histology

Question 1

what does the naval cavity do?

Answer 1

warms, moistens and filters the inspired air

Question 2

what is the nasal cavity (the vestibule) lined with?

Answer 2

initial part - keratinised stratified squamous epithelium
deeper - the keratin is lost
even deeper - pseudostratified ciliated columnar epithelium with goblet cells, also called respiratory epithelium

Question 3

why must the oropharynx resist abrasion?

Answer 3

• because it transmits both air and food
• lined by non-keratinised stratified squamous epithelium as is the anterior surface and upper part of the posterior surface of the epiglottis

Question 4

what are the larynx walls made of?

Answer 4

• cartilage and muscles with respiratory epithelium lining it’s surfaces
• exception of the vocal folds and adjacent structures, which are covered with stratified squamous epithelium

Question 5

what is the trachea?

Answer 5

• it is continuous with the larynx and terminated by dividing into the main bronchi
• it contains 15-20 C shaped cartilages
• the open side of the C is spanned by fibroelastic tissue and smooth muscle (trachealis muscle)

Question 6

what is the trachea lined with?

Answer 6

• walls = respiratory epithelium back by a basal lamina, a lamina, a lamina propria of connective tissue with abundant elastic fibres and a submucosa of connective tissue that includes numerous seromucous glands

Question 7

what is the bronchi?

Answer 7

• it divides into 2 main primary bronchi = these divide further
• the rings of hyaline cartilage are replaced by irregularly shaped cartilage plates
• the wall is made of respiratory epithelium, a lamaina propria, a muscularis consisting of a ring of smooth muscle and a submucosa with adipose tissue and some seromucosa glands

Question 8

what happens as the bronchi branches become smaller?

Answer 8

they cartilage is lost when they are under 1mm, now called bronchioles

• the epithelium decreases in height from columnar to cuboidal as you progress down the respiratory tree to the smallest bronchioles
• the lamina propria is composed of smooth muscle and elastic and collagenous fibres

Question 9

what are the terminal bronchioles?

Answer 9

• the smallest bronchioles that lack respiratory function
• they branch to give rise to the first part of the respiratory tree that as respiratory function, these are called the respiratory bronchioles

Question 10

what do the smooth muscle of the bronchioles respond to?

Answer 10

• parasympathetic innervation and histamine

- plays a significant role is asthma attacks and allergic reactions

Question 11

what are terminal bronchioles lined with?

Answer 11

• cuboidal ciliated epithelium

- they contain non-ciliated club cells that project abouve the level of adjacent ciliated cells

Question 12

what are the roles of club cells?

Answer 12

• stem cells
• detoxification
• immune modulation
• surfactant production

Question 13

what happens when the alveoli interrupts the continuity of the respiratory bronchioles?

Answer 13

the low cuboidal epithelium is replaced by discontinuous squamous type 1 alveolar cells

Question 14

does oxygen/co2 exchange occur from the trachea to the terminal bronchia?

Answer 14

no, but gas exchange does occur in the alveoli

Question 15

where are alveoli found?

Answer 15

in the terminal portions of the bronchial tree

Question 16

what are alveoli responsive for?

Answer 16

• the spongy nature of the lungs

- gas exchanged here

Question 17

what are alveoli lined with?

Answer 17

• epithelium that consists of type 1 and type 2 alveolar cels = pneumocytes

Question 18

what are type 1 alveolar cells?

Answer 18

• simple squamous epithelium that lines the alveolar surfaces
• these provide a barrier of minimal thickness that is permeable to glass

Question 19

what are type 2 alveolar cells?

Answer 19

• polygonal in shape
• the free surface is covered by microvilli and the cytoplasm displays dense membrane bound lanellar bodies which contain surfactant
• the surfactant is release by exocytosis ad spreads over the pulmonary surface ti reduce the surface tension at the air-fluid interface
• this reduces the tendency fir the alveoli to collapse at the end of expiration

Question 20

what are alveolar macrophages?

Answer 20

• free cells either in the septa r migrating over the luminal surfaces of the alveoli, phagocytosing inhaled particles that may have escaped the mucous
• the migrated up the bronchial tree
• are transported by ciliary action to the pharynx where they are swallowed or will move into the septal connective tissue where they will remain

Question 21

what does the air-blood barrier consist of?

Answer 21

type 1 cells, the endothelial cells and the basal lamina of each

Question 22

what is the lung surrounded by?

Answer 22

• visceral pleura that is multi-layered
• there is an outer layer of simple squamous epithelium called mesothelium backed by layers of fibrous and elastic connective tissue
• this faces the partial pleura
• between the two would be a pleural cavity containing a small amount of lubricating fluid