Human Body Systems
Levels of Organization
Remember, the human body is organized in several levels, from the simplest to the most complex. . .
Cells – the basic unit of life
Tissues – clusters of cells performing a similar function Organs – made of tissues that perform one specific function
Organ Systems – groups of organs that perform a specific purpose in the human body
***The purpose of the organ systems is for the human body to maintain homeostasis.
The Human Body Systems
The human body systems are as follows:
-- nervous system -- integumentary system -- respiratory system -- digestive system
-- excretory system -- skeletal system -- muscular system -- circulatory system -- endocrine system -- reproductive system -- lymphatic (immune) system
The Digestive System
Purpose: to break down food particles into simpler molecules that can be absorbed into the bloodstream and used by the body
Major Organs and their Functions:
Mouth – to chew and grind up food physically
-- saliva begins the chemical breakdown of starches
Esophagus – muscular tube connecting mouth to stomach Stomach – churns breaking down food physically
-- produces enzymes to break down food chemically
Pancreas – produces enzymes which chemically breaks down starches, proteins and fats
Liver – produces bile, which physically breaks down fats into smaller fat droplets
Gallbladder – pouch-like organ that stores bile for future use Small Intestine – completes most chemical digestion
--- absorbs nutrients through vili
Large Intestine – removes water from the undigested food and eliminates waste from the body
The Digestive System
The Excretory System
Purpose: to rid the body of wastes, including excess water and salts
Major Organs and Their Functions
Kidneys – the main organs of the excretory system
-- the kidney filters out urea, excess water and other
waste products from the blood which eventually travel out of the kidney as urine
-- eventually they travel through the ureter to the urinary bladder
Rectum – solid (food) waste travels out of the body through the rectum
Skin – sweat glands remove excess water and salts from the body
Lungs – expel the waste gas carbon dioxide
The Excretory System
The Respiratory System
Purpose: to provide the body with a fresh supply of oxygen for cellular respiration and remove the waste product carbon dioxide
Major Organs and Their Functions
Nose (nasal cavity) – internal entry and exit point for air Trachea – the “windpipe”, or tube that lead into your lungs
-- a piece of skin, called the epiglottis, covers the
trachea when you swallow, preventing food from entering Bronchial Tubes- branching tubes from the trachea in each of the lungs leading to the alveoli ( tiny air sacs) which pick up carbon dioxide waste and distributes fresh air to the blood Diaphragm- muscle below your lungs allowing you to
breathe
Image of the Respiratory System
The Circulatory System
Purpose: to transport oxygen and nutrients to body cells for energy and to pick up wastes to deliver to parts of the
excretory system.
Major Organs and Their Functions
Heart – the major muscle of the circulatory system
-- the main function of the heart is to pump oxygen poor blood to the lungs and oxygen rich blood to the rest of the body.
-- the right side of the heart is fills with oxygen poor blood from the body , the left side of the heart fills with oxygen rich blood from the lungs to be delivered to the rest of the body
Arteries – carry oxygen rich blood away from the heart and to the major organs of the body
Veins – carry oxygen poor blood back to the heart away from the major organs of the body
Capillaries – small blood vessels where gas exchange occurs Blood -- red blood cells contain hemoglobin, an iron-rich
protein that carries oxygen
-- white blood cells function in the immune system -- platelets help in blood clotting
Image of the Circulatory System
The Nervous System
Purpose: to coordinate the body’s response to internal and external stimuli
Major Organs and Their Functions Brain – control center of the body
-- consists of cerebrum (controls thought and senses) and cerebellum (balance and coordination)
--brainstem controls involuntary organs functions
Spinal Cord – sends instructions from the brain to the rest of the body and vice versa
Nerves – conduct impulses to muscle cells throughout the body
The Skeletal System
Purpose: to provide structure and support to the human body; protect vital organs; make new blood and stores important minerals
Major organs
-- bone- give the body shape and support
-- protects the brain, heart, lungs and spinal cord
-- new blood is produced in the marrow of long bones -- stores minerals for use by the body
-- attached to muscle by tendons to move the body --calcium is an important mineral for bone strength
The Muscular System
Purpose: works with the skeletal and nervous system to move the body
-- muscle contractions can be voluntary or involuntary -- voluntary muscles work under your control
-- involuntary muscles you can’t control Major organ is muscle
There are 3 main muscle types:
--smooth muscle- involuntary muscle ex. stomach
-- skeletal muscle- voluntary muscle attached to bones -- cardiac muscle- only found in the heart
The Integumentary System
Purpose: to cover and protect internal organs, to regulate body temperature, give a sense of touch
Major Organs and Their Functions
Skin – the skin is the body’s first line of defense
-- the skin is also part of the excretory system as it releases waste through perspiration (sweating)
--the skin helps the body maintain normal body temperature by sweating when hot and giving you goose bumps when you are cold.
-- the skin has many receptors for touch to allow you to feel textures and sense pain
The Endocrine System
Purpose: to control growth, development, metabolism and reproduction through the production and secretion of
hormones
Major Organs
-- hypothalamus -- pituitary gland -- thyroid
-- parathyroid
-- adrenal glands -- pancreas
-- testes -- ovaries
The Immune System
Purpose: to remove infectious diseases and other pathogens from the human body
Major Organs and Their Functions
Skin – also called the integumentary system, the skin is the body’s first line of defense
White Blood Cells – recognize disease agents (antigens) and create antibodies to tag and remove these antigens
-- phagocytes are the white blood cell type that actually eats and destroys these antigens
Lymph Nodes – help restore fluid lost by the blood and return it to the circulatory system
