Human Physiology Exam 2

Pulmonary ventilation 

Movement of air into and out of lungs (breathing).

-         No exchange

-          Driven by pressure changes created by diaphragm and thoracic cavity movement

Breathing

mechanical airflow in and out of lungs

External respiration

Gas exchange between alveoli and pulmonary capillaries. (lungs and blood)

§  This occurs across the respiratory membrane.

1.     O₂ diffuses from alveoli→  plasma → blood and binds to hemoglobin

CO₂ diffuses from blood → alveoli

Internal respiration

Gas exchange between systemic capillaries and tissues. (blood and tissues)

-         O₂ diffuses from blood → plasma → tissues

-         CO₂ diffuses from tissues → blood

Cellular respiration

Mitochondrial process where cells use O₂ to produce ATP and generate CO₂.

Pleural cavity

Thin fluid-filled space that provides cushioning and prevents friction

Atmospheric pressure

Pressure exerted by air in the environment (~760 mmHg at sea level).

Intra-alveolar/pulmonary pressure

Pressure inside the alveoli; changes during breathing to move air.

Intrapleural pressure

Pressure inside pleural cavity; normally negative relative to alveolar pressure

Inspiration

Process of drawing air into lungs; occurs when intrapulmonary pressure falls below atmospheric pressure.

Expiration

Process of expelling air; occurs when intrapulmonary pressure rises above atmospheric pressure

Bronchodilation

Widening of bronchi/bronchioles due to smooth muscle relaxation.

Bronchoconstriction

Narrowing of airways due to smooth muscle contraction

Compliance

Ability of lungs to stretch and expand (ΔV/ΔP).

·        High compliance → lungs expand easily

·        Low compliance → lungs are stiff and harder to inflate

Tidal volume

Amount of air inhaled or exhaled during quiet breathing (~500 mL).

Residual capacity (volume)

Air remaining in lungs after maximal expiration. -         Prevents lung collapse and keeps alveoli open.

Vital capacity

Maximum air exhaled after maximal inspiration (TV + IRV + ERV). -         Represents the largest usable volume of air.

Total lung capacity

Total air in lungs after maximal inspiration (VC + RV).

Inspiratory reserve volume

Extra air that can be inhaled after normal inspiration.

Inspiratory capacity

Max air inhaled after normal expiration (TV + IRV).

Expiratory reserve volume

Extra air exhaled after normal expiration.

Functional residual capacity

Air remaining in lungs after normal expiration (ERV + RV).

• This is the lung’s “resting volume.”
  It prevents large fluctuations in blood gases between breaths

Anatomic dead space

Air in conducting zone that does not participate in gas exchange (~150 mL).

• nose to Terminal Bronchiole

Alveolar ventilation

Amount of fresh air reaching alveoli per minute.

= (Tidal Volume − Dead Space) × Respiratory Rate

• This is what actually matters for gas exchange — not just total ventilation

Partial pressure

The force exerted by an individual gas upon a surface and other gases

• Pressure exerted by an individual gas in a mixture of gases.

Oxyhemoglobin

Hemoglobin is bound to oxygen.

Hemoglobin can bind to 4 pieces of oxygen at a time

Deoxyhemoglobin

Hemoglobin is not bound to oxygen.

Carbaminohemoglobin

Hemoglobin bound to carbon dioxide.

Carbonic anhydrase

Enzyme in RBCs that converts CO₂ + H₂O ↔ H₂CO₃ ↔ H⁺ + HCO₃⁻.

BPG (2,3-biphosphoglycerate)

RBC molecule that decreases hemoglobin’s affinity for oxygen (right-shifts curve).

Bicarbonate (HCO3-)

Primary form of CO₂ transport in blood and major blood buffer.

Surfactant

Substance produced by Type II pneumocytes that reduces alveolar surface tension (water molecules sticking together because of hydrogen bonds) and increases compliance

• Prevents collapse

• Hydrophobic substance

Respiratory membrane

Thin barrier between alveolar air and blood (Type I pneumocyte + basement membrane + capillary endothelium).

1.     list the functions of the respiratory system.

o   Regulation of blood pH: CO2 control

o   Gas exchange: O2 in and CO2 out

o   Production of chemical mediators: ACE enzymes in lungs

o   Voice production: movement of air past the vocal cords to make sound and speech

o   Olfaction: When airborne molecules are drawn into the nasal cavity.

o   Protection: Prevents entry of microorganisms and removes them from respiratory surfaces.

transport of gases

o   Movement of O₂ and CO₂ in blood.

