The Human Body:

An Orientation

Anatomy is the study of the form, or structure, of body parts and how these parts relate to each other.

Physiology concerns how the parts of the body work and carry out their life-sustaining activities.

Topics of Anatomy

Gross anatomy: study of large structures; ex. heart or lung

Regional Anatomy: study of the various structures in one particular region, such as the abdomen

Systemic Anatomy: study system by system

Topics of Anatomy

Microscopic Anatomy: studies the structure to small to be seen without the aid of the microscope

Cytology: study of the cells

Histology: study of the tissues

Topics of Anatomy

Developmental Anatomy: studies the structural changes that occur from conception through old age

Embryology: studies developmental changes that occur from conception till birth

Pathological Anatomy: study of diseased body structures

The most important tools for studying anatomy are:

1. Observation

2. Manipulation

3. Mastery of anatomical terminology

Topics of Physiology

Renal Physiology: studies urine production and kidney function

Topics of Physiology

Neurophysiology:

Studies the working of the nervous system

Topics of Physiology

Cardiac physiology: studies the operation of the heart

What a structure is capable of doing depends critically on its specific architecture. This principle is called the “Principle of Complementarity of Structure and Function.”

Characteristics of Human Life

1. Responsiveness permits an organism to sense, monitor, and respond to changes in its internal or external environment.

2. Conductivity is the capacity of living cells and tissues to selectively transmit or propagate a wave of excitation from one point to another within the body.

3. Growth occurs as a result of the normal increase in the size and number of cells.

Characteristics of Human Life4. Respiration involves processes that result in

the absorption, transport, utilization, and exchange of the respiratory gases.a. Internal respiration occurs between the blood and the body cells.b. External respiration occurs between te blood and the air in the lungs

5. Digestion is the process of breaking down food into simple substances that can be absorbed and used by body cells.

Characteristics of Human Life

6. Absorption refers to the movement of digested nutrients through the wall of the digestive tube and into the body fluids for transport to cells.

7. Secretion is the production and delivery of specialized substances for diverse body functions.

8. Excretion refers to the removal of waste produced during many body functions.

Characteristics of Human Life

9. Circulation refers to the movement of body fluids and many other substances from one body area to another.

10. Reproduction involves the formation of a new individual and also the formation of new cells in the body to permit growth, wound repair, and replacement of dead or aging cells.

What term best describes the above physical and chemical reactions occurring in the body?

Survival Needs

1. Nutrition

2. Oxygen

3. Water

4. Maintained body Temperature

5. Atmospheric Pressure

Which need given some time does the body compensate for?

Levels of Organization

1. Chemical: atoms form molecules2. Organelle: tiny organ within a cell3. Cellular: basic unit of life4. Tissue: group of cells that perform a specific

function5. Organ: group of tissues that perform a specific

function6. System: group of organs that perform a specific

function7. Organism: Human

The Language of Anatomy

Anatomical position: the body is erect and the arms are hanging at the sides of the body with the palms forward and the thumbs pointed away from the body

The Language of Anatomy

Directional terms: where one body structure is in relation to another

Regional terms: designates specific area of the body

The Language of Anatomy

Within the axial (vertical axis) portion of the body are two major closed body cavities that contain the internal organs:

Dorsal Body Cavity

Ventral Body Cavity

Dorsal Body CavityCranial cavity: the brain encased by the skullVertebral or spinal cavity: forms a bony enclosure around the delicate spinal cord.

Ventral Body CavityThoracic cavity: superior; surrounded by the ribs and muscles of the chest

Pleural cavities: each housing a lung, and the medial mediastinum

Pericardial cavity: located within the mediastinum and encloses the heart

Abdominopelvic cavity: inferior to the thoracic cavity and separated by the diaphragm

Abdominal cavity: contains the stomach, intestines, spleen, liver, and other organs

Pelvic cavity: contains the bladder, some reproductive organs and the rectum

The walls of ventral body cavity and the outer surfaces of the organs it contains are covered with an exceedingly thin, double-layered membrane, the serosa, or serous membrane.

Parietal serosa: lines the cavity walls

Visceral serosa: covers the organs in the cavity

Serous fluid: separates the serous layers; thin lubricating fluid; secreted by both membranes

The specific naming of the serous membranes depends on the cavity and organs with which they are associated.

Parietal and visceral pericardia: pericardial cavity and heart

Parietal and visceral pleurae: covers the thorax walls and lungs

Parietal and visceral peritoneum: covers the abdominopelvic cavity and its organs

There are a number of smaller body cavities, many of which are located in the head and most of which are open to the body’s exterior.

Abdominopelvic Regions and Quadrants

Since the abdominopelvic cavity is fairly large and contains many organs, it is helpful to divide it into smaller areas of study. The division method, used primarily by anatomist, uses two transverse and two parasagittal planes to divide the cavity into nine regions

Abdominopelvic Regions and Quadrants Medical personnel usually

prefer to use a simpler scheme to localize and describe the condition of the abdominopelvic cavity organs. One transverse and one median sagittal plane pass through the umbilicus at right angles.

