Anatomy of the Lower Respiratory System – Review Flashcards

These flashcards cover key anatomical structures, histology, and muscle mechanics of the lower respiratory tract for exam review.

Which anatomical structures make up the lower respiratory tract?

Larynx (part), trachea, bronchi, and lungs.

What are the two functional divisions of the respiratory system?

Conducting division (nostrils through major bronchioles; no gas exchange) and respiratory division (alveoli and other gas-exchange regions).

Where does incoming air stop for gas exchange?

In the alveoli—millions of thin-walled microscopic air sacs.

Which organs belong to the upper respiratory tract?

Nose through larynx (in the head and neck).

Which organs belong to the lower respiratory tract?

Trachea through lungs (in the thorax).

State the approximate length and diameter of the trachea.

About 12 cm (4.5 in) long and 2.5 cm (1 in) in diameter.

What type of cartilage supports the trachea and how many rings are there?

16–20 C-shaped rings of hyaline cartilage.

What is the function of the trachealis muscle?

Contracts or relaxes to adjust airflow and allows room for the esophagus to expand while swallowing.

Describe the epithelium lining the trachea.

Pseudostratified ciliated columnar epithelium with mucus-secreting, ciliated, and stem cells.

What is the mucociliary escalator?

Mechanism in which mucus traps inhaled particles and upward-beating cilia move the mucus to the pharynx for swallowing.

Name the outermost connective-tissue layer of the trachea.

Adventitia.

At which vertebral level does the trachea bifurcate?

At the sternal angle, approximately T4.

What is the carina?

An internal medial ridge at the tracheal bifurcation that directs airflow into the right and left main bronchi.

Define the hilum of the lung.

A slit on the mediastinal surface where the lung receives the main bronchus, blood vessels, lymphatics, and nerves (root of lung).

Differentiate between costal and mediastinal lung surfaces.

Costal surface presses against the rib cage; mediastinal surface faces medially toward the heart.

Why is the right lung shorter than the left?

Because the liver elevates the right hemidiaphragm, shortening the right lung.

How many lobes and fissures does the right lung have?

Three lobes (superior, middle, inferior) separated by horizontal and oblique fissures.

How many lobes and fissures does the left lung have?

Two lobes (superior and inferior) separated by a single oblique fissure.

What is the cardiac impression/notch?

An indentation on the medial aspect/apex of the left lung where the heart projects.

Which main bronchus is wider and more vertical, and what is the clinical importance?

The right main bronchus; aspirated objects lodge there more often.

How many lobar (secondary) bronchi does each lung have?

Right lung: 3 (superior, middle, inferior); Left lung: 2 (superior, inferior).

What supports lobar and segmental bronchi instead of C-shaped rings?

Crescent-shaped cartilage plates.

Define a bronchopulmonary segment.

A functionally independent unit of lung tissue ventilated by a segmental (tertiary) bronchus (10 on the right, 8 on the left).

List two key histologic features shared by all bronchi.

Pseudostratified ciliated columnar epithelium and abundant elastic connective tissue.

What is BALT and where is it found?

Bronchus-associated lymphoid tissue; found in the lamina propria of bronchi to intercept inhaled pathogens.

Which vessels supply oxygenated blood to the bronchial tree?

Bronchial arteries arising from the aorta.

What diameter defines a bronchiole and what structural feature do bronchioles lack?

≤1 mm diameter; they lack cartilage.

What is a pulmonary lobule?

The portion of lung ventilated by one bronchiole.

Describe a terminal bronchiole.

Last part of the conducting division; ≤0.5 mm diameter, ciliated cuboidal epithelium, no mucus glands/goblet cells.

Why do terminal bronchioles still have cilia?

To move mucus that drains into them back toward larger passages via the mucociliary escalator.

Which airway marks the beginning of the respiratory division?

Respiratory bronchiole (because alveoli bud from its walls).

What structures do respiratory bronchioles branch into?

Alveolar ducts, which end in alveolar sacs surrounding an atrium.

Approximate number of alveoli per lung and surface area provided.

About 150 million alveoli per lung, providing ~70 m² surface area.

What percentage of the alveolar surface is covered by type I cells and what is their role?

≈95%; thin squamous cells for rapid gas diffusion.

State three functions of type II (great) alveolar cells.

1) Repair alveolar epithelium, 2) secrete pulmonary surfactant, 3) cover ~5 % of alveolar surface.

What is pulmonary surfactant?

A phospholipid-protein mixture that coats alveoli and prevents collapse during exhalation.

Which alveolar cell type is called a dust cell and what is its function?

Alveolar macrophage; phagocytoses debris to keep alveoli clean.

List the three layers of the respiratory membrane.

1) Squamous alveolar cell, 2) shared basement membrane, 3) capillary endothelial cell.

Why must fluid accumulation in alveoli be prevented?

Because gases diffuse slowly through liquid, hindering adequate blood aeration.

Name two pleural layers and the space between them.

Visceral pleura (covers lung), parietal pleura (lines thoracic wall); pleural cavity between them containing pleural fluid.

Give three functions of pleurae/pleural fluid.

Reduce friction, create pressure gradient for lung inflation, compartmentalize to prevent infection spread.

Which muscle is the prime mover of respiration and its nerve supply?

Diaphragm; supplied by the phrenic nerve (C5).

How does diaphragm contraction affect thoracic volume?

It flattens and enlarges the thoracic cavity, drawing air into the lungs.

Role of internal and external intercostal muscles in breathing.

Synergists to diaphragm; stiffen thoracic cage, prevent inward collapse, and add ~1/3 of inspired air volume.

What is the function of scalene muscles during quiet respiration?

Hold ribs 1 and 2 stationary, assisting diaphragm.

Name four accessory muscles used in forced inspiration.

Erector spinae, sternocleidomastoid, pectoralis major, pectoralis minor (also serratus anterior and scalene).

Explain why normal quiet expiration is passive.

Due to elastic recoil of lungs and thoracic cage when inspiratory muscles relax.

Which muscles are primary for forced expiration?

Rectus abdominis, internal intercostals, and other abdominal/lumbar/pelvic muscles.

Describe the Valsalva manoeuvre and give two uses.

Deep breath, glottis closed, abdominal muscles contract to raise intra-abdominal pressure; used in childbirth, defecation, urination, vomiting.