Plant and Human Gaseous Exchange

Leaf Structure and Function

Leaf Functions

• Photosynthesis: Production of glucose (food).
• Gas Exchange: Facilitates intake and output of gases.
• Transpiration: Water loss through stomata.

Stem Functions

• Transportation: Movement of food to plant parts via phloem.
• Water and Mineral Transport: From roots to leaves via xylem.
• Anchoring: Support through roots and root hairs.
• Storage: In plants like potatoes and carrots.

Leaf Anatomy

• Petiole: Stalk attaching blade to the stem.
• Midrib: Central vein.
• Blade: Broad, flat part.
• Margin: Edge of blade.
• Veins: Network transporting water/salts and supporting leaf.

Internal Structure of a Leaf

• Cuticle: Waxy layer reducing water loss.
• Epidermis: Upper and lower cell layers allowing light penetration.
• Mesophyll:
  • Palisade Mesophyll: Elongated cells with chloroplasts below epidermis.
  • Spongy Mesophyll: Irregular cells with air spaces for gas exchange.
• Veins: Transport via xylem (water) and phloem (nutrients).
• Lower Epidermis: Contains stomata.
• Stomata: Pores for gas exchange, regulated by guard cells.

Gas Exchange in Leaves

• Night:
  • Respiration: Oxygen used in cells, lower concentration in mesophyll.
  • Oxygen Diffusion: From outside to inside.
  • Carbon Dioxide: Higher inside, diffuses out.
• Daylight:
  • Photosynthesis: Uses CO2, produces O2.
  • Oxygen Concentration: Diffuses out due to increase.
  • CO2 Diffusion: Enters for photosynthesis.

Stomata Functionality

• Guard Cells:
  • Turgid: Open stomata for gas exchange.
  • Flaccid: Close stomata to prevent water loss.
• Photosynthesis Equation: CarbonDioxide + Water [Light Energy] -> Glucose + Oxygen.
• Wilting: Flaccid guard cells close stomata to conserve water.

Gaseous Exchange in Humans

Necessity of Gaseous Exchange

• Essential for energy production (growth, reproduction via aerobic respiration).
• Constant O2 supply and CO2 removal required.

Why Not Skin?

• Surface Area to Volume Ratio: Too small for effective diffusion.
• Impermeable Skin: Prevents gas exchange to conserve water.

The Respiratory System

Lungs

• Large, moist surface area for gas exchange.

Pathway of Air

1. Nose/Nasal Cavity: Filters air.
2. Trachea: Connects mouth to lungs.
3. Bronchi: Divides into lungs.
4. Bronchioles: Further subdivision.
5. Alveoli: Site of gas exchange.

Mechanism to Remove Dust

• Goblet Cells: Produce mucus.
• Ciliated Epithelial Cells: Move mucus to throat.

Alveoli

• Surrounded by capillaries, site of gas exchange.

Process of Gaseous Exchange

1. Deoxygenated Blood: To alveoli via pulmonary artery.
2. Oxygen Diffusion: Dissolves in alveoli moisture, enters blood.
3. Oxygenated Blood: To heart via pulmonary vein.
4. Hemoglobin: Transports oxygen.
5. CO2 Diffusion: From blood to alveoli.
6. Exhalation: CO2 removed.

Inhalation and Exhalation

Inhalation

1. Diaphragm Contraction: Pulls down, increases thorax volume.
2. Intercostal Muscles Contract: Rib cage expands.
3. Volume/Pressure Changes: Pulls air into lungs.

Exhalation

1. Diaphragm Relaxation: Returns to dome shape.
2. Intercostal Muscles Relax: Ribs descend.
3. Volume/Pressure Changes: Pushes air out.

Composition of Inhaled and Exhaled Air

• Oxygen: Higher in inhaled air.
• Carbon Dioxide: Higher in exhaled air.
• Nitrogen: Remains unchanged.

Additional Points

• Lung Capacity and Breathing Rate: Varies with activity.

Exercise and Fitness

Pulse Rate and Fitness

• Unfit Person: Higher pulse rate.
• Recovery Time: Fit person recovers quicker.
• Lower Pulse: Reduces disease risk, prolongs life.

Smoking and Its Effects

Nicotine

• Raises blood pressure, heart rate.
• Narrows blood vessels, risk of heart issues.

Carbon Monoxide

• Reduces O2 carrying capacity in blood.
• Impact on fetal growth in pregnant smokers.

Emphysema

• Smoking-induced, damages alveoli, reduces gas exchange surface.

Respiratory Surfaces

Characteristics

• Large Surface Area: Fast gas exchange.
• Thin: Short diffusion path.
• Moist: Facilitates diffusion.
• Good Blood Supply: Maintains gradient.

Gas Exchange

• Oxygen enters blood, CO2 removed via respiratory surfaces.