Lecture 27 Flashcards
Respiratory portion of lungs
•Gas exchange
Conducting portion of lungs
- Air conduction: air goes to place where gas exchange occurs
- Air filtration: nose hairs, mucus in conducting portion to trap particles
- Air humidification: mucus
- Air warming: in nasal cavity, there is shelf-like structure called concha, which creates turbulence as the air flows inwards, giving air chance to be warm
- Speech: made by larynx
- Sense of smell
Epithelium type of various portions of upper respiratory tract
Nasal cavity: respiratory epithelium
Vestibule: stratified squamous non-keratinized epithelium
Olfactory mucosa: pseudostratified epithelium
Nasopharynx: respiratory epithelium
Oropharynx: respiratory epithelium
Larynx: respiratory epithelium
Vocal cords: stratified squamous non-keratinized epithelium
Trachea: respiratory epithelium
Conchae
Designed to make turbulence of air for air warming
Epiglottis
Air flows through nasopharynx into trachea, which is in front of the esophagus and it crosses the area where food comes in. Epiglottis has cartilage in it and closes trachea, so food does not go into trachea
Vocal cords
Regions where there are muscles that narrow the gap where the air flows through, and we have high mechanical pressure.
Olfactory bulb and cribriform plate
In humans, most of our odorant sensing epithelium is found at roof of nasal cavity.
An extension of the brain called OLFACTORY BULB is attached to a layer of bone surrounding the nasal cavity called CRIBRIFORM PLATE. Cribriform plate has openings where axons come from receptor cells that integrate into the OLFACTORY EPITHELIUM. These receptor cells send their axons into olfactory bulb, and then form olfactory nerves.
Olfactory epithelium
It is a pseudostratified epithelium. Olfactory epithelium has basal cells (that don’t reach the surface), supporting cell (reaches surface), receptor cells (aka olfactory cell)(supported by the columnar supporting cells) (reaches surface) (only a few hundred of receptor molecules can distinguish b/w diff odorants) and Bowman’s gland.
At the surface, olfactory receptor cells have cilia that protrude from the olfactory epithelium and are embedded into a mucus layer. Cilia are not motile, they increase SA for receptor molecules to bind odorants.
Bowman’s glands
Mucus is made by Bowman’s glands. These glands are located under ethmoid bone / cribriform plate and contained in the lamina propria under the ethmoid bone. The gland’s duct goes into the olfactory epithelium, and then into mucus layer.
How odorants are detected
Bowman’s Glands secrete olfactory mucus and Odorant Binding Protein. Supporting cells secrete Odorant Binding Protein.
Odorants get trapped in the mucus and get bound to the Odorant Binding Protein. Odorant Binding Proteins sequester the odorant trapped in the mucus and presents it to cilia on the olfactory receptor cells.
Once the olfactory receptor cells are stimulated, the signal is sent through
unmyelinated axons, which bundle right underneath the mucosa. The peripheral nerves are called olfactory nerve fila.
Olfactory knob
Olfactory receptor cells have knob-like apical extensions containing many cilia with odorant receptor molecules. The cilia along the apical surface of the cells are embedded in mucus.
Recognizing olfactory mucosa
From bottom to top: ethmoid bone, olfactory nerve fila, Bowman’s glands, olfactory epithelium (pseudostratified epithelium).
Structures in conducting vs respiratory portions of the lung
Conducting
- trachea
- main bronchus
- lobar bronchus
- segmental bronchus
- terminal bronchiole
Respiratory
- Respiratory bronchiole
- Alveolar duct
- Alveolar sac
- Alveoli
Layers of epithelially lined tubes (inside to outside)
Lumen (for air or food)
Mucosa
- epithelium
- lamina propria (loose CT)
- muscularis mucosa (smooth muscle)
Submucosa (DICT)
Muscularis externa (smooth muscle) (allows lumen to change size)
Adventitia (DICT)
Serosa (present when tube is suspended in body cavity)
Esophagus vs trachea lumen
Esophagus: folded lumen, with lots of changes in shape
Trachea: wide, open, smooth lumen; has horseshoe shape around trachea, which maintains the trachea and bronchi in an open configuration. This is hyalin cartilage
Both tubes run in parallel
Trachea layers - general
Lumen
Respiratory epithelium
Submucosa
- contains submucosal glands (aka seromucous) that make mucus and a protein-rich fluid, which are released into the lumen for lubrication
- brings blood vessels and nerves in
Hyaline cartilage
Adventitia
Trachealis muscle (smooth muscle) (muscularis externa)
- connects the horseshoe at the top
- allows flexibility
Trachea layers - detailed
Respiratory epithelium containing goblet cells and cilia
Basement membrane (protects against bacterial invasion)
Lamina propria
Submucosa with submucosal glands
Perichondrium
Hyaline cartilage
Perichondrium
Layers surrounding the trachealis muscle
Lumen of trachea
Respiratory epithelium: pseudostratified epithelium with cilia and goblet cells
Trachealis muscle
Esophagus epithelium: stratified squamous non keratinized epithelium
Cells in respiratory epithelium
Brush Cell: sensory cell, if there is an irritant that comes in, it can be sensed by brush cell. Brush cells are innervated with axons
Ciliated Cell: cilia move mucus and trapped particles towards pharynx. We swallow the material. This is cleansing action, which occurs all the time.
Basal Cell: are on basement membrane, do not reach apical surface. These are stem cells that replace dead cells.
Goblet Cell: make mucus to trap particles
Goblet cells
Goblet cells make mucin. There are glycoproteins in the RER at the base of the cell. Product goes through Golgi and is packaged into vesicles. Mucin granules are then exocytosed on the surface
In SEM, goblet cells protrude out of forest of cilia
Pleura of lung
Entire lung is surrounded by a bag of pleura (aka mesothelium). Pleura is a bag of epithelium that goes all around to the bronchus and is attached to diaphragm. Diaphragm moves up and down, making some friction. To protect lung and
lubricate, there is pleura that is filled with liquid. There is space that divides visceral (adjacent to lung) layer and parietal layer of pleura
Breathing and gas exchange
As you breathe in, we increase volume of lung and air enters. Then, gas exchange occurs, so the venous system carries oxygenated blood away from the lung
The pulmonary artery carries deoxygenated blood (contains CO2) into the lung where we have alveoli (thin wall air spaces for gas exchange).
Inhale/exhale is done by diaphragm and muscles surrounding conducting portion
of respiratory system
Intrapulmonary bronchus layers (outside to inside)
Alveoli
Hyaline cartilage
- The cartilage rings in the extra-pulmonary bronchus and trachea will break up into plates. The plates of hyaline cartilage are not complete rings anymore. The amount of cartilage decreases more and more as you go deeper into the lung. Hyaline cartilage does not completely surround lumen; there are bits and pieces of it.
Submucosa
- contains glands to lubricate the bronchi
Smooth muscle and elastic fibers
- Smooth muscle presses air out of lung via contraction. (All bronchi and bronchioles have smooth muscle performing this function)
- there is an increase of smooth muscle next to respiratory epithelium
- In addition to smooth muscle, there is lymphoid tissue containing accumulations of lymphocytes (sometimes can see lymphatic
nodule)
Folded mucosa
- respiratory epithelium
Lumen
Transition from trachea to alveoli
As the bronchus enters the respiratory portion, epithelium changes from pseudostratified to columnar cuboidal to
squamous in the alveoli
Goblet cells, glands and cartilage last appear in bronchus. Bronchioles do not have these.
Smooth muscle and elastic fibers remain all the way through
Ciliated cells last appear in terminal bronchioles
