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 flows over 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 air sacs air sacs lung air sacs 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 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 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 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 space inside alveolus pore for airflow between alveoli Cutaway View of Alveolus (see next slide) Figure Page 715

Respiratory Membrane Area between an alveolus and a pulmonary capillary Oxygen and carbon dioxide diffuse across easily alveolar epithelium capillary endothelium fused basement membranes of both epithelial tissues Figure 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 CO 2 + H 2 OH 2 CO 3 carbonic acid HCO 3 – 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