Lecture 2 - Lower Respiratory System

Question 1

What parts of the resp. system are in the Lower respiratory system?

Answer 1

• Trachea
• Bronchi (R & L)
• Bronchioles
• Alveolar units

Question 2

What does the air-conducting tract in the LR system consist of?

Answer 2

• Trachea
• Bronchi
  
  • Primary (main)
  • Secondary (Lobar)
  • Tertiary (segmental)
• Bronchioles
  
  • Terminal bronchioles (No alveoli present)

Question 3

What does the respiratory tract in the lower respiratory tract consist of?

Answer 3

• Respiratory bronchioles (has alveoli unlike terminal bronchioles)
• Alveolar units

Question 4

Describe the trachea

• It’s structure
• The Cartilage arrangement
• What muscle lies posteriorly in between the C-shaped cartilage
• What kind of tissue lies between the adjacent cartilage bars

Answer 4

The lumen of the trachea is D shaped in transverse section

It’s made of 15-20 C-shaped cartilages which maintain the patency of the airway.

Posteriorly in the gaps between the C shaped cartilage lie bundles of smooth muscle called Trachealis muscle

Between the adjacent bars of cartialge the narrow gaps are filled by fibrous connective tissue called annular ligaments, which also contain numberous elastic fibres to give elasticity to the wall

Question 5

Where is the thyroid gland located?

Answer 5

In front of the upper cartilage rings and at the sides of the trachea

Question 6

Describe where the trachea extends from, and how it terminates

Answer 6

The trachea extends from C6 to T4 level inferiorly and is about 10cm in expiration (& postmortum), and on inspiration extends to T5-6 level inferiorly (with 15cm in length).

The trachea terminates by dividing (tracheal bifurcation) into left and right main bronchus at the level of the imaginary plane between the sternal angle & T4

The carina is a ridge of cartilage in the trachea that occurs in the lumen at the tracheal bifurcation.

Question 7

Describe the bronchi divisions

Answer 7

1. There’s 2 (main) bronchi (left and right) divide into 3 secondary (lobar) bronchi on right and 2 secondary (lobar) bronchi on the left (One for each lobe of the lung).
2. The secondary (Lobar) bronchi divide into tertiary (Segmental) bronchi - one for each bronchopulmonary segment in the lobe.
3. The tertiary (Segmental) bronchi divide to give progressively smaller and smaller tubes - the bronchioles

Question 8

Which bronchi are intrapulmonar and extrapulmonar?

Answer 8

Right main bronchus, left main bronchus and right superior lobar bronchus are extrapulmonary; all other bronchi are intrapulmonary

Question 9

Compare the extrapulmonary bronchi structure to that of the trachea

Answer 9

Extrapulmonary bronchi structure closely resember that of the trachea - and only differ from it by having a smaller diameter with cartilage rings still incomplete, posterior deficiency is still occupied by smooth muscle and still has D-shaped lumen.

Question 10

Compare the structure of the intrapulmonary bronchi to the trachea

Answer 10

Intrapulmonary bronchi differ from the trachea alot more than extrapulmonary bronchi.

They are spherical in outine, and don’t show posterior flattening which is seen in trachea or C-shaped cartilage rings.

The cartilage is arragned into irregular plates and the smooth muslce fibres are arranged in spirals around the bronchus, together with elastic fibres.

Question 11

Answer 11

Label this

Question 12

Label this my g

Answer 12

Question 13

A conducting tube of less than 1mm diameter is regarded as a _______

Answer 13

Bronchiole

Question 14

Describe the changes seen in cilia, goblet cells and submucosal glands when moving further down towards the bottom of the respiratory tree

Answer 14

Cilia extend further down the respiratory tree than do goblet cells and submucosal glands, thus preventing the respiratory tissue from becoming waterlogged or occluded by mucus.

In the smallest bronchioles where cilia are absent, macrophages take over the function of internal drainage

Question 15

Describe the terminal bronchioles

Answer 15

They are narrowest part of the air-conducting system, which has cuboidal epithelium with no goblet cells, and has only patches of ciliated cells. It is surrounded by respiratory tissue.

Question 16

Describe the respiratory bronchioles

Answer 16

Contains alveoli on their wall, so therefore they are not apart of the air-conducting system, but are the first component of the respiratory system (=gaseous exchange) where blood in capillaries is seperated from air with a very thin mass of material so that they can exchange CO2 & O2. This arrangement occurs in the respiratory bronchioles to alveoli.

Question 17

Answer 17

Question 18

Describe how respiratory bronchioles eventually form the alveoli

Answer 18

Respiratory bronchioles branch into alveolar ducts.

(Alveolar ducts are thin walled tubes which connect the respiratory bronchioles to alveolar sacs)

The alveolar duct opens to an alveolar sac, each of which contains a collection of alveoli (small pouches made of flattened epithelial cells that allow gas exchange)

Question 19

What is an acinus?

Answer 19

A pulmonary acinus comprises the distal unit that contains gas-exchange surfaces of the lung in the form of respiratory bronchioles, alveolar ducts and alveoli.

An acinus contains these three structures

Question 20

What occurs at the air-blood barrier? (resp. membrane)

Answer 20

Gas exchange occurs when CO2 in blood (carried to the lungs in pulmonary arteries) diffuses across the blood capillary wall into the alveoli, and O2 diffuses from the air in the alveoli acorss the capillary wall into the pulmonary veins. The oxygenated blood returns via the pulmonary veins to the left atrium of the heart.

