THE HUMAN BODY
By Rachel Bull
The organelles of cells and their
• Cell (or plasma) membrane - The plasma membrane
acts as a boundary and controls what substances can
enter and exit the cell.
• Cytoplasm - This semi-fluid substance found inside the
boundary of the cell and outside the nucleus cushions
and protects the internal organelles, this is also where
the majority of the chemical reactions happen.
• Nucleus - The nucleus is the double-membraned central
part of the cell that contains and carries DNA strands
and controls what happens inside the cell.
• Nucleolus - The nucleolus is found in the dense region
of the nucleus, it plays an essential role in the
formation of ribosomes.
The structure of the cell membrane
• Mitochondria - The mitochondria are spherical or
rod-shaped bodies that are scattered in the semifluid cytoplasm and are considered the 'powerhouse' of the cell as it aids ADP (adenosine triphosphate)
• Smooth ER - The smooth endoplasmic reticulum has
no attached ribosomes and is responsible for
synthesizing lipids and some carbohydrates within
the cell network.
• Rough ER - Unlike the smooth endoplasmic
reticulum the rough endoplasmic reticulum has
ribosomes present along its membrane from which
is receives and transports synthesised proteins.
• Golgi Apparatus - A series of flattened fluid-filled
sacs that chemically process, then package
substances from the ER and is involved in secretion
and intracellular transport.
• Lysosome - The lysosomes are known as the
'digestive system' as they can digest all major
chemicals in living cells, they are enclosed by a
TISSUES OF THE
Epithelia are the linings of external and internal surfaces and body cavities, including ducts (channels or tubes) carrying secretions from glands. They are composed of several layers of cells, called compound epithelia, or a single layer known as simple epithelia. The bottom or lowest layer of cells is attached to the basement membrane to provide support and connection. Some parts of the basement membrane can be secreted by the epithelial cells. There are nerve supplies to the epithelia but they're supplied with nutrients and oxygen from deeper tissues by diffusion. The surface tissues are often exposed to friction, therefore, the capacity for growth and repair is much greater than other tissues and this normally occurs during sleep.
Simple epithelial cells may be cuboidal, ciliated, columnar or squamous. • Squamous epithelial cells are very flat and each nucleus forms a lump at the centre. The cell is very flat and fits together with other cells very closely. As they are so thin and delicate they don't offer much protection.
• Cuboidal epithelial cells have a spherical nuclei and are cube-shaped. The allows material to pass through in a similar way to diffusion and they often line ducts and tubes.
• Columnar epithelial cells have a slightly oval nuclei and are much taller than other simple epithelia. They are often associated with cilia and are then named ciliated epithelia.
The function of compound epithelia is to provide protection to deeper structure. Compound epithelia has multiple layers of cells. The vagina, tongue, oesophagus and mouth are lined by cells that are superficial and not keratinised. The skin is built up of outermost cells that have died and become hard due to deposition of keratin.
Simple squamous epithelium
Simple cuboidal and columnar epithelial
Section through stratified epithelium
Blood – Blood is a liquid matrix with flowing red and while cells that is found in the blood vessels.
Cartilage – Cartilage is a flexible but hard bone structure found in the nose, external ear and surface of bones.
Bone – Bones are hard calcified background materials in...
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