1.     This step moves gases between lungs and tissues.

Ciliated pseudostratified columnar epithelium

moves mucus upward

Goblet cells

produce mucus

Basal cells

·        stem cells for maintaining respiratory system

Club (Clara) cells

·        detoxification, regeneration, protection

Smooth muscle lungs

controls airway diameter

Cartilage (trachea/bronchi)

prevents collapse

Type I pneumocytes

·        Simple squamous

·        Very thin

·        95% of surface area

Function: gas exchange

Type II pneumocytes

·        Cuboidal

·        Produce surfactant

Can divide and replace Type I cells

Alveolar macrophages

·        Phagocytose debris and pathogens

Capillary endothelial cells

·        Form diffusion membrane with Type I cells

🔹 1. Nasal Cavity

Epithelium:

·        Pseudostratified ciliated columnar epithelium

·        Goblet cells

Cell Types & Functions:

·        Ciliated cells → move mucus toward pharynx

·        Goblet cells → secrete mucus to trap particles

·        Basal cells → stem cells

·        Olfactory receptor neurons (in superior region) → smell detection

🧠 Function theme: Filter, warm, humidify air

🔹 2. Pharynx

·        Pseudostratified ciliated columnar epithelium (nasopharynx)

·        Stratified squamous epithelium (oro- and laryngopharynx — more abrasion-resistant)

Function:
Protection from swallowed food + air conduction

🔹 3. Larynx

Epithelium:

·        Mostly pseudostratified ciliated columnar

·        True vocal cords = stratified squamous (friction protection)

Cells:

·        Ciliated cells

·        Goblet cells

·        Basal cells

Function:
Air passage + sound production + protection

Trachea

Structure:

·        C-shaped cartilage rings

·        Smooth muscle (trachealis muscle)

Epithelium:

·        Pseudostratified ciliated columnar

Cells:

·        Ciliated cells → move mucus upward

·        Goblet cells → mucus secretion

·        Basal cells → regeneration

 

Function:
Keep airway open + mucociliary escalator.

Primary Bronchi

·first branch to each lung       

Cartilage plates instead of rings

·        More smooth muscle

Epithelium:

·        Pseudostratified ciliated columnar

Function:
Air distribution + adjustable airway diameter.

Bronchioles

Epithelium:

·        Simple ciliated columnar → simple cuboidal (as they get smaller)

Cells:

·        Fewer goblet cells

·        Club (Clara) cells → detoxify substances + secrete surfactant components

·        Smooth muscle (major regulator of airway resistance)

No cartilage here.

Function:
Control airflow resistance (asthma happens here)

Respiratory Bronchioles

·        Simple cuboidal epithelium

·        Some cilia

• first place where gas exchange happens  (external respiration)

Function:
Start of gas exchange.

Alveoli (Respiratory Zone)

This is where structure becomes extremely thin.

Cell Types:

Type I Pneumocytes

·        Simple squamous

·        Very thin

·        95% of surface area

·        Function: gas exchange

Type II Pneumocytes

·        Cuboidal

·        Produce surfactant

·        Can divide and replace Type I cells

Alveolar Macrophages

·        Phagocytose debris and pathogens

Capillary Endothelial Cells

·        Form diffusion membrane with Type I cells

🧠 Function theme:
Site for gas exchange

1.     list the gases that make up the atmosphere.

Nitrogen (~78%) and 593 mmHg

·  Oxygen (~21%) and 160 mmHg/ 105 mmHg in alveoli

• O2 moves from a high concentration gradient to a low concentration gradient in body

·  Argon (~0.9%) and 7 mmHg

·  Carbon dioxide (~0.04%) and 0.3 mmHg/ 40 mmHg in alveoli

·  Trace gases

1.     explain why the percentages of the gases in the atmosphere doesn’t change but partial pressure does (with respect to changes in altitude).

o   The total percentage of gases present doesn’t change at different altitudes, such as when the air is humid or not. But H2O replaces the amount of individual gases present, causing the partial pressure of each individual gas to decrease and change.

Boyles Law

o   The total pressure of a gas mixture equals the sum of the partial pressures of each gas.

·        👉 Air moves because of pressure gradients created by volume changes.

