Respiration

Respiration

• Physiological process by which oxygen

moves into internal environment and

carbon dioxide moves out

• Oxygen is needed for aerobic respiration

• Carbon dioxide is produced by same

• Respiratory System works with the

circulatory system to deliver oxygen and

remove carbon dioxide

Pressure Gradients

• Concentration gradients for gases

• Gases diffuse down their pressure

gradients

• Gases enter and leave the body by

diffusing down pressure gradients

across respiratory membranes

Fick’s Law

• Describes the rate at which a substance (such as oxygen) will diffuse across a membrane (such as a respiratory surface)

• Rate is proportional to the pressure gradient across the membrane and to the surface area of the membrane

Surface-to-Volume Ratio

• As animal size increases, surface-to-volume ratio decreases

• Small, flattened animals can use the body surface as their respiratory surface

• Larger animals have special structures to increase respiratory surface, such as gills or lungs

A. single celled organisms use simple diffusion

B. Simple aquatic organisms use their skin with blood vessels close by

C. Advanced aquatic organisms use evaginated structures with blood vessels near by.

D. Few aquatic organisms i.e. sea cucumbers invaginate their respiratory surfaces

E. Land animals invaginated their respiratory surfaces to prevent them from desiccation. Lungs are associated with blood for gas exchange

F. Insects invaginate with a tracheal system that are tubes branched inside the body without an association with a circulatory system.

Aquatic Animals-

Because Oxygen in water is app. .004% compared with 21% in the air, aquatic animals have a difficult time with gas exchange.

Most aquatic animals evolved respiratory organs that are found on the outside of the body called gills.

Gills are usually folded membranes or layered membranes (increase surface area)associated with a circulatory system.

Blood vessels are very close to the surface of the gills

Meeting the 4 basic needs

1. Gills are folded or layered to increase surface area

2. Evagination in water insures moist membranes

3. Some organisms have developed a circulatory system to insure all cells receive oxygen

4. Most gills have a protective covering- operculum, mantel or pedicellaria

Fish Gills

• Most commonly

internal

• Water is drawn in

through mouth and

passed over gills

water flows in through mouth FISH GILL

water flowsover gills,then out

Figure 40.6 Page 710

The gills are layered like pages of a book. One set of gills is layered on top of one another. The water move through the mouth and then over the gills out the operculum. The water is moving in the opposite direction of the blood. This is the counter current exchange system. It allows for maximum exchange of gases.

Countercurrent Flow

• Blood flow runs in the opposite direction of water flow over the filaments

• This enhances movement of oxygen from water to blood

direction of water flow

respiratory surface

direction of blood flow

oxygen-poor blood from deep in body

oxygenated blood back toward body

Figure 40.6 Page 710

Terrestrial animals must prevent desiccation.

Gases must be exchanged across moist surfaces. Also must be protected as surfaces are very delicate.

Most land animals invaginated their respiratory surfaces into lungs, tracheal systems or book lungs.

Earthworms- skin acts like respiratory organ. Must stay moist or will die.

Spiders and other arachnids have book lungs. Look more like invaginated gills

Insects-Tracheal systems - Tubes of trachea leading from the outside of the body inward The openings are called spiracles. The trachea are extensively branched into tracheoles which takes air directly to individual cells.

Lungs-

sac structures-->very complicated, subdivide membranes to increase surface area

Vertebrate Lungs

• Originated in some fishes as outpouching from gut wall

• Allow gas exchange in oxygen-poor aquatic habitats and on land

salamander

reptile

Figure 40.8 Page 711

Vertebrate Lungs

Amphibians have lungs which are like simple sacs but they also have the ability to respire through their moist skin

Frogs breathe via positive pressure breathing- that is air is forced to the lung

Note- Homeotherms (warm blooded) need more oxygen/body weight than poikilotherms (cold blooded)

Birds have well developed lungs and air sacs that allow for unidirectional flow of air in the lungs and *better efficiency of obtaining oxygen

Avian Respiration

• Lungs are inelastic

and connect to a

series of air sacs

• Air is drawn

continually through

each lung

airsacs

airsacs

lung

airsacs

Figure 40.9 Page 711

Birds breathe via negative- pressure breathing- that is air is drawn in by increasing the volume of the lungs

Human Respiratory System

Pharynx (Throat)

Larynx (Voice Box)

Trachea (Windpipe)Pleural Membrane

Intercostal Muscle

Diaphragm

Epiglottis

Bronchiole

Alveoli

Figure 40.10 Page 712

Glottis- opening to larynx

Epiglottis- flap of skin to prevent foreign particles in the trachea

Larynx- cartilage like tube contains vocal cords

Trachea- air duct leading from larynx to thoracic cavity

Epithelial lining is cilliated. This cillia beats in waves to prevent foreign particles from entering the lungs.

Trachea also has cartilage rings to prevent it from collapsing.

