Science 8: Unit B: Cells and
Systems
Topic 6: Body Systems in Humans
(pp. 146-153)
Outcome: Name and describe each of
the five systems.
I. Digestive System
Principal Organs: Mouth, esophagus,
liver, pancreas, stomach, small and large
intestines.
 Major Role: Digesting food into small
particles which can be changed into
energy by cells’ mitochondria.
 Needs Fulfilled: Energy, growth, and
eliminating wastes

II. Respiratory System
Principal organs: Larynx, trachea,
bronchi, bronchioles, lungs, diaphragm,
alveoli.
 Major role: Taking in oxygen into the
bloodstream, and expelling carbon
dioxide. (gas exchange)
 Needs fulfilled: Energy and eliminating
wastes.

III. Circulatory System
Principal Organs: Heart, arteries,
capillaries, veins.
 Major Role: Transporting nutrients to
cells and waste products away from
cells.
 Needs Fulfilled: Energy, eliminating
wastes. (Vital for all needs really).

IV. Excretory System
Principal Organs: Kidneys, ureters,
urethra, bladder.
 Major Role: Filtering and expelling liquid
wastes out of body.
 Needs Fulfilled: Eliminating wastes.

V. Sensory Awareness System

Principal Organs: Brain- hypothalamus,
sensory nerves, motor nerves, muscles, blood
vessels, skin, hair. (Really a combination of
systems working together, coordinated by the
brain.)
 Major Role: Adjusting body’s different systems
to deal with outside environment.
 Needs Fulfilled: Adapting to environment.
Circulatory System Overview

I. Heart - the PUMP of the system.
 II. Arteries - Blood vessels which take blood AWAY
from heart to rest of body. They are located deep
inside your body so that they are safe from damage.
Their thick, muscular walls keep pushing blood to all
parts of the body.
 III. Capillaries - Tiny blood vessels, which are on cell
thick. Nutrients (glucose, oxygen, protein, etc.) and
wastes (carbon dioxide, urea, etc.) pass back and
forth its walls through the process of DIFFUSION.
Every cell in your body is in close contact with a
capillary.
Circulatory System Overview

IV. Veins - Blood vessels which take blood TO the
heart. Blood in veins is low in nutrients and high in
wastes so veins also travel to kidneys and lungs to
get rid of waste products.
 Unlike arteries, veins do not have the muscular
walls to push blood to the heart. Instead, veins
have valves, which block blood from going
backwards. Veins also move blood as they are
moved by muscles. This is why cashiers and other
people who have to stand still for long periods of
time are at risk for damaged veins, and poor
circulation (varicose veins)
Blood

V. Blood - made up of four parts: plasma, red
blood cells, white blood cells, and platelets. The
job of blood is to carry nutrients to cells while
moving wastes away from cells.
 1. Plasma - The liquid portion of blood. Actually
yellowish in color, plasma is mostly water with the
rest being proteins ~ 55% of blood is plasma
 2. Red Blood Cells - These disk-like cells carry the
oxygen molecules that the cells need and the
carbon dioxide molecules the cells need to get rid
of. ~ 40 % of blood.
Blood Cont’d
3. White Blood Cells (WBC) - Help
defend the body against infectious
diseases and foreign particles. Also part
of the immune system ~ 4% of blood.
 4. Platelets - Responsible for blood
clotting anytime there is a wound. ~ 1%
of blood.

Excretory System Overview
The Excretory System is the system
responsible for filtering out and removing
wastes from the body. This system has
four main parts: kidneys, ureters, a
urethra, and a bladder.
 I. Kidneys - most important part of
system. They filter out wastes from
bloodstream and processes them into
urine.

Excretory System Overview
II. Ureters - Two tubes which move urine
from kidneys to bladder. A small amount
of urine is moved every 10 seconds.
 III. Bladder - Stores urine until limit is
reached and nerve sensors are
triggered. The urge to urinate begins
here.

Excretory System Overview

IV. Urethra - Tube that passes urine from
bladder to exit point.
Sensory Awareness System
Not really a body system on its own, but
a group of responses coordinated by the
brain and carried out by different parts of
the muscular, nervous, digestive, and
excretory systems.
 Your skin is fitted with sensory nerves all
along its inside. There ar edifferents
types of sensory nerves: for pain,
pressure, temperature, etc.

Sensory Awareness System
If the temperature of your skin goes past
certain limits, your brain takes action.
 If the sensory nerves signal that your
skin is too cold, your brain sends signals
to your muscles to start quivering,
causing you to shiver. This rapid
movement of muscles causes you to
warm up your body temperature.

Sensory Awareness System

If the sensory nerves signal that your
skin is too hot, your brain sends signals
to blood vessels near your skin to
expand, releasing more heat to the
outside. It also sends signals to other
systems to save water and to excrete
solutes. This causes you to sweat.
Sensory Awareness System

Sometimes a stimulus needs such an immediate
reaction that the signal doesn’t even go to the
brain. Instead, reflex reactions travel from a
sensory nerve, go to the spinal cord and travel
back down to a muscle nerve which performs the
response. This is all automatic and does involve
the brain at all. An example includes the knee-jerk
reaction or placing your hand on a hot surface.
The heat from the surface was the stimulus and
the reflex reaction was you jerking your hand
away.