Answer: Nerve cells and muscle cells are excitable because their cell membrane can produce electrochemical impulses and conduct them along the membrane.
Explanation:
It makes the Earth livable for us creatures. We get protected from the Sun's harmful rays reaching to Earth, which makes Earth feel comfortable. Atmosphere also contains Oxygen and we rely on that everyday.
The acetabulum is shaped developmentally by three bones
namely ilium, ischium, and pubis. As associated with the glenoid cavity of the
scapula, it is focused inferiorly other than laterally and anteriorly, is
deeper, and is not enclosed wholly by the articular cartilage (but solitary on
a lunate surface). The hip joint is become constant primarily by its capsule
and ligaments, the shoulder joint by the musculotendinous cuff.
Diffusion is one form of passive transport that doesn't require the expenditure of cellular energy. A molecule can diffuse passively through the cell membrane if it's lipid-soluble, uncharged, and very small, or if a carrier molecule can assist it. ... The assisted process is known as facilitated diffusion.
Got this off google but still hope it helps :)