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Nuclei are found in all
cells, except red blood cells, this is as it allows them to contain more hemoglobin.
The nucleus itself consists of a nuclear envelope, which is a double membrane
that controls the entry and exit of materials (due to the nuclear pores within
it), ad controls the reactions taking place within, the outer membrane of this
is continuous with the rough endoplasmic reticulum (RER). Within this consists
of chromosomes, a protein bound linear type of DNA, which is surrounded by
nucleoplasm, granular jelly like material that gives bulk to the nucleus.

The ER is a system of
sheet like membranes that spread through the cytoplasm (another jelly like
substance that gives the nucleus its shape and contains many different
components). The membranes that link the RER and the nucleus enclose tubules of
flattened sacs called cisternae. The second type of ER, the smooth endoplasmic
reticulum (SER) doesn’t have proteins on its surface like the RER does,
synthesises, stores and transports lipids and carbohydrates.

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The cell membrane present
controls what goes in and out of the cell, mostly it allows substances like
oxygen and some nutrients into the cell, as it is a semi permeable membrane.

Similar to the ER in
structure, the Golgi Apparatus is more compact and especially well developed in
epithelial cells. Its main features are the cisternae which are sac like
structures, and the vesicles which are round and hollow in structure. The job
of the golgi is to modify proteins and lipids that the ER send over by adding
components that are not made of protein, such as carbohydrates. The golgi then
sends the modified proteins to their correct destinations using golgi vesicles
as a transport system, to cell surfaces where they will be fused with the
membrane and their contents will be released outside of the cell.

When vesicles
from the golgi contain enzymes such as proteases and lipases, lysosomes a
formed. Lysosomes remove harmful waste material from the cell, usually they
contain lysozymes, these are enzymes that hydrolyse cell walls of bacteria.
Lysosomes have the ability to isolate up to fifty enzymes from the rest of the
cell before releasing them to the outside or into a phagocyte vesicle within
the cell.

release energy within the cell. The mitochondria is made from a double membrane
that controls the entry and exit of material, the inner membrane of this is
folded to form cristae. Cristae provide a large surface area for the attachment
of enzymes and proteins for respiration. The matrix makes up the
remainder of the mitochondrion, it contains proteins, lipids, ribosomes and DNA
that allows the mitochondrion to control the production of some of their own



Tissues are a group of
similar cells that work together to perform a specific task. There are four
types of tissue in the body:


The role of muscular tissue
depends on what type of muscular tissue it is and where in the body it is
found, but in general this type of tissue is essential for keeping the body
upright, allowing the body to move, pump blood and push food through the
digestive tract. – (c2017) What is a Human Body Tissue? Available
at (Accessed 15/01/18).

In accordance to, “the muscles found in the body
of every dog are composed of a mass of cells held together by connective
tissues. Connected to the skeletal system, skin, and other muscles, each muscle
in the body helps to create movement. Muscle fibers in a dog’s body receive
electrical impulses from the brain via the central nervous system. These
impulses are converted into a form of mechanical energy in muscles that forces
it to contract, thereby producing movement.” –
(c2018) The Muscle Anatomy of a Dog. Available at
(Accessed 15/01/18). This information goes to show the vast amount of
structures involved in everyday movement, in which all of these structures need
to work in accordance to each other to provide a well-functioning body; no
matter what the animal.

are three main types of muscle: skeletal muscle, cardiac muscle, and smooth
muscle. Skeletal muscle is attached to bones by tendons (elastic tissue fibers),
and it allows you to consciously control your movements – this is known as a
voluntary movement.

movement is due to the cardiac muscle. It is only found in the walls of the heart,
and like skeletal muscle, cardiac muscle is striated, or striped (why?) , not only this, it
is elongated and branched (why?)
and is in constant work. Its individual fibers are connected by structures
called intercalated disks, which allow them to contract in sync (why is this needed?).

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