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Body Systems Notes – January 12, 2015
Levels of Organization: Cells work together to form tissues. Tissues work together to form organs. Organs work
together to form organ systems.
There are 10 organ systems in the human body and they have to work together to maintain homeostasis…
Homeostasis The process of maintaining a stable internal environment.
CIRCULATORY SYSTEM
-Contains the heart and all the blood vessels.
-Function: delivers nutrients and oxygen to various parts of the body by circulating blood
through veins and arteries.
Veins: blood vessels that carry blood to the heart.
Arteries blood vessels that carry blood away from the heart.
Capillaries: smallest blood vessels; site of gas exchange.
What is in blood?
-Red Blood Cells: carries oxygen and nutrients to the different parts of the body and rids the body of CO2 and
waste; made in bone marrow.
-White Blood Cells: helps fight disease and infection by destroying bacteria and germs that enter the body; made
in lymph nodes.
-Platelets: help blood to clot and prevents excess bleeding.
-Plasma: water portion of the blood (55% of blood).
RESPIRATORY SYSTEM
Function: supplies the blood with oxygen by breathing and rids the body of carbon dioxide by exhaling.
-Nose and mouth wets the air.
-A thin flap of tissue (epiglottis) covers the windpipe when you swallow and prevents
food or drinks from entering your lungs.
-Air then travels through your voice box and down your wind pipe where it splits into 2
bronchial tubes and then smaller tubes called bronchioles.
-These tubes end in bunches of tiny round air sacs called alveoli that are covered in
capillaries.
MUSCULAR SYSTEM
Function: provides the force necessary to move the body.
-Muscles can be voluntary (move under your control) or involuntary (move without you controlling them).
There are 3 types of muscles:
Smooth – found only in digestive tract and blood vessel walls (no striations; involuntary).
Cardiac – only found in heart (striations; involuntary).
Skeletal – attached to bones (striations; voluntary).
The muscular system works with the skeletal system to provide movement.
Tendons: connect muscles to bones.
Ligaments: connect bone to bone.
-Skeletal muscle movements are results of pairs of muscles working together.
• One muscle contracts while the other muscle relaxes.
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Muscles always pull; they never push.
This produces thermal energy, and it uses chemical energy.
Thermal energy produces heat that helps keep body temperature constant.
Chemical energy is from glucose. (When glucose is used up, muscles are tired and need to rest.)
SKELETAL SYSTEM
• Includes bones, cartilage, and teeth.
• Each bone in your body is a living organ made of different tissues.
• Cells in bones take in food and use energy.
4 Major Functions:
• Protection – protects vital organs.
• Storage – stores minerals and fat
• Movement – muscles pull bones to move.
• Blood Cell Formation – make blood cells.
Joint: where 2 or more bones come together; some move (hip) and some don’t (skull).
3 types of joints:
1. Sliding joint – bones glide over each other (Example: hand)
2. Ball and socket joint – like a joystick in a computer game (Example: shoulder)
3. Hinge joint – like a door hinge, flex and extend (Example: knee)
INTEGUMENTARY SYSTEM
-Includes your hair, skin, and nails.
-Skin is the largest organ of your body and is your body’s first line of defense against bacteria, viruses, etc.
Functions:
-Acts as a barrier to protect the body from the outside world.
-Helps retain body fluids.
-Helps dispose of waste.
-Regulates body temperature.
-Protects internal living tissues and organs.
-Stores water and fat.
-Acts as a receptor for touch, pressure, pain, heat and cold (contains nerve cells).
3 Layers of Your Skin:
1) Epidermis (outer layer): The epidermis, the outermost layer of skin, provides a waterproof barrier and creates our
skin tone.
2) Dermis (middle layer): contains tough connective tissue, hair follicles, and sweat glands.
3) Hypodermis (deepest layer): contains fat and connective tissue.
DIGESTIVE SYSTEM
Function: breaks down food physically and chemically so that the body can absorb nutrients and water.
Four stages of digestion:
1) Ingestion: taking in food
2) Digestion: breaking down food into nutrients
3) Absorption: taking in nutrients by cells.
4) Egestion: removing any leftover wastes.
Structures involved in digestion:
1) Mouth: teeth physically break food and saliva chemically breaks it down;
“bolus” (ball of food) forms.
