Sudoriferous and Sebaceous glands in Mammals, Hydrostatic skeleton and Amoeboid movement
Sudoriferous and Sebaceous glands in
Mammals:
Sudoriferous
glands: Sudor = sweat. They are also called sweat glands and are distributed
over most of the human body surface. These glands secrete sweat by a process
called perspiration. Perspiration helps to regulate body temperature and
maintain homeostasis, largely by the cooling effect of evaporation. In some
mammals curtain sweat glands also produce pheromones (it is a chemical that an
animal secretes and that communicates with other members of the same species to
elicit certain behavioural responses).
Sebaceous
glands: They are oil glands. They are simple glands connected to hair follicles
in the dermis. They lubricate and protect by secreting sebum. Sebum is a
permeability barrier, an emollient (skin softening agent) and a protective
agent against micro organisms. Sebum can also act as pheromone.
Hydrostatic skeleton:
Skeleton of
invertebrates is a core of liquid (water or a body fluid such as blood)
surrounded by a tension resistant sheath of longitudinal or circular muscles.
It is similar to water filled balloon because the force exerted against
incompressible fluid in one region can be transmitted to their regions.
Contracting muscles push against hydrostatic skeleton and the transmitted force
generates body movements as the movement of sea anemone. Lumbricus (earth worm)
contracts its longitudinal and circular muscles alternately creating a rhythm
that moves the earthworm through the soil. In both the hydrostatic skeleton
keeps the body from collapsing when its muscles contract. Invertebrate
hydrostatic skeleton can take many forms and shapes such as gastrovascular
cavity of acoelomates, a rhynchocoel in nemertines, a pseudocoelom in aschelminthes, a coelom in annelids or a
hemocoel in molluscs.
Amoeboid movement:
Plasma membrane
of amoeba has adhesive properties since new pseudopodia attach to the substrate
as they form the plasma membrane. A thin fluid between plasma membrane and
ectoplasm facilitate this sliding. As amoeba moves, the fluid endoplasm flows
forward into the fountain zone of advancing pseudopodium. As it reaches the tip
of a pseudopodium, endoplasm changes into ectoplasm. At the same time,
ectoplasm near the opposite end in the recruitment zone changes into endoplasm
and begins flowing forward.
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