Human Body Orientation Dr Idara

Objectives  At the end of this slide, each student should be able to:  List and describe the various body positions.  Define the body planes and associated directional terms.  Locate and describe the body cavities and their respective organs.  List and describe the anatomical divisions of the abdominal region.  Identify and locate the various body regions.

Definition  Anatomy is the study of structure and the physical relationships involved between body systems.  It is from the Greek language which literally means “to cut apart”.  Physiology is the study of how a structure (which may be a cell, an organ, or an organ system) functions or works and the ways in which they cooperate to maintain life and health of the individual.  Structure determines what functions can occur; therefore, if the structure changes, the function must also change.

Levels of Structural Organization  There are six levels of structural organization. Atoms (at the chemical level) combine, forming the unit of life, the cell.  Cells are grouped into tissues, which in turn are arranged in specific ways to form organs.  A number of organs form an organ system, which performs a specific function for the body (which no other organ system can do). Together, all of the organ systems form the organism, or living body.

Maintaining Life  To sustain life, an organism must be able to maintain its boundaries, move, respond to stimuli, digest nutrients and excrete wastes, carry on metabolism, reproduce itself, and grow.  Survival needs include food, oxygen, water, appropriate temperature, and normal atmospheric pressure. Extremes of any of these factors can be harmful.

Homeostasis  It is the ability or tendency of an organism or a cell to maintain internal equilibrium by adjusting its physiological processes.  For the body to function normally, it must constantly monitor both its internal and external environment and make the appropriate adjustments. The body needs homeostasis to survive.

Homeostatic control  Homeostasis is maintained by control systems that detect and respond to changes in the internal environment.  It has three basic components:  Receptor( Sensor)  Control Center  Effector

 Stimulus- produces a change to a variable (the factor being regulated).  Receptor- detects the change. The receptor monitors the environment and responds to change (stimuli).  Input- information travels along the (afferent) pathway to the control center. The control center determines the appropriate response and course of action.  Output- information sent from the control center travels down the (efferent) pathway to the effector.  Response- a response from the effector balances out the original stimulus to maintain homeostasis.

Afferent and Efferent Pathways  Afferent pathways- carry nerve impulses into the central nervous system. For instance, if you felt scorching heat on your hand, the message would travel through afferent pathways to your central nervous system.  Efferent pathways- carry nerve impulses away from the central nervous system to effectors (muscles, glands).  The feeling of heat would travel through an afferent pathway to the central nervous system. It would then interact with the effector and travel down the efferent pathway, eventually making the person remove their hand from the scorching heat.

Feedback Mechanisms

Negative Feedback Mechanisms  When the feedback loop opposes the stimulus, it is referred to as a negative feedback.  Most homeostatic control systems are negative feedback systems, which act to reduce or stop the initial stimulus. This in turn changes the variable back to its original state or ideal value.  E.g. when body temperature rises beyond normal levels, some nerve endings ( receptors) become stimulated and this information is sent to the Control Center which is the Hypothalamus which activates Effectors to bring the body temperature to normal.

 Sweat glands in the skin will be activated to stimulate sweating which will lead to cooling of the body.  There is also dilation of blood vessels to expel heat.  When the body is then cool, the information is also sent to the control center which then activates the effectors to stop stimulating the sweat glands.

Positive feedback Mechanisms  Positive feedback increases a change away from the ideal set point( the stimulus becomes increased).  It is often a harmful cycle if it is not broken, but it can also be useful.  A good example of a positive feedback system is child birth. During labor, a hormone called oxytocin is released that intensifies and speeds up contractions. The increase in contractions causes more oxytocin to be released and the cycle goes on until the baby is born. The birth ends the release of oxytocin and ends the positive feedback mechanism.

The language of anatomy  Body positions  The body can assume many positions and therefore have different orientations.  Scientists developed what is called the anatomical position to avoid confusion.

The Anatomical position  In the anatomical position, the body is assumed to be standing erect, face forward, with feet parallel and arms hanging at the side, with palms facing forward.  Other body positions that are important to note are prone, supine e.t.c.

 In the supine position, the patient is lying face upward, on the back  In the prone position, the patient is lying face downwards, on the stomach.

Directional terms  Superior (cranial or cephalic) means toward the head or upper body.  Inferior (caudal) means away from the head or toward the lower part of the body.  Anterior (ventral) refers to body parts toward or on the front of the body.  Posterior (dorsal) refers to body parts toward or on the back of the body.  Medial refers to body parts located near the middle or midline of the body.  Lateral refers to body parts located away from the midline  Note: any body part can be either superior or inferior depending on your reference point.

 Proximal refers to body parts close to the point of reference of the body.  Distal refers to the body parts away from the point of reference.  External means on the outside.  Internal refers to structures on the inside.  Superficial means toward or at the body’s surface.  Deep means away from the body’s surface.  Central refers to locations near the center of the body.  Peripheral refers to the extremities or the surrounding.

Body planes  A plane is an imaginary line drawn through the body or organ to separate it into specific regions.  Transverse or horizontal plane- divide the body into superior and inferior parts.  Median or midsagittal plane- divides the body into right and left halves.  Sagittal plane- run parallel to midsagittal but aren’t always in the midline.  Frontal plane or coronal plane- divides the body into anterior and posterior sections.

Body cavities  The body has 2 cavities that house and protect organs, the dorsal (posterior) cavity and the ventral (anterior) cavity.  The larger anterior cavity is subdivided into the thoracic cavity and abdominopelvic cavity.  These two cavities are separated by the diaphragm.  The thoracic cavity contains the heart, lungs and large blood vessels.  The abdominopelvic cavity contains digestive organs, urinary and reproductive organs.

Posterior Cavity  Also called the cranial cavity.  It houses the brain and spinal cord  It is the smaller of the two cavities.

Body regions  The abdomen can be divided into 4 quadrants and 9 regions.  4 quadrants  -upper left quadrant ULQ  -upper right quadrant URQ  Lower left quadrant LLQ  -lower right quadrant LRQ

 9 regions  Epigastic region- located superior to the umbilical region.  Right and left hypochondriac- located on either side of the epigastric region and contain the lower ribs.  Umbilical- centrally placed, houses the naval or belly button.  Right and left lumbar- lateral to the umbilical region.  Hypogastric region- lies inferior to the umbilical region.  Left and right iliac or inguinal region- lateral to the hypogastric region.

 Any questions?