Respiratory System Lung Volumes

Respiratory System

• Primary lung volumes include Tidal Volume (TV), Inspiratory Reserve Volume (IRV), Expiratory Reserve Volume (ERV), and Residual Volume (RV).
• Tidal Volume (TV) is the normal volume of air displaced during normal breathing when extra effort is not applied.
• Inspiratory Reserve Volume (IRV) is the additional air that can be forcibly inhaled after a normal inhalation.
• Expiratory Reserve Volume (ERV) is the additional air that can be forcibly exhaled after a normal exhalation.
• Residual Volume (RV) is the air remaining in the lungs after a forced exhalation, preventing lung collapse.
• Secondary lung volumes include Inspiratory Capacity, Functional Residual Capacity, Vital Capacity, and Total Lung Capacity.
• Inspiratory Capacity (TV + IRV) is the maximum amount of air that can be inhaled after a normal exhalation.
• Functional Residual Capacity (ERV + RV) is the amount of air remaining in the lungs after a normal exhalation.
• Vital Capacity (TV + IRV + ERV) is the maximum amount of air that can be exhaled after a full inhalation.
• Total Lung Capacity (TV + IRV + ERV + RV) is the total amount of air the lungs can hold.

Mechanics of Breathing

• During inhalation, the diaphragm contracts and moves downward, while the external intercostal muscles contract, pulling the ribs up and out to expand the chest cavity.
• During inhalation, the internal intercostal and abdominal muscles relax.
• During exhalation, the diaphragm relaxes and moves upward, while the external intercostal muscles relax.
• During exhalation, the internal intercostal muscles and abdominal muscles contract only during forced exhalation.
• During forced exhalation, the internal intercostal muscles pull the ribs down and in, and the abdominal muscles push the diaphragm up.

Lung Volume Changes

• During inhalation, the chest volume increases as the diaphragm contracts and moves downward, and the external intercostal muscles contract, lifting the ribs outward and upward.
• During inhalation, lung pressure decreases below atmospheric pressure, causing air to rush in.
• During exhalation, the chest volume decreases as the diaphragm relaxes and moves upward, and the external intercostal muscles relax, allowing the ribs to move downward and inward.
• During exhalation, lung pressure increases above atmospheric pressure, pushing air out.
• During forced exhalation, contraction of the internal intercostal and abdominal muscles decreases the chest volume more forcefully, expelling more air.
• Inhaled air consists of approximately 21% oxygen and 0.03% carbon dioxide.
• Exhaled air consists of approximately 16% oxygen and 5% carbon dioxide.

Cilia and Mucus

• Cilia are small hairs lining the nasal cavity and airways, sweeping debris and dirty mucous up the trachea for disposal.
• Mucus coats the cilia and lung tissue, trapping dust and bacteria and allowing gases to dissolve for diffusion through membranes.

Air Warming Path

• As air travels through the respiratory system, it is warmed, humidified, and filtered before reaching the lungs through the nasal cavity, pharynx, larynx, trachea, bronchi and bronchioles, and alveoli.
• The warming of air prevents lung tissue damage from cold air.

Alveoli

• Alveoli are tiny, balloon-like air sacs in the lungs where gas exchange occurs.
• The alveolar wall is extremely thin, approximately 0.5 micrometers (µm) thick.
• Type I alveolar cells are flat, thin, squamous cells that allow easy diffusion of oxygen and carbon dioxide.
• Type II alveolar cells are small, cuboidal cells that produce surfactant.

Gas Exchange Between Capillaries

• Oxygen diffuses from alveoli into capillaries and then into the blood.
• Carbon dioxide diffuses from capillaries into alveoli to be exhaled.

Surfactant

• Without surfactant, alveoli would collapse due to high surface tension, making breathing extremely difficult.
• Surfactant reduces surface tension in the alveoli, preventing their collapse during exhalation.
• Surfactant ensures alveoli remain open for continuous gas exchange.
• Surfactant makes lung expansion easier, reducing the effort needed to inhale.
• Surfactant helps prevent fluid from entering the alveolar space, maintaining proper lung function.

