Lung Anatomy and Development Flashcards
How are the upper and lower lobes distinguished?
Divided by the oblique fissure
Upper and middle lobes are anterior
Lower lobe is posterior
Horizontal fissure
Creates the middle lobe on the right lung
Lingula
Part of the left upper lobe isolated by the cardiac notch
What is the benefit of separation of the lungs?
Lobe differentiation promotes uniform expansion
generally the lower lobe fills first, fissures allow the upper lobe to expand unimpeded
Cupola
Apex of the lung
Extending into the neck above the 1st rib
Hilum
Root of lung
Entry point for bronchi, pulmonary vein, nerves, etc
What are the primary, secondary and tertiary portions of the bronchial tree?
Main (primary) bronchus to each lung
Lobar (secondary) bronchus to each lobe
Segmental (tertiary) one for each broncho-pulmonary segment (10 of them forming the functional lung)
Carina
Tracheal bifurcation
Asymmetrical: right side is more vertical and likely to lodge objects, while left side is more horizontal because of the location of the heart
Where would you find the respiratory epithelium?
(pseudostratified ciliated columnar epithelium)
Extends from the nasal cavity, through the trachea and into the bronchioles
What are the three cell types found in the respiratory epithelium?
- Ciliated: form the mucociliary escalator; each cell has 250ish cilia sweeping mucus coat towards the mouth
- Mucus: (goblet) release mucin that adheres to particles; cells increase in number during chronic irritation
- Basal: replicate to replace epithelial cells
What makes up the trachea?
Mucosa, submucosa, cartilage rings, trachealis muscle, and adventitia
What is the mucosa?
Respiratory epithelium (ciliated and mucous cells) Lamina propria (CT)
What is submucosa?
Loose CT containing mucous glands and diffuse lymphatic tissue
What are cartilage rings?
C-shaped rings that maintain the patency of air Hyalin cartilage (chondrocytes in matrix) Avascular, but having a high concentration of glycosaminoglycans permits diffusion of fluid from blood vessels to chondrocytes
What is the trachealis muscle?
Smooth muscle attached to free ends of cartilage ring regulating wall tension
What is adventitia?
CT binding trachea to neighboring structures
What are bronchi made up of?
Mucosa + respiratory epithelium, basement membrane, muscularis mucosa + SM, submucosa + mucous glands, cartilage, discontinuous plates, adventitia
What are bronchioles made up of?
Mucosa: Resp. epithelium with simple columnar an cuboidal ciliated cells (fewer mucus cells)
Cartilage: not many; makes them susceptible to collapse with external pressure
Muscularis mucosa: extensive SM and elastic CT
What do terminal and respiratory bronchioles also have?
Clara cells: dome shaped, secrete lipoprotien preventing luminal adhesion if airway collapses and a secretory protein released during asthma
What do the terminal bronchioles feed into?
Secondary lobule: unit of tissue branching into several primary lobules forming polygonal patterns on the lung surface
What do the respiratory bronchioles feed into?
Acinus (primary lobule): unit containing alveolar ducts, sacs and alveoli where gas exchange occurs
What do type I alveolar cells form?
(pneumocytes) form most of the alveolar epithelium
What do type II alveolar cells do?
(pneumocytes) release surfactant and surfactant proteins
Surfactant
- Reduces surface tention and air-epithelium interface
- Prevents alveolar collapse with exhalation
- Post week 35, cells release DPPC
What do alveolar pores do?
Interconnect adjacent alveoli and equalize their pressures; permit bacterial passage for spread of infection
Alveolar macrophages
Ingest particulate matter
Can be found up bronchial tree in mucus, remain in local CT, of pass thru superficial and deep lymphatics into nodes
Summarize these tissue types in the bronchial tree:
- Ciliated Respiratory Epithelium
- Hyaline Cartilage
- SM
- Elastic Fibers
- extends into bronchioles
- extends only along trachea and bronchi
- extends into alveolar ducts
- universal, responsible for passive expiration
_______ branch continuously along the bronchial tree.
Pulmonary arteries
______ surround alveoli.
Capillaries
Two ______ from each lung drain venous blood into the _________.
Pulmonary veins……..left atrium
What do bronchial arteries carry form the aorta?
Oxygenated blood to the lung tissues
Describe pulmonary circulation in a bronchopulmonary segment
Pulmonary arteries follow bronchial tree to the center of the segment (carrying deoxygenated blood to alveoli)
Pulmonary veins and lymphatics follow intersegmental CT septa and carry oxygenated blood back to L. atrium
What is the vagus nerve impact on the lung?
(parasympathetic activity)
- Constricts bronchioles and activates glands
- Not very much innervation acts with locally released substances to increase bronchial constriction and mucus gland activation
What is the endocrine impact on the lung?
