BIO 004 · Human Anatomy
The Respiratory System
Block 4 · Module 1: The Respiratory System
A reference for the respiratory system video and lab. This page covers the upper and lower respiratory tracts, the larynx, the bronchial tree, the lungs and pleurae, the alveoli, and common respiratory disorders. The focus is on structure.
How to use this sheet Toggle the toolbar above. Notes prints the full reference for review. Study prints as a fill-in-the-blank worksheet. Print it, then write each definition while you watch the video or read your book. Quiz me is on-screen typing practice: type the term, click Reveal to check yourself. The comparison grids respond to Study and Quiz too, with a Reveal button on each row.
The Foundations video gives you a complete foundational understanding of this topic, enough on its own for a foundational course. Learn it first, then move on to the Deep dive, which adds the majors-level material: the larynx, the bronchial tree, and the alveoli.
- Distinguish the upper and lower respiratory tracts and the conducting and respiratory zones.
- Identify the parts of the larynx and the bronchial tree.
- Describe the lungs, the pleurae, and the structure of an alveolus.
- Name common respiratory disorders.
Your pre-work
Work through these the evening before class. None of it is turned in. It is how you learn the material and build your spaced recall.
This is more than a checklist. Ticking these boxes is the start, not the finish. Committing this material to memory and being able to apply it takes considerable time and repeated effort. You are not done when the boxes are checked. Put in the real hours, and keep coming back for frequent recall and review until the material is genuinely yours.
The respiratory tract
Add a labeled view of the full airway from the nose to the lungs.
The larynx
Add a labeled view of the larynx showing its cartilages and the vocal cords.
The lungs and alveoli
Add a labeled view of the lungs with a magnified cluster of alveoli.
The Respiratory System, an Overview
The respiratory system moves air in and out and brings it close to the blood. Its parts are grouped two ways: upper and lower tract, and conducting and respiratory zone.
- Respiratory systemthe organs that move air and bring it close to the blood for gas exchange
- Upper respiratory tractthe nose, nasal cavity, paranasal sinuses, and pharynx
- Lower respiratory tractthe larynx, trachea, bronchi, and lungs
- Conducting zonethe passages that only carry air, from the nose to the terminal bronchioles
- Respiratory zonethe structures where gas exchange happens: the respiratory bronchioles, alveolar ducts, and alveoli
- A note on scopethis page covers the structure of the system; the exchange of gases is a physiology topic and is not covered here
The Upper Respiratory Tract
The upper tract takes in air and conditions it, warming, moistening, and filtering it before it reaches the lungs.
- Nosethe external nose and the nasal cavity, the main entry point for air
- Nasal cavitythe space behind the nose, divided into right and left halves by the nasal septum
- Nasal conchaethe scroll-shaped projections on the lateral walls that swirl the air and increase contact with the warm, moist lining
- Paranasal sinusesair-filled cavities in the frontal, ethmoid, sphenoid, and maxillary bones that drain into the nasal cavity
- Pharynxthe throat, a muscular passage shared by air and food
- Nasopharynxthe upper part of the pharynx, behind the nasal cavity, an air-only passage
- Oropharynxthe middle part of the pharynx, behind the mouth, shared by air and food
- Laryngopharynxthe lower part of the pharynx, which opens into both the larynx and the esophagus
The Larynx
The larynx, the voice box, connects the pharynx to the trachea. It keeps food out of the airway and houses the vocal cords.
- Larynxthe voice box, the airway between the pharynx and the trachea
- Thyroid cartilagethe large shield-shaped cartilage forming the laryngeal prominence, the Adam's apple
- Cricoid cartilagethe ring-shaped cartilage just below the thyroid cartilage
- Epiglottisthe flexible flap that folds down over the laryngeal opening during swallowing to keep food and drink out of the airway
- Arytenoid cartilagesthe paired cartilages that anchor and move the vocal cords
- Vocal cordsalso called the vocal folds, the paired folds that vibrate as air passes to produce sound
- Glottisthe opening between the vocal cords
The Trachea and Bronchial Tree
Below the larynx the airway becomes a branching tree, growing narrower and more numerous at every division. Follow the path of air in order.