Digestive System

• The order of organs in the GI tract from mouth to end is mouth, pharynx, esophagus, stomach, small intestine, large intestine, and rectum.
• Peristalsis is the involuntary constriction and relaxation of the muscles of the intestine, creating wave-like movements that push the contents forward.
• Peristalsis is associated with ingestion, propulsion, mechanical or physical digestion, chemical digestion, absorption, and defecation.
• Most absorption takes place in the duodenum, located in the first section of the small intestine.
• The duodenum absorbs nutrients, vitamins, and minerals.
• The large intestine absorbs water and electrolytes, such as sodium and potassium.
• The gut biome is mostly located in the large intestine.
• The gut biome breaks down fiber, produces some vitamins, and protects against bad bacteria.
• The wrinkles in the small intestine increase its surface area for absorption.
• Plicae circulares and villi are wrinkle-like structures in the small intestine that aid in absorption.
• Amylase breaks down starch.
• Pepsin breaks down protein.
• Mechanical digestion physically breaks down food particles into smaller pieces, increasing surface area.
• Chemical digestion occurs in the stomach and gallbladder.
• The stomach produces HCl and the enzyme pepsinogen.
• HCl creates an acidic environment in the stomach that activates pepsinogen, turning it into pepsin, which begins protein digestion.
• The gallbladder stores and concentrates bile produced by the liver.
• The gallbladder releases bile into the small intestine to assist in fat digestion.
• Accessory organs help with the breakdown, digestion, and absorption of food without directly contacting the food.
• Salivary glands produce saliva that contains amylase, which begins the breakdown of carbohydrates in the mouth.
• The liver produces bile, which helps emulsify fats, breaking them into smaller droplets to aid in digestion and absorption in the small intestine.
• The pancreas secretes digestive enzymes like lipase, amylase, and proteases into the small intestine and produces bicarbonate to neutralize stomach acid in the small intestine.

Circulatory System

• The circulatory system transports useful molecules and waste products.
• The circulatory system helps regulate body temperature by moving warm blood around.
• Blood consists of plasma (~55%), and formed elements (~45%).
• Plasma consists of soluble minerals and proteins in water.
• Formed elements include Red Blood Cells, White Blood Cells, cell products, and non soluble proteins
• Red Blood Cells (RBCs) are shaped round with a flattened, concave center to maximize surface area.
• RBCs contain hemoglobin, which carries oxygen, and lack a nucleus.
• White Blood Cells (WBCs) are part of the immune system.
• Platelets help clot blood when injured.
• RBCs, WBCs, and platelets all come from the same type of parent cell.
• Arteries carry blood away from the heart, while veins carry blood towards the heart.
• Capillaries are the location of gas, nutrient, waste, and other material exchange.
• Capillaries have more overall surface area than the larger vessels.
• Arteries are muscular and have defined cross-sections to resist and be elastic in the high-pressure system coming from the heart.
• Veins are floppy and low-pressure with less muscle.
• Veins that lack pressure use valves to help prevent backward flow due to gravity.

Circulatory System Interaction with Other Systems

• The circulatory system absorbs nutrients and water from the digestive system, delivers nutrients to the liver for processing via the hepatic portal vein, and provides essential nutrients for hematopoiesis and building hemoglobin.
• The circulatory system provides nutrients and oxygen for muscle contraction.
• The circulatory system removes lactic acid and distributes heat generated by muscle contraction.
• Muscular pumps aid in venous return, and exercise contributes to cardiovascular health and helps prevent atherosclerosis.
• The circulatory system transports various white blood cells, including those produced by lymphatic tissue, and antibiotics throughout the body to maintain health.
• The circulatory system carries excess tissue fluid not able to be reabsorbed by the vascular capillaries back to the lymphatic system for processing.
• The left side of the heart has to pump blood to the entire body.
• The right side of the heart only pumps blood to the lungs.
• The left ventricle has the thickest walls in the heart, it must pump blood to the entire body (systemic circulation).
• The right side (low pressure) only needs to pump blood the lungs (pulmonary circulation).
• The pericardium is a protective double-layered sac around the heart that reduces friction, prevents overexpansion, and helps anchor the heart in place.
• The right atrium receives deoxygenated blood from the body via the superior & inferior vena cava.
• The right ventricle pumps deoxygenated blood to the lungs through the pulmonary valve into the pulmonary artery.
• The left atrium receives oxygenated blood from the lungs via the pulmonary veins.
• The left ventricle pumps oxygenated blood to the body through the aortic valve into the aorta.
• Blood flows through the tricuspid valve into the right ventricle.
• Blood flows through the bicuspid (mitral) valve into the left ventricle.