In this module, we review the basics of how to orient ourselves in the body, then review some of the major organs in each system.
Anatomical Directions
Introduction
In order to understand where organs are in relation to one another, we need to use “directional terms” that allow for accurate communication
We can’t simply use above and below, or up and down, because the body can be in different positions (and can have slightly different meanings—for example, “below” can also mean “deeper”)
Most directional terms can be best understood when grouped as opposite pairs
Anatomical position
We normally think of the body in “anatomical position,” when describing directions
If the body is in another position, the direction still relates to the standard anatomical position. Thus the head is “superior to the neck” no matter if you are upside down.
Anatomical position.
The standard reference position for anatomy is with the body standing, facing forward, with feet slightly apart, the arms to the side, and palms facing forward.
Directions
Front and Back
Anterior – toward the front
Ventral – in humans, same as anterior (ventral literally means “belly-side”)
Posterior – toward the back
Dorsal – in humans, same as posterior (dorsal literally means “back-side”)
Up and down
Superior – toward the top of the body
Inferior – toward the bottom of the body
Side to side
Lateral – toward the sides of the body; away from the body toward the side
Medial – torward the middle of the body
Left – on the left side of the body (the subject’s left, not your left)
Right – on the right side of the body (the subject’s right, not your right)
Inner and outer
Superficial – toward the outer surface of the body
Deep – away from the outer surface of the body
Central – toward the core of the body
Peripheral – closer to the outer areas of the body
Cortical – toward the cortex (outer region) of an organ
Medullary – toward the core or middle (medulla) of an organ
Proximal – closer to the core (or trunk); used appendages (arms, legs, etc)
Distal – further way from core or trunk of body
 Please see the inside front cover of Anatomy & Physiology textbook for examples of usage. The Quick Guide to the Language of Science & Medicine also includes additional examples.
This video outlines the concept of anatomical body position and directions.
Planes of the body
The human body is often represented in cross section, and is often visualized in cross section for medical diagnostics or research (as in CT and MRI scans)
There are different directions into which cross sections can be cut—these different angles of cut are called planes
Frontal plane – divides the body into anterior and posterior sections
Also called coronal plane
Horizontal plane – divides the body into superior and inferior sections
Also called transverse plane
Sagittal plane – divides the body into left and right portions
Midsagittal plane – a sagittal plane that is along the midline of the body
Also called median plane
planes of the body
Planes of the body (NOTE: This subject is NOT in proper anatomical position. The arms should be at the sides, palms forward. So you should imagine the planes the correct anatomical position.)
Click image for larger version (and credits)
Organs and systems
Organs
Organs are made up of different tissues
Organs are organized into different body systems
Organs may belong to more than one system
Different biologists organize them differently
Example
Nervous system could be subdivided
Central nervous system (brain and spinal cord)
Peripheral nervous system (nerves)
Nervous system could be joined to other systems
Neuroendocrine system (nervous and endocrine systems)
Neuroskeletomuscular system (nervous, skeletal, and muscular systems)
leonardo's "organs of a woman"
human nervous system
Major Systems and Organs
This is a brief survey of the major systems and organs of the body.
Integumentary System
Integument = skin
Only one organ in this system –but it’s the largest organ of the body
Therefore, the skin is an organ AND a system
Hair, nails, sweat gland, etc, are usually considered to be accessory structures of a single organ—but a few biologists consider these to be separate organs
Functions of skin
Protection – mechanical, UV radiation, immune “first line” and “second line,” water conservation
Excretion – sweat glands excrete “waste”
Chemical synthesis – vitamin D
Thermoregulation – can regulate heat loss or conservation
Sensation – various sense of touch, temperature, vibration, pain
Skeletal System
Major organs
Bones,ligaments
Major functions
Support – support of internal organs and shape of the body
Protection – protects the brain, heart & lungs, other body organs
Movement – rigid bones and moveable joints forms a system for locomotion, tool use, and other movements
Mineral & fat storage – calcium & phosphorus is stored in bony tissue, and fat is stored within some long bones
Blood production – stem cells for blood cells is located within bone marrow
Muscular System
Major organs
Skeletal muscles (muscle organs)
Major functions
Movement – muscle organs move the skeleton, thus enabling all kinds of movements
Posture – maintaining stable body positions
Heat production – most of the heat of the body is produced by muscles
Nervous System
Major organs
Brain, spinal cord, nerves, sensory organs
Major functions
Control & regulation of various organs and systems
Coordination of functions among organs and systems
Sensation of changes inside and outside the body
Memory – information storage
Endocrine System
Major organs
Pituitary gland, adrenals, pancreas, thyroid, parathyroids, and other endocrine glands
Nearly every organ has an endocrine function (along with its major functions)
Major functions
Control and regulation of other systems
Complements the function of the nervous system
Digestive System
Major organs
Stomach, small and large intestines, esophagus, liver, mouth, pancreas
Gas exchange – moving oxygen into the body and carbon dioxide out of the body
Acid-base balance – maintaining a stabel pH in the body
Fluid and electrolyte balance – maintaining sufficient body fluid and normal concentration of that fluid
Circulatory System
Circulatory can refer to the heart and vessels (the cardiovascular system) or can be used more broadly to also include lymphatic circulation and immunity
Major organs
Heart, arteries, veins, capillaries
Major functions
Exchange of substances between the internal and external environment and between different tissues and systems
Transport of substances such as nutrients, hormones, oxygen, and wastes, around the body
Lymphatic System
Usually considered to include the immune system, or lumped as “lymphatic & immunity,” or may be considered as separate from but complementary to the immune system
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