Body Planes and SectionsSagittal Plane: runs

logitudinally and divides the body or organ into right and left portionsMidsagittal or median sagittal plane: when the sagittal plane is directly midline and the parts are symmetrical and equalParasagittal Plane: refers to all other sagittal planes

Frontal Plane: runs longitudinally dividing the body or organ into anterior and posterior portions

Coronal Plane: just another term for the frontal plane

Transverse or horizontal plane: runs horizontally across the long axis of the body or organ dividing it into superior and inferior partsCross sections: tissue sections when organs are sectioned along the transverse plane for microscopic examinationOblique plane: cuts made along a plane intermediate between a horizontal and longitudinal plane

Anatomical Directions1. Anterior: toward the front of the body2. Posterior: toward the back of the body3. Distal: farther from the origin of the body part or

point of attachement of of a limbto the body trunk4. Proximal: closer to origin or attachement5. Inferior: toward the lower part of a structure or

body; below6. Superior: toward the head end or upper part of a

structure or the body; above7. Lateral: away from the midline; on the outer side of8. Medial: toward the midline; on the inner side of9. Superficial: toward or at the body surface10. Deep: away from the body surface; more internal

Body Type and DiseaseThe term somatotype is used to describe a

particular category of body build or physique. Every individual can be classified as belonging to one of three somatotypes:

Endomorph: heavy, rounded physique characterized by large accumulations of fat in the trunk and thighs

Mesomorph: muscular physique

Ectomorph: thin, fragile physique characterized by little body fat accumulation

Knowledge of physique can provide vital information useful in areas such as disease screening and for predicting performance capabilities.

Homeostasis Homeostasis indicates a dynamic state of

equilibrium, or balance, in which internal conditions change and vary, but always within relatively narrow ranges.

Every organ system has a role to play in maintaining constancy of the internal environment.

Characteristics of Control Mechanisms Communication within the body is essential for

homeostasis and is accomplished chiefly by the nervous and endocrine systems. All homeostatic control mechanisms have a minimum of four interdependent components:

1. Receptor or sensor mechanism: some type of sensor that monitors the environment and responds to changes called stimuli, by sending information to the control center

2. Integrating or control center: determines the set point at which a variable is to be maintained, analyzes the input it receives, and then determines the appropriate response

Characteristics of Control Mechanisms3. Effector mechanism: provides the means by

which the control center can cause a response (output) to the stimulus

4. Feedback: the results of the response can then be fed back to influence the stimulus, either depressing it so that the whole control mechanism is shut off or enhanced so that the reaction is continued at an even more vigorous rate

Negative Feedback MechanismsMost homeostatic control mechanisms are

negative feedback mechanisms. An increase in the output of the system feeds back and decreases the input into the system. The net effect is to decrease the original stimulus or reduce its effect, slowing the activity or shutting it off entirely.

Ex. Blood glucose levels (set point range is 80 to 100mg of glucose per milliliter of blood)

If body cells are to carry out normal metabolism, they must have continuous access to glucose. A jelly donut is eaten and broken down into sugar and floods the bloodstream -- blood sugar levels rise, disrupting homeostasis – insulin producing cells in the pancreas are stimulated and respond by secreting insulin into the bloodstream – insulin accelerates the uptake of glucose by body cells and encourages the storage of excess glucose as glycogen in the liver and muscles – blood sugar levels ebb back to normal.

Glucagon, the other pancreatic hormone, has the opposite effect. Skip lunch – glucagon targets the liver causing it to release its glucose reserves into the blood – blood sugar levels increase.

Other feedback systems include:

Body temperature

Heart rate

Blood pressure

Breathing

Blood levels of oxygen and carbon dioxide

Minerals

Positive Feedback Mechanisms In a positive feedback mechanism the result or

response of the mechanism enhances the original stimulus, so that the activity is accelerated or proceeds in the same direction as the initial disturbance.

Ex. Labor ContractionsThe hormone oxytocin enhances labor contractions – increase pressure on the cervix excites pressure receptors located there– rapid impulses are sent to the brain which triggers the release of oxytocin into the blood stream and is then transported to the uterus – the muscles in the uterine wall are stimulated to contract even more virorously, forcing the baby further into the birth canal – when the baby is born the stimulus for oxytocin release ends, shutting off the mechanism

Feed-Forward MechanismsA feed-forward mechanism causes the

feedback loop to anticipate a stimulus before is actually happens.

Ex. Digestive tract stretch

When you eat a meal, the stomach stretches triggering the release of gastric juices – at the same time the stretch stimulus is triggering the small intestines and related organs to increase secretions there as well – before the food has arrived.

Homeostatic Imbalance

Most disease is regarded as a result of homeostatic disturbance, a condition called homeostatic imbalance. Pathophysiology is the study of the underlying physiological processes associated with disease.

Basic Mechanisms of Disease Genetic mechanisms

Pathogenic organisms prions viruses bacteria fungi protozoa pathogenic animals

Tumors and cancer Physical and chemical agents Malnutrition Autoimmunity Inflammation Degeneration