The respiratory system exchanges gases through breathing, warming and filtering air in the upper respiratory tract, and gas exchange in the alveoli. The urinary system removes waste from the blood through the kidneys and releases urine. The digestive system breaks down food, absorbs nutrients, and eliminates waste through a series of organs like the mouth, esophagus, stomach, intestines and liver.

1. Lecture 9c:
Maintenance Systems

2. Respiratory System
How gases are exchanged with the outside
world
3 steps of Respiration:
1. Breathing
2. Internal exchange of gases between air
and blood in the lungs
3. Internal exchange of gases between blood
and tissue fluid and therefore cells

3. Respiratory System
As it moves from the nose to the lungs, air is:
1. Warmed
2. Filtered to be free of debris
3. Humidified
It is at body temp and saturated with water
when it reaches the lungs
As it moves out, it is cooled and loses much
of its moisture

4. Upper Respiratory Tract
Nasal cavities, pharynx and larynx
Nasal cavities are basically the nostrils and the
path to the mouth/ throat
Pharynx is the passageway from the mouth to the
larynx
Glottis is the flap that covers the trachea when you
swallow, to prevent choking
Larynx is the voicebox, a series of cartilage bands
that vibrate when air is expelled past them

5. Lower Respiratory Tract
Trachea- cartilage lined tube leading from the
larynx down to the
Bronchi- smaller tubes leading to the left and
right lungs, they continue to branch and get
smaller and smaller until they become
Bronchioles- the smallest passages, each end
in a space surrounded by
Alveioli- where the gas exchange occurs

6. Breathing
During inspiration, the diaphragm and
muscles around the ribs cause the volume of
the thoracic cavity to increase, drawing air in
During expiration, the diaphragm and rib
muscles relax, and the lungs recoil, pushing
air out
When hydrogen and CO2 concentrations in
the blood rise, the breathing rate is increased

7. Exchange of gases in the
lungs
Surface area of a humans lungs= 50 times
greater than surface area of skin
Each alveolus is surrounded by a capillary
network
CO2 is at higher concentration in the blood,
O2 is at higher concentration in the air
Simple diffusion causes CO2 to move out of
the blood into the air, and O2 to move out of
the air into the blood

8. Internal gas exchange
Hemoglobin is the molecule in RBCs that carries O2- each
RBC can carry about 1 billion O2 molecules inside it
The O2 is released into the tissue fluid and thus the cells
because
O2 concentration is lower than inside the RBC
Warmer temps
lower pH
All these caused by cellular respiration
So there is a cycle and balance of chemicals between the
blood and tissue fluid

9. Urinary System
Kidneys are organs that do the following:
1. Remove nitrogenous waste, either in
the from of urea or uric acid, from the
blood
2. Maintain the water- salt balance of
the blood
3. Maintain the pH balance of the blood

10. Urinary System
Urine produced by the kidneys flows
through the
Ureter, tubes leading to the
Bladder, which stores the urine until it
is ready to be expelled. Then it flows out
the
Urethra to be expelled from the body

11. Kidneys
Everyone has 2 kidneys
Three major parts of a kidney:
1. Renal cortex - the outer region
2. Renal medulla- cone shaped renal
pyramids
3. Renal pelvis- hollow central area where
urine is collected before it goes to the bladder

13. Nephrons
Nephrons are where urine formation happens
1. Filtration - any small molecules in the
blood move into the nephron capsule
2. Reabsorption- nutrients and water
return to the blood from the proximal tubule
3. Secretion- potentially harmful
substances that are not filtered are moved
into the distal tubule

14. Digestive System
The tasks of the digestive system:
1. Ingest food
2. Break food down into particles that
can be absorbed (= cross plasma
membranes)
3. Absorbs nutrients
4. Eliminates indegestibles

15. Digestive System
Tube- within- a- tube plan- the inner
space of the digestive tract is separated
from the rest of the body- in effect, it is
‘outside’ the body
Found in earthworms on up

16. Digestive System
Mouth- breaks food into small pieces
Teeth- have different shapes depending on what is
eaten
Carnivores have pointy teeth
Herbivores have teeth for grinding and crushing
Omnivores have both types
Salivary glands- secrete saliva which starts
chemical digestion, lubricates and contains
enzymes

17. Digestive System
When it leaves the mouth, a food bolus
goes into the esophagus
The esophagus moves the food down to
the stomach by rhythmic smooth muscle
contractions called peristalsis

18. Digestive System
The Stomach receives food from the esophagus,
stores food, starts the digestion of proteins, and
then moves food on into the small intestine
Produces HCl to make the pH= 2, helps to
break down proteins and also kill bacteria
and other pathogens
Surrounded by muscles which mix the food
and digestive juices

19. Digestive System
Small Intestine- finishes breakdown of carbohydrates,
proteins, fats, nucleic acids and absorbs the nutrients
into the body
The liver produces bile which is sent into the sm.
intestine - breaks up fats
Pancreas produces pancreatic juice, which contains
enzymes that help digestion of all sorts of
chemicals
Liver and pancreas are connected to the small
intestine by ducts

20. Digestive System
The wall of the small intestine is covered
by folds upon folds- villi
Each villi is covered in cells that have
microvilli
These folds increase surface area- which
is needed for the contact of food and the
cells so nutrients can move into the
body

21. Digestive System
Large Intestine- continues absorption of
water, salts and some nutrients, stores
indigestible material until it is eliminated
Contains LOTS of bacteria - help to break
down nutrients but also produce Vitamin
K, necessary for clotting
Feces- the final waste product, is
eliminated from the anus

22. Accessory organs- Pancreas
Pancreas secretes digestive juice into the
small intestine
Also produces and secretes insulin into
the blood

23. Accessory Organs- Liver
Liver has many functions:
Removes toxins from the blood
Produces plasma proteins
Destroys old RBCs
Produces bile
Stores glucose as glycogen- then breaks glycogen
down to return glucose to blood as needed to ensure
constant level
Produces urea