Exam 3 Review:  Chapter 22:  Alveoli

Follow this link for images of alveolar anatomy.

alveolar duct - The terminal branch(es) of each respiratory bronchiole in the lungs, lined by a simple squamous epithelium, which deliver inspired air to the alveolar sacs.

alveolar sac - A cluster of alveoli located at the end of each alveolar duct in the lungs; each of the alveoli is a tiny, thin-walled, capillary-rich sac, lined by a simple squamous epithelium, where the exchange (diffusion) of oxygen and carbon dioxide (and other less important gases) takes place.

alveolus - (1)  A tiny, thin-walled, capillary-rich sac in the lungs, lined by a simple squamous epithelium, where the exchange of oxygen and carbon dioxide (and other less important gases) takes place; the approximately 300 million alveoli have a total cross-sectional area of 50- 70 m2, which equals ~40 times the surface area of the skin.  aka - air sac  (2)  A tooth socket in the jawbone.

type I alveolar cell - The squamous epithelial cell forming the alveolar wall and through whose cell membranes and cytoplasm the exchange of oxygen and carbon dioxide (and other less important gases) takes place; collectively they cover 95% of the alveolar surface area.

type II alveolar cell - The cuboidal cell found as a minor component of the alveolar wall, they are scattered among the type I cells and account for only 5% of the alveolar surface; they have three main functions:  (1) secretion of surfactant, (2) control of alveolar fluid levels by water recapture using active sodium transport to return excess alveolar surface water to the interstitial fluid, and (3) the stem or progenitor cell which can proliferate to replace both type I and type II cells after injury.

alveolar macrophage = dust cell - The large mobile cell, derived from the monocyte, occurring in low numbers within the connective tissue of the alveolar walls and, more commonly, patrolling on the walls of the alveoli, which ingests by phagocytosis any foreign particles and infectious microorganisms which reach the alveoli; they may also transport indigestable materials such as soot or silica dust to the lymph nodes of the lungs for storage.

alveolar-capillary membrane = respiratory membrane - The collective term for all the structural components through which respiratory gases must diffuse in order to be exchanged between the air in the alveoli and the blood; this consists of the cell membranes and cytoplasm of the type I alveolar cells, the alveolar epithelial basement membrane, the very limited amount of loose fibrous connective tissue present, if any, beneath it, the capillary basement membrane, and the cell membranes and cytoplasm of the capillary endothelial cells.

alveolar wall - The anatomical term for all the structural components through which respiratory gases must diffuse in order to be exchanged between the air in the alveoli and the blood; this consists primarily of the type I alveolar cells (a minority of the type II alveolar cells and alveolar macrophages are also present), the alveolar epithelial basement membrane, the very limited amount of loose fibrous connective tissue present, if any, beneath it, the capillary basement membrane, the capillary endothelial cells, and the blood passing through the capillaries.

epithelial basement membrane - The thin microscopic network of fibrous proteins synthesized by the basal layer of any epithelial tissue which forms a physical foundation and a physiological barrier between the epithelial tissue and the underlying connective tissue.

capillary basement membrane - The thin microscopic network of fibrous proteins synthesized by the endothelial cells of capillaries which forms a physical foundation and a physiological barrier between the endothelial cells and the underlying tissue.

endothelial cell - Any of the simple squamous cells which form a single layer and line the walls of the heart, blood vessels, and lymphatic vessels; this tissue arises from mesoderm.

simple squamous epithelium - Tissues with a high degree of cellularity and limited extracellular material, connected with specialized contact structures such as desmsomes, organized in a single layer in which the cells present are flattened (cells wider than they are tall with reference to the basement membrane), which have no direct blood supply and which are derived from embryonic ectoderm or endoderm.

surface tension -  That property, due to unbalanced molecular cohesive forces, which exists in the surface film of all liquids and tends to bring the contained volume into a form having the least superficial area and where the surface tends to contract and has properties resembling those of a stretched elastic membrane; the thickness of this film, amounting to less than a thousandth of a millimeter, is considered to equal the radius of the sphere of molecular action, that is, the greatest distance at which there is cohesion between two particles; particles lying below this film, being equally acted on from all sides, are in equilibrium as to forces of cohesion, but those in the film are on the whole attracted inward, and tension results.  See diagram below.

List:

5.  The four factors that affect pulmonary gas exchange (external respiration) across the respiratory membrane.

          (1)  the surface area, thickness, and other structural components of the moist respiratory membranes available for gas diffusion
          (2)  the partial pressures of the gases oxygen and carbon dioxide in the alveloar air
          (3)  the gas solubilities (solubility coefficients) of the gases oxygen and carbon dioxide
          (4)  the physiological relationship between ventilation (bulk air movements into and out of the alveoli) and perfusion (bulk flow of blood through the alveolar capillary beds)


6. The five cell types found in the walls of an alveolus and a function for each cell.

Cell Type Found in the Alveolar Wall Function(s)
type I alveolar cell  form the alveolar wall (95%) and permit gas exchange
type II alveolar cell (1) secretion of surfactant, (2) control of alveolar fluid levels by water recapture using active sodium transport to return excess alveolar surface water to the interstitial fluid, and (3) the stem or progenitor cell which can proliferate to replace both type I and type II cells after injury
alveolar macrophage = dust cell phagocytosize any foreign particles and infectious microorganisms which reach the alveoli; they may also transport indigestable materials such as soot or silica dust to the lymph nodes of the lungs for storage
capillary endothelial cell form the capillary wall and permit gas exchange
erythrocyte = RBC essential for oxygen transport and, to a lesser degree, carbon dioxide transport within the blood

Sketch and label:

1. The respiratory membrane. Describe the kinds of cells that make up this membrane and their functions.

Describe the kinds of cells that make up this membrane and their functions.
Cell Type Found in the Alveolar Wall Function(s)
type I alveolar cell  form the alveolar wall (95%) and permit gas exchange
type II alveolar cell (1) secretion of surfactant, (2) control of alveolar fluid levels by water recapture using active sodium transport to return excess alveolar surface water to the interstitial fluid, and (3) the stem or progenitor cell which can proliferate to replace both type I and type II cells after injury
alveolar macrophage = dust cell phagocytosize any foreign particles and infectious microorganisms which reach the alveoli; they may also transport indigestable materials such as soot or silica dust to the lymph nodes of the lungs for storage
capillary endothelial cell form the capillary wall and permit gas exchange
erythrocyte = RBC essential for oxygen transport and, to a lesser degree, carbon dioxide transport within the blood