Biology 20 AP: Unit E - Respiratory System

Why do we need to breathe?

1. Need oxygen for cellular respiration (energy for cellular metabolism)

2. Carbon dioxide is a by product of cellular respiration and is not used (waste)

3. Take in oxygen and release carbon dioxide to environment

What are the 2 main requirements?

large surface area: maximal oxygen and carbon dioxide exchange

moist environment: dissolves oxygen and carbon dioxide

Stages in respiration

1. Breathing: inspiration (inhaling) and expiration (exhaling)

2. External respiration: exchange of gases between air and blood (alveoli and capillaries - both have very thin walls)

3. Internal respiration: exchange of gases between blood and body tissues

4. Cellular respiration: energy releasing chemical reactions that take place within the cell

Nostrils

entry point for incoming air

external nasal opening

Nasal passage

warms, moistens, and cleans incoming air

lined with ciliated cells and cells that secrete mucous

Pharynx (throat)

passageway for air into respiratory system & food and water into digestive system

located behind mouth

connects mouth & nasal cavity to the larynx and esophagus

Glottis

allows passage of air to lower respiratory tract

opening from pharynx to the trachea

Larynx

holds the vocal chords (vibrate to make sound)

voice box

made form cartilage

Trachea

passageway for air moving to the bronchi

wind pipe

strengthened by semicircular cartilaginous arches

Lung

principal organ of respiration

deep within the body

protected by bone and muscle of chest cavity

Bronchi

cleans foreign particles out of incoming air

smaller branches off of the trachea

cartilage (“c”) rings to provide support

lined with cilia and mucous-producing cells

Bronchioles

cleans foreign particles out of incoming air

small and fibre tubes that branch off of the bronchi

lined with cilia and mucous-producing cells

end with alveoli

Alveoli

tiny sacs enclosed by a membrane (alveolar wall)

surrounded by a network of capillaries

site of actual gas exchange between blood in capillaries and air in alveoli

blood leaving the lungs has a high oxygen content

Pleural membrane

enables lungs to expand and contract with chest movement

double-layered membrane

outer layer attaches to the inside of the chest wall and inner layer attaches to lung

Diaphragm

contraction contributes to inhalation by increasing volume of thoracic cavity

muscle layer

separates the region of the lungs (thoracic cavity) from the region of the stomach and liver (abdominal cavity in mammals)

controls air pressure

Rib cage

protects the lungs

structure is made of bone and muscle

Rib muscles

intercostal muscles

found between ribs and ventral side of ribs

extend to diaphragm

control air pressure along with diaphragm

Mechanics of inhalation

external rib muscles and diaphragm contract

rib cage up and outward

diaphragm downward

volume in thoracic cavity INCREASES

air pressure in lungs DECREASES

Mechanics of exhalation

diaphragm and rib muscles relax

rib cage down and inward

diaphragm up

volume in thoracic cavity DECREASES

air pressure in lungs INCREASES

External respiration (in-depth)

between alveoli + capillaries

O₂ from air in alveoli enter capillaries

CO₂ diffuses out of blood into alveoli

Internal respiration (in-depth)

between capillaries + body tissues

O₂ diffuses from blood into O₂ poor tissues

CO₂ diffuses from tissues into blood

Diffusion (external respiration)

higher concentration of oxygen in air coming in moves to lower concentration in of oxygen in capillaries

Facilitated diffusion (external respiration)

~30% of oxygen is transferred by channel proteins embedded in alveoli cell membranes

with concentration gradient

Oxygen transport

hemoglobin increases oxygen carrying capacity of blood by about 70x

oxygen diffuses into the blood plasma and forms a weak bond with hemoglobin to make oxyhemoglobin

only 1% of O₂ molecules dissolve directly in the plasma

Carbon dioxide transport

7% of CO₂ is carried in the blood plasma

23% of CO₂ is transported by hemoglobin in the form of carbaminohemoglobin

70% combines with plasma water to form carbonic acid

• carbonic anhydrase: enzyme that helps the dissociation and reformation of carbonic acid

Breathing

need to breath to keep concentration of CO₂ in alveoli low

not breathing = CO₂ concentration increases in alveoli

chemoreceptors in brain detect changes in carbon dioxide and oxygen levels

main regulator in air breathers = CO₂

Pneumothorax

medical term for lungs collapsing

air collects b/w the pleura membrane due to an injury

pressure outside of the lungs causes them to collapse

physicians insert a tube into the chest to withdraw the air that has entered the pleura (allows the lung to reinflate)

Tonsilitis (upper respiratory)

infection of the tonsils (in pharynx)

viral infection

tonsils may be surgically removed

tonsils help prevent bacteria and other foreign particles from entering the body

Laryngitis (upper respiratory)

inflammation of the larynx (vocal chords cannot vibrate normally)

most common cause: viral infection

allergies and overstraining the voice can also lead to this disorder

Bronchitis (lower respiratory)

bronchi become inflamed and filled with mucus (leads to coughing)

Pneumonia (lower respiratory)

alveoli become inflamed and fill with liquids

lobular or bronchial

interferes with gas exchange

body becomes starved for oxygen

Pleurisy (lower respiratory)

swelling and irritation of the pleura

pleura = membranes that surround the lungs

Emphysema (lower respiratory)

obstructive respiratory disorder

walls of alveoli break down and lose their elasticity

reduces surface area for gas exchange

causes oxygen shortages to the tissues

Cystic fibrosis (lower respiratory)

genetic condition that affects the lungs

abnormal gene that disrupts the function of cells lining the passageway of the lungs (over production of mucus)

Asthma (lower respiratory)

chronic obstructive lung disease that affects bronchi and bronchioles

breathing difficult or impossible because of reduced air flow

Carcinoma (lower respiratory)

uncontrolled and invasive growth of abnormal cells in the lungs

leading cause of cancer deaths for Canadian men and women

Carcinogenic

cancer-causing

Metastasis

spread of cancerous cells from original site to new locations where they can grow and invade new tissues

Path air follows

Nostril → nasal passage → pharynx → epiglottis → glottis → larynx → trachea → bronchi → bronchioles → alveoli → back out again

Path oxygen follows (atmosphere → hemoglobin)

Nostrils → nasal passage → pharynx → epiglottis → glottis → trachea → bronchi → bronchioles → alveoli → capillaries → RBCs → hemoglobin → oxyhemoglobin