudal) – away from the head, below
anterior (ventral) – toward the front
posterior (dorsal) – toward the back
medial – toward the midline
lateral – away from the midline
intermediate – between a medial and lateral structure
proximal – closer to the point of attachment
distal – away from the point of attachment
superficial – toward the body surface
deep – away from the body surface
directional terms allow proper explanations of body structure as they relate to one another
- the ears are lateral to the nose
- the knee is distal to the thigh
- the skin is superficial and the fibula is deep to the gastrocnemius
2 divisions of the body
- axial – head, neck, and trunk (the main axis of the body)
- appendicular – appendages/limbs attached to the main axis
3 planes of the body
- sagittal – vertical plane that divides the body into left and right sides
*midsagittal (medial) plane lies exactly in the body’s midline
*parasagittal plane is offset from the midline
- frontal (coronal)- vertical plane that divides the body into anterior and posterior sides
- transverse (horizontal/cross) – plane that divides the body into inferior and superior parts
**an oblique section is a cut made diagonally between horizontal and vertical planes
body cavities:
dorsal –
*protected by hard bony walls
*cranial cavity encases the brain
*vertebral (spinal) cavity encloses the spinal cord
ventral –
*contains the internal organs (viscera)
*thoracic cavity
- surrounded by ribs, chest muscles, and diaphragm
- pleural cavities:
lateral and each surrounds a lung
- mediastinum:
pericardial cavity surrounds the heart
superior cavity surrounds other thoracic organs (esophagus, trachea, larynx, etc.)
*abdominopelvic cavity
- inferior to the diaphragm and surrounded by muscle, not bone (except backbone)
- abdominal cavity (the most superior):
stomach, intestines, spleen, liver, etc.
- pelvic cavity ( the most inferior):
bladder, anal canal, rectum, reproductive organs
abdominopelvic cavity - can be divided into 4 quadrants:
left/right upper AND left/right lower
abdominopelvic cavity - USUALLY divided in 9 regions (2 transverse /2 parasagittal planes) centered over navel
(tic-tac-toe grid – easiest to start with navel)
- umbilical region surrounds the navel
- left and right lumbar regions immediately lateral
- epigastric (“above-stomach”) region is superior to the umbilical
- left and right hypochondriac (“below-cartilage” refers being inferior to the ribs) immediately lateral
- hypogastric (“below stomach”) region is inferior to the umbilical
- left and right iliac (superior part of hip) regions immediately lateral
other body cavities:
oral cavity – mouth that contains the teeth and tongue, continuous with remaining digestive organs
nasal cavity – within/posterior to the nose, a part of the respiratory system passageways
orbital cavities (orbits) – contain the eyes and holds them in place
middle ear cavities – within the temporal bone, medial to the eardrum, contains bones responsible for
transmitting sound vibrations to the inner ear
synovial cavities (joints) – fibrous capsules surrounding free joints (elbow, knee, shoulder, etc.)
filled with fluid to reduce friction between opposing bones
membranes in the ventral body cavity are serous membranes (serosa)
thin but double-layered
named for the specific cavity and organ with which they are associated
parietal serosa covers the walls of the cavity
- parietal pericardium lines the pericardial cavity
- parietal pleura lines the pleural cavity
- parietal peritoneum lines the abdominopelvic cavity
visceral serosa covers the outer surfaces of the organs (formed by infolding of the parietal serosa)
- visceral pericardium covers the heart
- visceral pleura covers the lung
- visceral peritoneum covers organs in the abdominopelvic cavity
serous fluid lubricates the area between the 2 membranes and between the membrane and
enclosed organ to reduce friction