The trachea branches into 2 tubes leading to the lungs called bronchi. These continue to branch until it ends at a sac like structure called an alveolus.

Alveolus- one cell thick and surrounded by a capillary bed.

Thoracic Cavity

Pleura covers the lungs (2 layers).

Parietal pleura covers the inside of the thoracic cavity.

Visceral pleura covers the lungs themselves.

In between is pleural fluid that allow the lungs and cavity to slide past one another

Gas Laws

Gases will diffuse evenly in a given volume going from a higher [ ] to a lower[ ]

Boyle's Law

P1V1=P2V2 at a constant temperature a volume of gas varies inversely with its pressure PV=K

Breathing

• Moves air into and out of lungs

• Occurs in a cyclic pattern called

the respiratory cycle

• One respiratory cycle consists of

inhalation and exhalation

Respiratory Cycle

Involves 3 types of pressure

1. Atmospheric- pressure exerted by the surrounding air 760 mmHg

2. intrapulmonic- pressure of air within bronchial tubes- This fluctuates above and below atmospheric pressure because of the air moving in and out with the changing volume of the lungs

3. intrapleural- pressure between the two layers of pleural- During normal breathing this is subatmospheric because the lungs have a tendency to recoil (called compliance) which increases the V of pleural cavity increase V decrease P

inspiration (air into lungs)

1. diaphragm contracts

2. external intercostal muscles contract

Both contracted

Diaphragm is lowered increasing the V of lungs

Intercostal muscles- raises the ribs, pushes the sternum forward also increases V of lungs

1. The parietal pleura pulls with the enlarged thoracic cavity lowering the pressure

2. Because of the fluid between the two layers visceral pleura and the lung expands with the enlarging thoracic cavity

3. Lung increase V and now P decreases and air will flow into the lungs

Expiration (air out of lungs) (passive)- The muscles relax or recoil decrease V thoracic cavity and lungs

Thereby increase of P and air flows out

Inhalation

• Diaphragm flattens • External intercostal

muscles contract• Volume of thoracic

cavity increases• Lungs expand• Air flows down pressure

gradient into lungs

Figure 40.12 Page 714

Normal (Passive) Exhalation

• Muscles of inhalation relax

• Thoracic cavity recoils

• Lung volume decreases

• Air flows down pressure gradient and out of lungs

Figure 40.12 Page 714

Active Exhalation

• Muscles in the abdomen and the internal intercostal muscles contract

• This decreases thoracic cavity volume more than passive exhalation

• A greater volume of air must flow out to equalize intrapulmonary pressure with atmospheric pressure

Control of Breathing

• Medulla oblongata sets main rhythm; centers in pons fine-tune it

• Magnitude of breathing depends on concentration of oxygen and H+

• Brain detects H+, increases breathing

• Carotid bodies and aortic bodies detect drop in oxygen, increase breathing

intercostal nerves - intercostal muscles

Stimulation of these nerves is both voluntary and involuntary

Respiratory center upper part of the medulla- a drop in pH (blood) stimulates respiratory center which stimulates the respiratory nerves.

A drop in pH in the blood can result from an increase of CO2-carbonic acid

red blood cell

air spaceinsidealveolus

pore for airflowbetween alveoli

Cutaway View of Alveolus

(see next slide)

Figure 40.16 Page 715

Respiratory Membrane

• Area between an alveolus and a pulmonary capillary

• Oxygen and carbon dioxide diffuse across easily

alveolarepithelium

capillaryendothelium

fusedbasementmembranesof bothepithelialtissues

Figure 40.16 Page 715

Oxygen Transport

• Most oxygen is carried bound to hemoglobin in red blood cells

• Hemoglobin has a great affinity for oxygen when it is at high partial pressure (in pulmonary capillaries)

• Lower affinity for oxygen in tissues, where partial pressure is low

Bicarbonate Formation

CO2 + H2O H2CO3

carbonic acid

HCO3–

bicarbonate

+ H+

• Most carbon dioxide is transported as bicarbonate• Some binds to hemoglobin• Small amount dissolves in blood

Bronchitis

• Irritation of the ciliated epithelium that lines the bronchiole walls

• Air pollutants, smoking, or allergies can be the cause

• Excess mucus causes coughing, can harbor bacteria

• Chronic bronchitis scars and constricts airways

Emphysema

• An irreversible breakdown in alveolar walls

• Lungs become inelastic

• May be caused by a genetic defect

• Most often caused by smoking

Humans at High Altitude

• Permanent residents of high areas have – More vascularized lungs– Larger ventricles in heart– More mitochondria in muscle

• Acclimatization– Changes in rate of breathing, heart output– Kidney secretes erythropoietin; red cell

production increases

Carbon Monoxide (CO)

• Colorless, odorless gas

• Competes with oxygen for binding sites

in hemoglobin

• Binding capacity is at least 200 times

greater than oxygen’s

• Exposure impairs oxygen delivery