- Tracheathe windpipe, held permanently open by C-shaped rings of cartilage
- Carinathe internal ridge where the trachea forks into the two main bronchi
- Main bronchithe primary bronchi, one entering each lung
- Lobar bronchithe secondary bronchi, one to each lobe of the lung
- Segmental bronchithe tertiary bronchi, one to each bronchopulmonary segment
- Bronchiolesthe smallest conducting airways, with smooth muscle walls and no cartilage
- Terminal bronchiolesthe last airways of the conducting zone, just before gas exchange begins
The Lungs and Pleurae
The two lungs fill most of the thoracic cavity. They are not identical: the left lung gives up room for the heart. Compare them.
| Lung | Lobes | Fissures | Note |
|---|---|---|---|
| Right lung | three: superior, middle, and inferior | a horizontal fissure and an oblique fissure | the larger of the two lungs |
| Left lung | two: superior and inferior | an oblique fissure only | smaller, with a cardiac notch that makes room for the heart |
- Apexthe narrow superior tip of a lung, rising just above the clavicle
- Basethe broad inferior surface of a lung, resting on the diaphragm
- Hilumthe indentation on the medial surface where the bronchus and vessels enter and leave
- Parietal pleurathe serous membrane lining the thoracic wall
- Visceral pleurathe serous membrane covering the outer surface of the lung
- Pleural cavitythe thin, fluid-filled space between the two pleurae that lets the lung glide as it expands
The Respiratory Zone and the Alveoli
Past the terminal bronchioles the airway becomes the respiratory zone, where the walls thin out into air sacs and gas exchange becomes possible.
- Respiratory bronchiolesthe first airways of the respiratory zone, with a few alveoli budding from their walls
- Alveolar ductspassages whose walls are lined entirely with alveoli
- Alveolithe tiny air sacs that are the site of gas exchange; the lungs hold hundreds of millions of them
- Alveolar saca cluster of alveoli that share a common space
- Type I alveolar cellsthe thin, flat cells that form most of the alveolar wall, where gases cross
- Type II alveolar cellsthe cells that secrete surfactant, which lowers surface tension and keeps the alveoli from collapsing
- Respiratory membranethe thin barrier between the alveolar air and the blood, across which gases cross
- Pulmonary capillariesthe dense net of capillaries wrapping each alveolus
Respiratory Disorders
Respiratory disorders mostly block airflow or damage the surface where gases cross. Compare the common ones by the structure each one affects.
| Disorder | Structure affected | What it is |
|---|---|---|
| Asthma | the bronchioles | inflammation and narrowing of the bronchioles, causing wheezing and breathlessness |
| COPD | the airways and alveoli | chronic obstructive pulmonary disease, a long-term blockage of airflow that includes emphysema and chronic bronchitis |
| Emphysema | the alveoli | destruction of the alveolar walls, which reduces the surface available for gas exchange |
| Pneumonia | the alveoli | an infection that inflames the alveoli and fills them with fluid |
| Pneumothorax | the pleural cavity | air in the pleural cavity, which breaks the seal and lets the lung collapse |
| Lung cancer | the lung tissue | a malignant tumor of the lung, strongly linked to smoking |
See also: Blood Vessels, Structure and Types for the pulmonary capillaries, and The Alimentary Canal, the next page in this block, which shares the pharynx.
Study questions
Work on answering these in writing, in your own words. They are the questions to bring to class, and good practice for the reasoning the exams ask for.
- Compare the conducting zone and the respiratory zone by structure and where gas exchange happens.
- Trace a breath of air from the nose to an alveolus, naming each structure in order.
- Explain how the structure of an alveolus suits gas exchange.
- Name the muscles of breathing and explain how they change the size of the thoracic cavity.
Step 2 . Retrieval check
Now explain it back, in your own words.
In 60 words or more, pull together what the video just taught you. Include the key concepts. This is the point where the learning actually sticks. After you submit, your spaced-recall cards for this topic unlock.