Daltons Law

o   Each gas exerts its own partial pressure.

o   The total pressure of gas mixture is equal to the sum of the pressures of each gas in it.

Ficks Law

Concentration gradient(Membrane permeability)/ Distance (Molecular Weight)

  Diffusion rate depends on:

§  Surface area (↑ area → ↑ diffusion)

§  Concentration/partial pressure gradient (↑ gradient → ↑ diffusion)

§  Membrane thickness (↑ thickness → ↓ diffusion)

Quiet Inspiration

active- requires muscle contraction

1.      Diaphragm contracts

2.      Thoracic cavity and External intercostals contract (volume increases)

3.      Intrapleural pressure (Pressure of the pleural cavity) decreases

4.      Lungs (intrapulmonary volume) expand from low pressure

5.      Intrapulmonary pressure (pressure inside the lungs) decreases

6.      Air flows into the lungs

Quiet Expiration

passive (Relaxing muscles used during inhalation)

1.      1.      Diaphragm relaxes and moves downward

2.      Thoracic cavity and External intercostals fall (volume decreases)

3.      Intrapleural pressure (Pressure of the pleural cavity) increases

4.      Lungs (intrapulmonary volume) relax from high pressure

5.      Intrapulmonary pressure (Pressure inside the lungs) (alveoli) increases

6.      Air flows out of the lungs

FORCED BREATHING

o   This kicks in during exercise, coughing, singing, panic breathing, etc.

Forced Inspiration

active

§  Sternocleidomastoid → lifts sternum

§  Scalenes → elevate first two ribs

§  Pectoralis minor (when arms fixed)- elevates ribs

§  Result:

o   Even greater thoracic expansion

o   Larger drop in intrapulmonary pressure

o   More air pulled in

Forced Expiration

active

·       Internal intercostals → pull ribs downward

·       Abdominal muscles (rectus abdominis, obliques, transversus abdominis) → compress abdominal organs

·       Mechanism:

o   Abdominal organs push diaphragm upward

o   Thoracic cavity volume decreases sharply

o   Intrapulmonary pressure increases significantly

o   Air is forcefully expelled

Air flow

Air flow (F)= (Palv – Patm)/R

1.     Dropping the pressure inside the lungs creates a pressure gradient from high to low that allows air to enter the lungs

1.      The bigger the pressure difference → the more air moves

explain gas exchange in the lungs

o   In lungs:

1.      PO₂ higher in alveoli → O₂ diffuses into blood

2.      PCO₂ higher in blood → CO₂ diffuses into alveoli

1.     This occurs across the respiratory membrane.

2.     O₂ diffuses from alveoli→  plasma → blood and binds to hemoglobin

3.     bicarbonate is converted back into CO₂ —> CO₂ bounded to hemoglobin diffuses from blood → alveoli

4.  Every carbon that is diffused inside a red blood cell is swapped with a chloride ion to keep the cell's neutrality (Chlorine Shift)

explain gas exchange in the tissues

In tissues:

1.      O₂ diffuses from blood → tissues

2.      CO₂ diffuses from tissues → blood

3.     O₂ diffuses from hemoglobin→  plasma → tissues

4.     CO₂ released from tissues→  plasma  → hemoglobin

5.     The majority of CO2 is synthesized into bicarbonate, swapped with chlorine, and released into the plasma

·       Every bicarbonate that is diffused outside a red blood cell is swapped with a chlorine ion to keep the cell's neutrality (Chlorine Shift)

Henrys Law

o  Solubility of a gas that can dissolve in a liquid

o   Cardon dissolves well into water, but oxygen does not dissolve well

o   Oxygen

o   ~98% bound to hemoglobin

o   ~2% dissolved in plasma

o   Carbon Dioxide

o   ~75% as bicarbonate (HCO₃⁻)

• Blood buffer to maintain pH (swaps between weak acid and weak base)

• Adding carbon dioxide makes blood more acidic

o   ~15% bound to hemoglobin

~10% dissolved in plasma

1.     Explain perfusion ventilation coupling.

o   The lungs constantly adjust blood flow in response to air flow

1.      Well-ventilated alveoli receive more blood

2.      Poorly ventilated alveoli receive less blood

o   Ventilation (V) = air reaching the alveoli

o   Perfusion (Q) = blood reaching the alveoli

Right shift

o   (↓ affinity, easier O₂ unloading): Hemoglobin releases oxygen more easily. The red blood cells have less oxygen inside of them/ cant carry or bind to as much oxygen (BAD)

1.     Lower % saturation for the same PO2

o   These factors stabilize the deoxygenated form of hemoglobin.

o   ↑ CO₂

o   ↓ pH (Bohr effect) (acidosis)

o   ↑ Temperature

o   ↑ BPG

Left shift

o   Hemoglobin holds onto oxygen more tightly.