The layers of tissue that constitute the gas exchange is called the air-blood barrier (Respiratory membrane).

Question 21

How do the lungs stay in their position in the thoracic cavity?

Answer 21

They lie free in the thoracic cavity except where they are attached by their roots to the heart and trachea.

Question 22

Describe the shape of the lungs

Answer 22

They are conical in shape with apex, base and 3 surfaces

Apex = upper tapered part (lies in the plane of thoracic inlet)

Base = Concave, lower part (overlies the dome of the diaphragm)

Surfaces are costal, diaphragmatic, medial

Question 23

What are the surfaces of the lungs?

Answer 23

• Costal - is convex and fits the thoracic wall formed by the sternum, ribs and costal cartilages
• Diaphragmatic - is concave and fits the domeof diaphragm
• Medial - is divided into
  
  • Mediastinal part which shows a concavity caused by the heart and pericardium (Cardiac impression)
  • Vertebral part in contact with the sides of thoracic vertebrae

Question 24

Label this

Answer 24

Question 25

What are the borders of the lungs?

Answer 25

**Anterior -** seperates costal and medial surfaces **Inferior -** seperates diaphragmatic from costal and medial surfaces **Posterior -** seperates costal and (vertebral part of) medial surface

Question 26

Where can you find the hilum, and what does it contain?

Answer 26

Found on the **medial surface,** **above and behind cardiac impression** is a depression. It contains: * Blood vessels * Lymphatic vessels * the nerves * the bronchi Entering or leaving the lung. These structures form the **root** of the lung.

Question 27

Label these structures which pass through the hilum

Answer 27

Question 28

Describe how the left and right lung is divided into lobes, and name of the fissures etc Which lung has specific features, and what are they called?

Answer 28

**Left lung** is divided into two lobes by an oblique fissure to give **upper** and **lower lobes.** **Cardiac notch** and **lingula** are the **specific structures (only found in left lung)** The **right lung** is divided into **3 lobes** by **2 fissures.** An **oblique fissure** seperates the **upper** and **middle lobes** from **lower lobe.** And a **horizontal fissure (aka transverse fissure)** seperates the lower lobe from the middle lobe. NO specific structures.

Question 29

Which lung is this, and label it

Answer 29

Question 30

Which lung is this, and label it

Answer 30

Question 31

Describe how each lobe is further subdivided, and what each segment is supplied and drained by

Answer 31

Each lobe is further subdivided into **segments** (Called **pulmonary** or **bronchopulmonary segments)** Each segment is supplied by * A segmental bronchus * A branch of the pulmonary artery * A branch of a bronchial artery And drained by * a tributary of the pulmonary vein * a tributary of a bronchial vein * lymphatic vessels

Question 32

What are bronchopulmonary segments?

Answer 32

A bronchopulmonary segment is the **smallest, functionally independent region** of a lung and the smallest area of lung that can be isolated and removed without affecting regions (making it **surgically resectable).**

Question 33

Describe the path of the bronchiole arteries, and how this it's blood is drained

Answer 33

They travel and branch with the brocnhi, terminating at the level of the respiratory bronchioles (therefore aren't associated with gaseous exchange). Most of the blood supplied by the bronchial arteries are returned via **the pulmonary veins** rather than the bronchial veins. The blood from the first few divisions of bronchi is drained by **bronchial veins** to veins of the posterior thorcacic wall (azygous, hemiazygous, or posterior intercostal veins).

Question 34

Compare and contrast the function, circulation , and diameter of the pulmonary arteries with bronchial arteries

Answer 34

Question 35

Where do the bronchial arteries branch from?

Answer 35

The aorta

Question 36

How is the lymph in the lungs drained?

Answer 36

Lymph is drained to * Pulmonary nodes (within the lung) * Bronchopulmonary nodes (located at hilum) * Inferior tracheobronchial nodes (in angle of division of trachea) * Superior tracheobronchial nodes (alongside trachea) And is carred in **_R and L bronchomediastinal trunks_** to the **R lymphatic trunk** and **thoracic duct which then joins the systemic venous system**

Question 37

Where are the pulmonary plexuses located?

Answer 37

Located in **close proximity to the root of the lung**

Question 38

Where do the postsynaptic **sympathetic fibres** arise from to reach the pulmonary plexuses?

Answer 38

From the upper 3 or 4 thoracic sympathetic ganglia to reach the pulmonary plexuses

Question 39

Where do the presynpatic **parasympathetic fibres** (carried in **\_\_\_\_\_** nerve) come from?

Answer 39

Comes from the medulla carried in the **vagus nerve.** They synapse with parasympathetic ganglion cells present in the pulmonary plexuses along the bronchial tree.

Question 40

How does sympathetic activity affect the diameter of bronchi, secretion, and vascular tone of pulmonary vessels

Answer 40

Question 41

How does parasympathetic activity affect the diameter of bronchi, secretion, and vascular tone of pulmonary vessels

Answer 41

Question 42

What two types of visceral afferet fibres are there in the pulmonary plexus

Answer 42

**Reflexive** (conducting subconscious sensations associated with reflexes that control function) OR **Nociceptive** (conducting pain impulses generated in response to painful or injurious stimuli such as chemical irritants, ischaemia, or excessive stretching)