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Histology > Lecture 27 > Flashcards

Lecture 27 Flashcards

1
Q

Respiratory portion of lungs

A

•Gas exchange

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2
Q

Conducting portion of lungs

A
  • 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
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3
Q

Epithelium type of various portions of upper respiratory tract

A

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

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4
Q

Conchae

A

Designed to make turbulence of air for air warming

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5
Q

Epiglottis

A

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

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6
Q

Vocal cords

A

Regions where there are muscles that narrow the gap where the air flows through, and we have high mechanical pressure.

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7
Q

Olfactory bulb and cribriform plate

A

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.

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8
Q

Olfactory epithelium

A

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.

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9
Q

Bowman’s glands

A

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.

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10
Q

How odorants are detected

A

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.

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11
Q

Olfactory knob

A

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.

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12
Q

Recognizing olfactory mucosa

A

From bottom to top: ethmoid bone, olfactory nerve fila, Bowman’s glands, olfactory epithelium (pseudostratified epithelium).

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13
Q

Structures in conducting vs respiratory portions of the lung

A

Conducting

  • trachea
  • main bronchus
  • lobar bronchus
  • segmental bronchus
  • terminal bronchiole

Respiratory

  • Respiratory bronchiole
  • Alveolar duct
  • Alveolar sac
  • Alveoli
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14
Q

Layers of epithelially lined tubes (inside to outside)

A

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)

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15
Q

Esophagus vs trachea lumen

A

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

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16
Q

Trachea layers - general

A

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
17
Q

Trachea layers - detailed

A

Respiratory epithelium containing goblet cells and cilia

Basement membrane (protects against bacterial invasion)

Lamina propria

Submucosa with submucosal glands

Perichondrium

Hyaline cartilage

Perichondrium

18
Q

Layers surrounding the trachealis muscle

A

Lumen of trachea

Respiratory epithelium: pseudostratified epithelium with cilia and goblet cells

Trachealis muscle

Esophagus epithelium: stratified squamous non keratinized epithelium

19
Q

Cells in respiratory epithelium

A

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

20
Q

Goblet cells

A

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

21
Q

Pleura of lung

A

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

22
Q

Breathing and gas exchange

A

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

23
Q

Intrapulmonary bronchus layers (outside to inside)

A

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

24
Q

Transition from trachea to alveoli

A

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

Histology (25 decks)

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