Thoracic Cavity Anatomy and Respiratory Mechanics

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Questions and Answers

Which statement accurately describes the role of the larynx in the respiratory system?

  • It contains the vocal cords and prevents food from entering the lower respiratory tract. (correct)
  • It serves as a major part of the bronchial tree.
  • It prevents the entry of air into the digestive tract.
  • It is the primary site for gas exchange.

What is NOT a characteristic associated with pulmonary ventilation?

  • Primarily regulated by the diaphragm.
  • Involves both inhalation and exhalation.
  • Occurs in the alveoli. (correct)
  • Depends on pressure changes within the thoracic cavity.

Which type of cell is responsible for cleaning debris from the alveoli?

  • Type 1 pneumocytes
  • Surfactant-producing cells
  • Macrophages (correct)
  • Goblet cells

What anatomical feature is essential for the structural integrity of the bronchial tree?

<p>Cartilage rings (B)</p> Signup and view all the answers

Which of the following statements about the respiratory membrane is incorrect?

<p>It is a complex structure including muscle layers. (B)</p> Signup and view all the answers

What physiological response is triggered by cooling and wetting the face and nose?

<p>Diving reflex (B)</p> Signup and view all the answers

What is the average duration a person can hold their breath?

<p>30-90 seconds (C)</p> Signup and view all the answers

How does the diaphragm change shape when it contracts?

<p>It flattens (D)</p> Signup and view all the answers

Which muscles are primarily responsible for expiration during forced breathing?

<p>Internal intercostals (A)</p> Signup and view all the answers

What is the current world record for holding one's breath?

<p>24 minutes 37 seconds (D)</p> Signup and view all the answers

What happens to air volume in the thorax when there is an increase in thoracic volume?

<p>Air flows into the thorax (D)</p> Signup and view all the answers

Which joint type is found between the ribs and the sternum, specifically at the first rib?

<p>Cartilaginous joint (C)</p> Signup and view all the answers

What role do accessory muscles play in respiration?

<p>They are active only when needed (C)</p> Signup and view all the answers

What does the contraction of the diaphragm do to the thoracic cavity?

<p>Increases the volume of the thoracic cavity (A)</p> Signup and view all the answers

Which of the following joints allows for articulation between the thoracic vertebrae and ribs?

<p>Costotransverse joint (C)</p> Signup and view all the answers

What is the primary function of thoracic joints?

<p>To allow movement (C)</p> Signup and view all the answers

Which of the following correctly describes the external intercostals?

<p>They lift the rib cage during inspiration. (D)</p> Signup and view all the answers

During expiration, what occurs with the pressure inside the thorax?

<p>Pressure increases (B)</p> Signup and view all the answers

What is the characteristic of a costochondral joint?

<p>It is a cartilaginous joint (A)</p> Signup and view all the answers

What occurs when thoracic volume decreases during respiration?

<p>Air flows out of the thorax (A)</p> Signup and view all the answers

How do the muscles and joints interact during thoracic movement?

<p>Muscles create movement enabled by joints (D)</p> Signup and view all the answers

What primarily causes the thoracic cavity to expand during normal quiet inspiration?

<p>Contraction of the diaphragm and contraction of external intercostals (B)</p> Signup and view all the answers

Which type of muscles primarily contribute to forced expiration?

<p>Internal intercostals and accessory muscles (B)</p> Signup and view all the answers

What is the role of accessory muscles during forced inspiration?

<p>To further increase cavity volume and aid in deeper breaths (D)</p> Signup and view all the answers

What happens to the diaphragm during normal quiet expiration?

<p>It relaxes and reverts to a dome shape (A)</p> Signup and view all the answers

What is the main purpose of the internal intercostals during forced expiration?

<p>To depress the ribs and reduce cavity volume (D)</p> Signup and view all the answers

What is the primary function of the pleural fluid in the thoracic cavity?

<p>To enable frictionless movement between lung surfaces (A)</p> Signup and view all the answers

How does the movement of the thoracic wall affect lung volume during inspiration?

<p>It increases thoracic volume leading to decreased lung pressure (D)</p> Signup and view all the answers

Which of the following describes a pneumothorax?

<p>Collection of air in the pleural space causing lung collapse (C)</p> Signup and view all the answers

What happens to the lungs during expiration?

<p>Lungs recoil to push air out (B)</p> Signup and view all the answers

What role do the visceral and parietal pleura play in respiration?

<p>They enable the lungs to move with the thoracic wall (B)</p> Signup and view all the answers

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Study Notes

Thoracic Cavity Anatomy

  • Thoracic cage: Formed by ribs, sternum, and thoracic vertebrae. Includes sternocostal, costochondral, and interchondral joints; costovertebral, and costotransverse joints.
  • Most thoracic joints are synovial, except the first sternocostal joint and costochondral joints, which are cartilaginous.
  • Thoracic joints' movement is facilitated by respiratory muscles.

Respiratory Mechanics

  • Boyle's Law: Pressure and volume of a gas are inversely related. Increasing thoracic volume decreases pressure, causing air to flow in (inspiration). Decreasing thoracic volume increases pressure, causing air to flow out (expiration).
  • Quiet inspiration: Diaphragm contraction (flattens) and external intercostal contraction (lifts ribs).
  • Forced inspiration: Above actions plus accessory muscle contraction to further expand the thoracic cavity.
  • Quiet expiration: Passive process; diaphragm relaxes (dome shape), external intercostals relax.
  • Forced expiration: Internal intercostal contraction (depresses ribs) and accessory muscle contraction to further decrease cavity volume.

Respiratory Muscles

  • Primary muscles: Diaphragm and intercostal muscles.
  • Diaphragm: Sheet of skeletal muscle separating thorax and abdomen; contraction flattens it, expanding the thoracic cavity and compressing the abdominopelvic cavity.
  • External intercostals: Lift rib cage, expanding the thoracic cavity (inspiration—quiet and forced).
  • Internal intercostals: Depress rib cage, decreasing thoracic cavity volume (forced expiration only).
  • Accessory muscles: Assist in forced inspiration and expiration; specific names not required.

Respiratory Membrane and Cell Types

  • Respiratory membrane: Facilitates gas exchange; composed of capillary endothelium, simple squamous epithelium, Type II pneumocytes, and a fused basement membrane.
  • Macrophages: Remove debris from alveoli.

Lung Expansion and Pleura

  • Pleura: Visceral pleura covers lungs, parietal pleura lines thoracic wall; pleural fluid lubricates and binds lungs to thoracic wall enabling lung expansion.
  • Lung expansion and contraction follow changes in thoracic cavity volume due to the pleural linkage.

Breath-Holding and Diving Reflex

  • Average breath-holding time: 30-90 seconds.
  • Diving reflex: Activated by cooling and wetting face; prioritizes oxygen to heart and brain, extending breath-holding time. Present in infants up to about 6 months.
  • World record breath-holding time: 24 minutes 37 seconds (with pure oxygen inhalation).

Pneumothorax

  • Air in the pleural space; partial or complete lung collapse; caused by trauma or lung disease.

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