1.      Higher % saturation for the same PO2

2.      ↓ CO₂

3.      ↑ pH

4.      ↓ Temperature (hypothermia)

5.      ↓ BPG

6.      This allows tissues that are metabolically active to get more oxygen.

Occurs in:

Medullary Oblongata

Main control center

·        Dorsal group controls inspiration (stimulates diaphragm)

·        Ventral group controls respiratory pattern (stimulates intercostals and abdominal muscles)

Pons

Modifies patterns set in the medulla

·        Pneumotaxic – inhibits (reduces) inhalation

·        Apneustic – promotes (speeds up) inhalation

Cerebral Cortex

1.      allows voluntary control of breathing

Central chemoreceptors

1.      Found in the medulla

2.      Stimulates a quicker respiratory rate

3.      Respond to ↑ CO₂ → ↑ H⁺ in CSF à ↓ pH (pH and PCO2)

Peripheral chemoreceptors

Main regulator

1.      Detects chemical changes in the blood

2.      Stimulates the respiratory center and causes a quicker respiratory rate

3.      Found in carotid and aortic bodies

4.      Responds to O2, CO2, and pH

·        Respond to ↓ O₂ (<60 mmHg)

·        Decrease in blood pH from high Hydrogen ions

·        Increase CO2 levels

Hypercapnia

↑ CO₂ in blood
Usually due to hypoventilation

Leads to:

·        Respiratory acidosis

Hypocapnia

↓ CO₂ in blood
Usually due to hyperventilation

Leads to:

·        Respiratory alkalosis

Hypoxia

↓ O₂ delivery to tissues

Examples:

·        Anemia

·        CO poisoning

Hypoventilation

Ventilation too low → CO₂ builds up
Leads to hypercapnia

Hyperventilation

Ventilation too high → CO₂ drops
Leads to hypocapnia

Increased Residual Volume

obstructive diseases
Air trapping (emphysema, asthma)

Decreased Total Lung Capacity

restrictive diseases/ shallow breathing
Fibrosis, ARDS

Increased Compliance

Lungs inflate easily but don’t recoil (floppy)
Emphysema (hard to exhale)

Decreased Compliance

Stiff lungs & harder to inflate
Fibrosis, surfactant deficiency

Increased Intrapleural Pressure

Can collapse lung
Pneumothorax

Suffocation

A life-threatening condition where the body is deprived of oxygen.

-         Airway obstruction

-         Indicates failure of oxygen delivery

Cyanosis

caused by increased deoxyhemoglobin in the blood.

-         occurs when too much hemoglobin is not carrying oxygen.

Kidney

·  Filter blood

·  Remove wastes (urea, creatinine, uric acid)

·  Regulate:

·        Blood volume

·        Synthesizes Vitamin D

·        Concentration of blood solutes- Electrolytes (Na⁺, K⁺, Cl⁻, HPO4^-2)

·        pH (H⁺ secretion, HCO₃⁻ conservation)

·  Produce hormones:

·        Renin

·        Erythropoietin

·        Calcitriol

Ureter  

Transport urine from kidneys → bladder

Urinary bladder 

Stores urine

·  Expels urine during urination

Urethra 

Conducts urine to outside the body

Nephron 

Basic functional & working unit of the kidney

Glomerulus 

filters blood into plasma, nutrients, ions, and water (not blood or proteins)

Bowman’s capsule

collects filtrate

Glomerular filtration  

The process where blood is filtered from the glomerulus into Bowman’s capsule

 

Separates needed plasma, nutrients, ions, and water from blood

 

blood plasma leaks through and becomes filtrate

Tubular reabsorption 

Reabsorbs needed substances from filtrate to return to the bloodstream

 

Occurs in the proximal convoluted tubule to distal convoluted tubule

Tubular secretion

unwanted waste and excess nutrients in filtrate become tubular fluid to make urine

 

Occurs in distal convoluted tubule and collecting duct

Urine excretion 

Removal of urine outside the body using urethra