Show Menu

Anatomy & Physiology #1: The Human Organism Cheat Sheet by

Reference: Seeley's Essentials of Anatomy and Physiology


The scientific study of the structure and relati­onships between body parts.


The scientific discipline of how the body and its parts come together to function.

Structural and Functional Organi­zation

Chemical Level
Atoms combine to form molecules.
Cell Level
Molecules form organe­lles, such as the nucleus and mitoch­ondria, which make up cells.
Tissue Level
A group of similar cells and the materials surrou­nding them.
Organ Level
Two or more tissue types that together perform one or more common functions.
Organ System Level
A group of organs classified as one unit because of a common functi­on/set of functions.
Organism Level
Any living thing considered as a whole.
Chemical → Cell → Tissue → Organ → Organ System → Organism

Charac­ter­istics of Life

The scientific interr­ela­tio­nships among the parts of an organism and how those parts interact to perform specific functions.
The ability to use energy to perform vital functions.
The ability of an organism to sense changes in the enviro­nment and make the adjust­ments that help maintain its life.
Refers to an increase in size of all or part of the organism.
Changes an organism undergoes through time.
Formation of new cells or new organisms.


The ability of all living systems to maintain stable, internal conditions no matter what changes are occurring outside the body.
Four intera­cting components of most homeos­tatic mechan­isms:
Stimulus → Receptor → Control Center → Effector
Stimulus - Indicates that the value of the variable has deviated from the set point/­normal range.
Receptor - Monitors the value and sends data to the control center.
Control Center - Establ­ishes the set point.
Effector - Acts on the signal from the control center to move the variable back to the set point.

Homeos­tatic Mechanisms

Negative Feedback
Positive Feedback
Serves to reduce an excess response and keep a variable within the normal range.
Serves to intensify a response until endpoint is reached.
The response stops the effector.
The response keeps the reaction going.
Ex. Temper­ature & blood pressure regulation
Ex. Childbirth & blood clotting

Body Positions

Anatomical position
A person standing erect with the face directed forward, the upper limbs hanging to the side, and the palms of the hands facing forward.
Supine position
When a person is lying face upward
Prone position
When a person is lying face downward

Direct­ional Terms

Front of the body
Back of the body
Towards the top
Towards the bottom
Towards the trunk
Further from the trunk
Structures toward the midline
Structures farther away from the midline


Sagittal Plane
Divides the body into left and right sides (verti­cally)
Median Plane/­Mid­-Sa­gittal Plane
Passes through the midline of the body; divides the body into left and right halves
Parasa­gittal Plane
Parallel to the sagittal plane, but off to one side
Fronta­l/C­oronal Plane
Divides the body into front and back (verti­cally)
Transv­ers­e/H­ori­zontal Plane
Divides the body into top and bottom (horiz­ont­ally)

Body Parts and Regions

Axial Parts
Head, neck, and trunk
Append­icular Parts
Arms and legs (upper & lower limbs)

The Abdomen

Abdominal quadrants consist of four subdiv­isions.
Abdominal regions consist of nine subdiv­isions.

Body Cavities

The two main cavities are called the ventral and dorsal cavities.

Ventral Cavity - Consists of the following: the thoracic cavity. abdominal cavity, and the pelvic cavity.

Dorsal Cavity - Contains organs lying more posterior in the body. Can be divided into two portions: (1) the upper portion or the cranial cavity houses the brain (2) the lower portion or vertebral canal houses the spinal cord.

Ventral Cavities

Thoracic cavity
It is surrounded by the rib cage, separated from the abdominal cavity by the diaphragm, and is divided into right and left parts by a median structure called medias­tinum.
Abdominal cavity
Bounded primarily by the abdominal muscles and contains the stomach, intest­ines, liver, spleen, pancreas, and the kidneys.
Pelvic cavity
A small space enclosed by the bones of the pelvis and contains the urinary bladder, part of the large intestine, and the internal reprod­uctive organs.
Medias­tinum - Is a partition containing the heart, thymus, trachea, esophagus, and others. Two lungs are located on each side of the medias­tinum.

The abdominal and pelvic cavities are not physically separated and sometimes are called the abdomi­nop­elvic cavity.

Serous Membranes

Serous membranes - Secrete fluid that fills the space between the parietal and visceral membranes. The serous membranes protect organs from friction.

Serous membranes lining the thoracic cavity:
Heart: Perica­rdial cavity - visceral & parietal perica­rdium - perica­rdial fluid
Lungs: Pleural cavity - visceral & parietal pleura - pleural fluid

Serous membranes lining the abdomi­nop­elvic cavity:
Peritoneal cavity - visceral & parietal peritoneum - peritoneal fluid

Mesent­eries & Retrop­eri­toneal Organs

Mesent­eries - Are parts of the peritoneum that hold the abdominal organs in place and provide a passageway for blood vessels and nerves to organs.

Retrop­eri­toneal organs - Are found behind the parietal peritoneum and consists of the kidneys, adrenal glands, pancreas, parts of the intestines, and the urinary bladder.

11 Major Organ Systems

1. Integu­mentary
2. Skeletal
3. Muscular
4. Lymphatic
5. Respir­atory
6. Digestive
7. Nervous
8. Endocrine
9. Cardio­vas­cular
10. Urinary
11. Reprod­uctive

Major Organs of the Body



No comments yet. Add yours below!

Add a Comment

Your Comment

Please enter your name.

    Please enter your email address

      Please enter your Comment.

          Related Cheat Sheets

          Cell Structure and Function Cheat Sheet
          Anatomy & Physiology Unit 1: Intro to Anatomy Cheat Sheet
          Anatomy & Physiology Unit 2: Histology Cheat Sheet