MCAT Biology - The Respiratory System

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thoracic cavity

chamber of the body of vertebrates that is protected by the thoracic wall; contains lungs

Lungs

the primary organs of the respiratory system; location of gas exchange

nares

nostrils; external orifice of the nose

vibrissae

nasal hairs

pharynx

resides behind the nasal cavity and at the back of the mouth; common pathway for both air destined for the lungs and food destined for the esophagus

larynx

lies below the pharynx and is only a pathway for air

glottis

the opening of the larynx, covered by the epiglottis

epiglottis

covers the glottis

vocal cords

two; maneuvered using skeletal muscle and cartilage

trachea

air passes her after larynx; epithelial cells to catch material that has made it past the mucous membranes in the nose and mouth

bronchi

two; pathway into lungs after trachea; epithelial cells to catch material that has made it past the mucous membranes in the nose and mouth

bronchioles

the bronchi continue to divide into smaller structures

alveoli

tiny balloon-like structures in which gas exchange occurs at the end of bronchioles; network of capillaries surrounds to carry oxygen and carbon dioxide; an exceptionally large surface area for gas exchange, approximately 100 m2 in total

surfactant

a detergent that lowers surface tension and prevents the alveolus from collapsing on itself, coats alveoli

pleurae

membranes that surround the lungs

visceral pleura

surface adjacent to the lung

parietal pleura

outer part

diaphragm

a thin, muscular structure that divides the thoracic (chest) cavity from the abdominal cavity; under somatic control, even though breathing itself is under autonomic control

intrapleural space

space within the sac; contains a thin layer of fluid to lubricate the two pleural surfaces

Inhalation

active process; diaphragm flattens and the chest wall expands outward; volume increases and pressure decreases

external intercostal muscles

one of the layers of muscles between the ribs; expand the thoracic cavity

intrathoracic volume

the volume of the chest cavity

negative-pressure breathing

the driving force is the lower (relatively negative) pressure in the intrapleural space compared with the lungs

Exhalation

passive process; Simple relaxation of the external intercostal muscles will reverse the processes of inhalation; decrease in volume and increase in pressure; speed up using internal intercostal muscles and abdominals

internal intercostal muscles

oppose the external intercostals and pull the rib cage down to speed up exhalation

Emphysema

disease characterized by the destruction of the alveolar walls → reduced elastic recoil of the lungs → exhalation becomes extremely difficult

mostly caused by cigarette smoking

spirometer

assess lung capacities and volumes (except residual volume)

residual volume (RV)

the amount of air remaining in the lung after complete exhalation

Total lung capacity (TLC)

maximum volume of air in the lungs when one inhales completely; usually around 6 to 7 liters

Vital capacity (VC)

difference between the minimum and maximum volume of air in the lungs (TLC – RV)

Tidal volume (TV)

volume of air inhaled or exhaled in a normal breath

Expiratory reserve volume (ERV)

volume of additional air that can be forcibly exhaled after a normal exhalation

Inspiratory reserve volume (IRV)

volume of additional air that can be forcibly inhaled after a normal inhalation

ventilation center

collection of neurons in the medulla oblongata; fire rhythmically to cause regular contraction of respiratory muscles

chemoreceptors

specialized sensory receptor which transduces a chemical substance to generate a biological signal

ex. CO2 concentration in blood - ventilation center

hypercarbia/hypercapnia

partial pressure of carbon dioxide in the blood rises; increases respiratory rate

respiratory rate

the rate at which breathing occurs; set and controlled by the respiratory center of the brain; usually measured in breaths per minute

hypoxemia/hypoxia

low oxygen concentration in the blood

hypoventilation

lead to increased carbon dioxide levels and an override by the medulla oblongata which would jump-start breathing

hyperventilation

blow off too much carbon dioxide and ultimately inhibit ventilation

blowing into paper bag

pulmonary arteries

originate from the right ventricle of the heart, how deoxygenated blood gets to the lungs

pulmonary veins

how oxygenated blood leaves the lungs; returns to the left atrium of the heart

thermoregulation

regulation of body temperature

vasodilation

As capillaries expand, more blood can pass through these vessels, and a larger amount of thermal energy can be dissipated

vasoconstriction

As capillaries contract, less blood can pass through them, conserving thermal energy

panting

transfer heat to the environment through evaporation of water in mucous secretions

ex. dogs

lysozyme

nasal cavity, tears and saliva; attack the peptidoglycan walls of gram-positive bacteria

mucociliary escalator

internal airways are lined with mucus, which traps particulate matter and larger invaders. Underlying cilia then propel the mucus up the respiratory tract to the oral cavity, where it can be expelled or swallowed

Macrophages

engulf and digest pathogens and signal to the rest of the immune system that there is an invader

mast cells

preformed antibodies on their surfaces; releases inflammatory chemicals into the surrounding area

the bicarbonate buffer system

body attempts to maintain a pH between 7.35 and 7.45

acidemia

blood pH is lower, and hydrogen ion concentration is higher; increase the respiratory rate

alkalemia

blood pH is higher, and hydrogen ion concentration is lower; decrease the respiratory rate