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Learning Outline

The Human BodyPre-A&P

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 book-icon-lionden-fw


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
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.


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

liontrack  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 book-icon-lionden-fw

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 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

Major functions

  • Breakdown and absorption of nutrients
  • Elimination of waste

Respiratory System

Major organs

  • Lungs, bronchial tree, trachea, larynx, nasal cavity

Major functions

  • 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

Major organs

  • Lymph nodes, lymphatic vessels, spleen, thymus, tonsils

Major functions

  • Immunity – protection against outside agents (microbes, toxins, etc) and against abnormal cells (such as cancer), promotion of healing from injury
  • Fluid balance – prevents fluids from building up in tissues by draining away fluids and returning them to the blood

Urinary System

Major organs

  • Kidneys, ureters, bladder, urethra

Major functions

  • Excretion of waste – removing urea (a leftover of protein catabolism), excess water and salts, other wastes
  • Acid-base balance – maintaining a stabel pH in the body
  • Fluid and electrolyte balance – maintaining sufficient body fluid and normal concentration of that fluid

Reproductive Systems

Major organs

  • Male: Testes, vas deferens, prostate, seminal vesicles, penis
  • Female: Ovaries, fallopian tubes, uterus, vagina, breasts

Major functions

  • Reproduction – formation and development of offspring
  • Continuity of genetic information by passing it from generation to generation
  • Nurturing of offspring until they can take care of themselves

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Last updated: March 27, 2019 at 21:06 pm