2) Pharynx (throat): contains the epiglottis.
3) Esophogas: tube that moves the bolus by peristalsis (wave of muscular
contractions).
4) Stomach: folds called rugae churn the bolus (physical digestion) and mixes it
with gastric acid (chemical digestion; also kills invading bacteria and viruses);
now called “chyme”
5) Small intestine (duodenum, jejunum, ileum): most absorption of nutrients
occurs here.
6) Large intestine: absorbs water from the leftover waste material; produces vitamin K and some B vitamins with
the help of good bacteria.
7) Rectum: area at the end of the large intestine that compacts and stores leftover waste (“feces”).
8) Anus: feces exits the body.
Liver: processes nutrients absorbed from the small intestine and secretes bile, which helps digest fat.
Gall bladder: stores bile, which is produced in the liver.
Pancreas: produces enzymes and hormones that help break down foods.
ENDOCRINE SYSTEM
Function: contains glands that produce hormones to regulate metabolism, growth and development, tissue function,
reproduction, sleep, mood, and homeostasis.
Glands: organs that specialize in the secretion of hormones (chemicals) needed by an organism.
-Hypothalamus (brain): links CNS to pituitary gland.
-Pituitary (brain): secretes growth hormone; called “the master gland”
-Thyroid (neck): secretes thyroxine which regulates metabolism.
-Parathyroid (neck): secretes parathormone, which regulates metabolism
of calcium and phosphate.
-Adrenal glands (kidneys): secretes adrenaline
-Islets of Langerhans (pancreas): secretes insulin and glucagon
EXCRETORY SYSTEM
Function: removes wastes and excess substances from an organism.
Liver: removes harmful substances from the blood, such as bacteria, certain drugs, and hormones; forms urea which
makes up urine; produces bile, which helps digest fat.
Skin: evaporation of sweat removes heat and cools the body.
Lungs: removes carbon dioxide and some water from the body.
THE URINARY SYTEM (PART OF THE EXCRETORY SYSTEM)
Kidneys filter urea from the blood to make urine.
-Pair of kidneys located in middle back and are protected by lower ribs and fat.
-Without the kidneys, it would not take long before the body’s system to become poisoned with unfiltered toxins.
Ureter: tube that connects each kidney to the urinary bladder.
Urinary bladder: where urine is stored.
Urethra: tube that carries urine from the bladder to the outside of the body.
THE NERVOUS SYSTEM
Function: gathers and interprets information from inside and outside the body; makes the body respond to that
information.
Central Nervous System (CNS)
• Includes brain and spinal cord.
• Gathers information from and sends commands to the PNS
• Center of control and coordination in the body.
Peripheral Nervous System (PNS)
• Includes nerves that reach the outer parts of your body
• Gathers information from environment and sends it to brain
• Takes commands from the brain to moves muscles
• Autonomic Nervous System (ANS) controls the automatic processes (smaller part of PNS)
Important Structures in the Central Nervous System (CNS) and Peripheral Nervous System (PNS)
Brain: main control center of the body (thinking, memory, decision making, processing senses, and controlling muscle
movement; protected by the skull.
Spinal cord: contains bundles of neurons and tissues; connects the brain to the other nerves in the body; 33 vertebrae
(bones) protect it from injury.
Neurons: nerve cells; transfers messages through the body in the form of electrical signals/impulses
REPRODUCTIVE SYSTEM
Male: produces and delivers sperm.
• Gonads = testes (produce sperm and testosterone)
• Secondary sexual characteristics result from increased testosterone hormone levels (deeper voice, chest and
facial hair; larger bones).
Female: produces eggs and shelters unborn baby.
• Gonads = ovaries (produces eggs)
• Secondary sexual characteristics result from increased LH, FSH, estrogen and progesterone hormone levels
(wider pelvis, mammary tissue, menstrual cycles).
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Reproductive System Review
Sex cells are called gametes (sperm or egg).
Gametes are produced by the process of Meiosis, in which there are 2 divisions of the cell.
Gametes are haploid because they contain half the amount of genetic information.
When the sperm and the egg unite, a diploid zygote is created (the first cell of a multicellular organism).
Sexual reproduction results in genetically diverse individuals, because offspring are a combination of their
parents.