(sympathetic activity)
- Dilation of bronchioles
- EPI and NOREPI released from adrenal medulla act with slight innervation to dilate bronchioles by relaxing SM
What receptors regulate respiratory and behavioral reflexes?
Stretch, tactile, pain, baroreceptors, chemoreceptors, and tase receptors
How do bitter receptors cause bronchi dilation?
When exposed to saccharin, chloroquine and denatonium
- -> denatonium is the bitterest substance known and is added to alcohol or antifreeze to prevent consumption
- -> Chloroquine is an anti-malaria drug
What are pleura?
Bursa around the lung reducing friction in lung movement
Parietal pleura?
Adhere to thoracic cage, diaphragm and pericardium
Visceral pleura?
thin layer over lung surface
Pleural cavity?
space between parietal and visceral layers, cells secrete viscous fluid to increase lubrication
What is the costomediastinal recess?
Gap between the visceral and parietal pleural margins, where lungs expand during deep inspiration
What is the costodiaphragmatic recess?
Location for withdrawing lung exudates of air from the pleural cavity
What is pleurisy?
The inflammation of pleura that may lead to adhesions between pleural layers, limiting lung movement
What is pneumothorax?
Entry of air or fluid between the visceral and parietal pleura causing collapse of the lung (collapse as a result of their own elasticity)
How do ribs articulate with vertebrae?
Via hinge joints
- Costovertebral joints: head of rib articulates with facets on two adjacent vertebral bodies
- Costotransverse joints: tubercle of rib articulates with a TVP
How do ribs articulate with sternum?
Via costal cartilage
- Costosternal joints: ribs articulate with sternum via costal cartilages
- Sternomanubrial joint: sternal angle as a landmark for the 2nd rib
How does inspiration occur?
- required expansion of the thoracic cavity (raising ribs and lowering diaphragm)
- muscles that raise ribs: external intercostal, parasternal internal intercostal, SCM, scalenes
What does the hinge joint of the rib joints permit?
Permit ribs to swing upwards and outwards, increasing the anterior-posterior diameter and the transverse diameter
How do the external intercostal muscles raise the ribs?
- Muscles sloping down with the ribs (external intercostal) contract to raise them (like a shelf)
- Muscles sloping opposite to the ribs (posterior internal intercostal) pull down on the ribs and compress the space between
How does the diaphragm change rib cage diameter?
Increases vertical diameter via thoracic contraction by lowering the central tendon of the diaphragm
Phrenic nerve
- Motor nerve to the diaphragm
- passes anteriorly to anterior scalene (compression helps hiccups)
- below C5 spares phrenic nerve to permit unassisted breathing
What do phrenic nerve sensory neurons innervate?
Fibrous pericardium, pancreas and gallbladder
What does negative pleural cavity pressure refer to and how is it achieved?
- below atmospheric pressure
- raising the ribs and lowering the diaphragm
How does negative pressure of the pleural cavity cause lung expansion?
Negative pressure is a result of outward expansion of the thoracic wall exceeding the lungs’ elastic recoil.
Neg. pressure creates a pressure gradient and “suction”, whereby air is sucked into the lungs.
What is passive expiration?
Elastic recoil of the lungs, and relaxation of inspiratory muscles (intercostals, diaphragm..)
What is active expiration?
Internal (posterior) and innermost intercostal, as well as abdominals pull down on ribs reducing horizontal diameters.
Abdominal muscles contract and push diaphragm up.
Explain lung development
- Derived from the gut tube
- 5th week respiratory diverticulum branches from gut tube into bronchial buds
- One bronchial bud per lung, divide into the primary, secondary and tertiary bronchi
- Bronchioles are formed during weeks 17-26
Describe alveoli development
- mid 7th month-birth
- in the last month cuboidal cells of developing bronchioles flatten and become associated with capillaries and lymphatics
- herein respiration is made possible
- 90% of alveoli develop post-natally in the first 10 years
How do type II alveolar cells develop?
- Early 7th month when they start producing surfactant (lowers tension levels on the surface)
How do type I alveolar cells develop?
develop late from epithelial precurser cells or type II alveolar cells during the 7th month
What is the aspiration of amniotic fluid?
Fetal breathing movements that stimulate lung development and respiratory muscle conditioning
Where do lung buds develop?
Posterior to the heart, expanding into the rostral intraembryonic coelom (pericardioperitonial canal)
The _____ of the coelom separates from the _______.
Pleural part…….pericardium
Lung buds expand into the _______, forming the _____ and _____ layers of the ________.
coelom…..visceral and parietal…….pleura.
What develop from the esophagus?
Larynx and trachea as a ventral diverticulum
–> further divides into lung buds
What do the tracheo-esophageal folds form?
The folds fuse to the midline forming the tracheo-esophageal septum
What are tracheo-esophageal fistulas?
Common respiratory malformations, due to abnormal separation of the lung bud from the esophagus
–> can cause esophageal atresia with a tracheo-esophageal fistula
