Answer:
they give the lungs a really big surface area. they have moist, thin walls (just one cell thick) they have a lot of tiny blood vessels called capillaries.
The walls of the alveoli are only one cell thick. This makes the exchange surface very thin - shortening the diffusion distance across which gases have to move. Each alveolus is surrounded by blood capillaries which ensure a good blood supply.Adaptations of the alveoli:
Thin walls - alveolar walls are one cell thick providing gases with a short diffusion distance. Moist walls - gases dissolve in the moisture helping them to pass across the gas exchange surface. Permeable walls - allow gases to pass through.
Explanation:
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An agonist exhibit a positive biological effect similar to the receptor it stimulates. For instance, beta agonists (i.e. Salbutamol) stimulate the beta receptors in the bronchial system therefore leading to bronchodialtion. A competitive antagonist negates the function of the specific receptor by binding to the receptor binding site before the biological ligand. A non-competitive agonist negates the function of the specific receptor by binding to an allosteric site leading to a conformational change of the receptor site.
The question is incomplete. The complete question is:
Question: Select the correct statement about the special fetal blood vessels.
A The umbilical vein becomes the ligamentum teres.
B The distal parts of the umbilical arteries form the superior vesical arteries.
C The hepatic portal vein forms from the umbilical artery.
D The fossa ovalis becomes the f
oramen ovale.
Answer:
C) The umbilical vein becomes the ligamentum teres.
Explanation:
After birth, many vascular changes occur in the newborn child as the pulmonary, renal and digestive systems start functioning. As the umbilical cord is tied off and severed, the blood does not flow through the umbilical arteries. The umbilical vein in the child collapses but remains as the ligamentum teres. Ligamentum teres is a round ligament and serves to attach the umbilicus to the liver. It is present in the free border of the falciform ligament of the liver.
1) is right option. The fossils are an extinct specie of elephants, and they're related to present day elephants.
