1.5 Body Structures and Organ Systems

A medical assistant needs an understanding of:

  • Anatomy - study of body structure

  • Physiology - study of  the function

  • Anatomical positions and planes

  • Medical terminology related to the human body

Homeostasis –

  • achieved when body’s systems and processes maintain stability.

  • Organ systems rely on each other to achieve homeostasis.

  • If disease is present within one system, other systems will be affected.

Organization of the Body

  • Cells - smallest living unit in the body

  • Tissues - cells that are similar and organized form together as tissues

  • Organ - two or more tissue types from to create the organs

  • Organ system - a group of organs that work together to perform complicated tasks

Cell Characteristics

  • Basic unit of life

    • Three main parts 

      • Cell membrane - Outer layer

        • Thin and permeable - allows substances to pass through 

      • Cytoplasm

        • liquid containing the cell's structures

        • Mitochondria – makes energy (ATP) for the cell (powerhouse)

      • Nucleus

        • Contains chromosomes (DNA)

Genetic

  • DNA - chemical name for the molecule that carries genetic instructions in all living things.

    • Long strand containing many genes

  • Gene – a portion of  DNA that determines a body trait 

Heredity -

The transfer of genetic traits from parent to child.

  • 46 chromosomes

    • 22 pairs = 44 Total

      • One pair of sex chromosomes, X and Y.

      • XY Male, XX Female

Common Genetic Disorders  

  • Albinism – Born with little or no pigmentation in the skin, eyes, or hair 

    Cystic fibrosis – A life-threatening disease that mainly affects the lungs and pancreas

    Down syndrome - causes intellectual disabilities and physical abnormalities (Three copies of chromosome 21 instead of two)

    Hemophilia – blood disorder; lack of clotting factor

    Phenylketonuria (PKU) – decreased metabolism of PKU. Leads to intellectual disability, seizures, behavioral problems, and mental disorders. All newborns are tested.

Tissue Types

  • Epithelial tissue

    • Covers the body and most organs

      • Protects against invading pathogens and toxins

    • Secretes enzymes 

    • Absorbs nutrients

Nervous tissue

  • Located in the brain, spinal cord, and peripheral nerves

    • Sends impulses or electrical messages to the nerve endings, muscles, and glands in the body. 

Muscle Tissue 

  • Muscle Tissue - contracts and relaxes

    • Skeletal muscle - Attached to skeleton

      • Striated

      • Voluntary

    • Smooth muscle - Located in walls of hollow organs, walls of blood vessels, and dermis of skin.

      • Involuntary 

    • Cardiac muscle - Located in the wall of the heart.

      • Striated.

      • Involuntary

Connective Tissue 

  • Connective tissue - supports, protects, and gives structure to other tissues and organs in the body. 

    • Stores fat

    • Helps move nutrients and other substances between tissues and organs

    • Helps repair damaged tissue.

    • Most abundant

  • Cartilage – joints muscles

  • Adipose - fat

  • Blood – composed of red blood cells, white blood cells, platelets, and plasma. 

  • Osseous (Bone) Tissue  

Body Organs and Systems

  • Organ - Structure formed by organization of two or more different tissue types. 

  • Organ system – organs joined together to carry out vital functions

Respiratory system consists of:

  • Nose

  • Nasal cavity

  • Pharynx

  • Trachea

  • Larynx

  • Bronchi 

  • Lungs 


Organ Systems

  • Integumentary System – skin and accessory organs

    • Body’s first defense against illness and injury

    • Regulates temperature

    • Excretion - cools (perspiration)

    • Sensation

  • Skeletal System – bones and joints

    • Gives body structure and stability

    • Protects organs from injury

  • Muscular System – muscles and connecting structures

    • Responsible for movement

  • Lymphatic System – lymph nodes, spleen

    • Prevents infections with help from white blood cells

  • Respiratory System – lungs and airways

    • Moves air, breathing

    • Delivers oxygen and eliminates carbon dioxide

  • Digestive System – mouth, esophagus, stomach & intestines

    • Liver and pancreas contribute

    • Provides and delivers nutrients

  • Nervous System – brain, spinal cord, nerves

    • Controls all other body systems

  • Endocrine System – glands that secrete hormones

    • Pancreas, pituitary, adrenal, thyroid glands

      • Exocrine glands- release hormones into ducts

      • Endocrine glands - release hormones into bloodstream 

  • Cardiovascular System – heart and blood vessels

    • Pumps blood, provides necessary nutrients, eliminates waste 

  • Urinary System – kidneys, bladder

    • Filters blood, removes waste 

  • Female and Male Reproductive System – ovaries, uterus, vagina, testes, penis

    • Achieve fertilization, produce offspring


  • Anatomical Terminology
    Describes the location of body parts and various body regions

  • Anatomical position 

  • Body is standing upright 

  • Facing forward

  • Arms at the sides and palms facing forward

Directional Anatomical Terms

  • Superior - above

  • Inferior - below 

  • Proximal – closer to attachment

  • Distal – further from attachment

  • Medial – middle of the body

  • Lateral – side of the body

  • Ventral – toward the front of the body (anterior, coronal or frontal)

  • Dorsal – toward the back of the body  (posterior)


Anatomical Planes

  • Sagittal/Midsagittal

    • Divides body into right and left sides 

      Midline through the center of the body

  • Transverse – 

    • Divides body into a top and bottom (superior and inferior)  

Body Cavities 

  • Five Cavities

    • Cranial

      • Brain

    • Spinal

      • Continuation of cranial,  spine

    • Thoracic

      • Chest

        • Lungs, heart, major vessels

    • Abdominal

      • Abdomen

        • Liver, intestines, colon

    • Pelvic 

      • Bladder


Abdominal Regions 

  • RUQ - Right upper quadrant

    • pain - gallbladder

  • RLQ - Right lower quadrant

    • pain  -  appendix

  • LUQ - Left upper quadrant

    • pain - spleen

  • LLQ - Left lower quadrant

    • pain - constipation 

Homeostasis

  • achieved when body’s systems and processes maintain stability.

    • Organ systems rely on each other to achieve homeostasis.

    • If disease is present within one system, other systems will be affected.


Homeostasis – achieved when body’s systems and processes maintain stability.

  • Organ systems rely on each other to achieve homeostasis.

  • If disease is present within one system, other systems will be affected.


Key Terms

  • System - Multiple organs working together to perform complex functions

  • Organ - Body tissues that work together to perform specific functions

  • Anatomical position - Standing erect, arms at the sides of the body, with eyes and palms facing forward, legs parallel with toes pointing forward.

  • Midline - Divides body into equal parts

  • Homeostasis - A balanced, stable state within the body.

  • Mitochondria – makes energy (ATP) for the cell (powerhouse)