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How the Human Body Works: An Introduction

Paper Type: Free Essay Subject: Biology
Wordcount: 4200 words Published: 31st May 2018

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  • Lisa Rann

Light Microscope

Electron Microscope

How they work

A light ray is beamed from a source beneath the specimen and transmitted through the objective and ocular lenses to produce a focused colour image on the retina of the eye when viewed through the eyepiece.

Specimen is mounted in a vacuum and coated in a thin layer of metal to reflect the electrons. In the Transmission Electron Microscope (TEM), an electron beam is transmitted through the specimen and focussed to form a black and white image on a fluorescent screen. In the Scanning Electron Microscope, a fine beam of electrons is scanned onto the surface of the specimen and the electrons scattered by the surface are collected to form a 3D image of the surface, on a fluorescent screen, with poorer resolution than the TEM.


Lower magnification, can magnify up to 1,500 x after which image clarity is lost.

Higher magnification, can magnify 500,000 x.


Lower resolution- around 200nm.

Higher resolution- around 0.05nm.


Lower, due to lower resolution -limited by the wavelength of light.

Higher. The electron beam has a shorter wavelength than light.


Can be used in educational settings, by hobbyists or in hospitals to observe living processes such as cell division.

Usually found in large laboratories, can only observe dead specimens.


Relatively inexpensive

Extremely expensive.

Word Count: 220


www.areallygoodread.com. (2014).Light Microscopes and Electron Microscopes.Available: http://www.areallygoodread.com/technology-and-science/light-microscopes.aspx. Last accessed 26/06/2014.

Microbehunter. (2014).Electron Microscopes vs Optical (light) Microscopes.Available: http://www.microbehunter.com/electron-microscopes-vs-optical-light-microscopes/. Last accessed 03/07/2014.

Monger G. Roberts M. & Reiss M. (2000).Advanced Biology. London: Nelson. 48-49.




Function of organelle


Found in the nucleus of the cell and condenses into chromosomes, which carry the DNA when the cell undergoes division. In cells which are not dividing, the Chromatin appears as a diffuse granular mass.

Rough Endoplasmic reticulum

Involved in the manufacture and transport of material to other locations, such as proteins, antibodies and insulin. The rough ER and smooth ER are usually connected. The rough ER has ribosomes attached to the cytoplasmic side of the membrane. It is shaped this way to provide a large surface area for chemical reactions.

Smooth Endoplasmic reticulum

Acts a storage organelle, involved in the production and storage of steroids, lipids and ions. Also has a detoxification function and is a membranous network of folded, smooth tube like sacs – shaped this way to provide a large surface area for the chemical reactions.

Golgi apparatus

Acts as the assembly factory for newly synthesised proteins passing from the channels of the rough endoplasmic reticulum, having carbohydrates added to them, being enveloped and leaving the cell. Composed of flat sacs called Golgi Cisternae, often curved and give it a cuplike shape. Most cells have several Golgi Apparatus and they are more common in cells which secrete protein.


A drawn out elongated hair like structure which primarily acts as a method of locomotion in the cells of living organisms. It is long and generates a forward motion by rapidly moving in a wave like pattern and is shaped like this to help it move – such as the tail of a sperm cell.


Generate the energy the cell needs to do its job. The wall of the mitochondrion consists of two thin membranes, the outer and inner mitochondrial membranes, between them is a small fluid filled space. The inner membrane contains the large central fluid filled matrix and cristae which is a membrane with a series of folds which provides a large surface area for the mitochondria to perform the chemical reactions which are part of aerobic respiration with the synthesis of ATP.


Contains a eukaryotic cell’s hereditary information and controls the cell’s growth and reproduction. A double membrane, the nuclear envelope separates the nucleus from the cytoplasm, both layers of the envelope are lipid bilayers and nuclear pores control the movement of substances between the nucleus and the cytoplasm.


Single membrane enclosed vesicles that form in the Golgi Complex and contain hydrolytic digestive enzymes. Have spherical bodies and carry out digestion within a membrane with which the Lysosomes fuse. Lysosomes can also destroy worn out organelles by fusing with a membrane around the organelles, releasing digestive enzymes and allowing the soluble products to be absorbed back into the cytoplasm. They can also destroy the entire cell when the Lysosome’s membrane will rupture and digest the contents of the cell.


Regina Bailey . (2014). Chromtin. Available: http://biology.about.com/od/geneticsglossary/g/chromatin.htm. Last accessed 01/07/2014.

Regina Bailey . (2014). Endoplasmic Reticulum. Available: http://biology.about.com/od/cellanatomy/ss/endoplasmic-reticulum.htm . Last accessed 01/07/2014.

Biology4kids.com (2014) Cell Structure & Function. Available: http://www.biology4kids.com/files/cell_nucleus.html Last Accessed 03/07/2014.

Monger G. Roberts M. & Reiss M. (2000).Advanced Biology. London: Nelson. 40-50

Tortora & Grabowski. (2003). Principles of Anatomy & Physiology. New York. John Wiley & Sons Inc. 60-100.


Erythrocytes carry oxygen and have unique structures with no nucleus and all other organelles absent. They have a biconcave disc shape, which allows for a large surface to volume ratio for the absorption of oxygen. They are surrounded by a thin flexible plasma membrane and are filled with haemoglobin. The lack of a nucleus and other organelles allow more haemoglobin to be packed into the cell, a single haemoglobin molecule can carry a total of four oxygen molecules.

Ciliated Epithelial Cells line cavities where materials are moved, for example the fallopian tubes. They have cilla on the free surface of the cell, which beat rhythmically to propel material along, for example an egg from the Ovary to the Uterus.

Spermatozoa cells fertilise the ovum. They are shaped into three main regions, the head contains the nucleus and DNA. The middle piece contains tightly packed mitochondria to provide the power for the motion of the tail. The tail is a modified flagella and is used to propel the spermatozoa forwards towards the egg. It is shaped this way to ensure it can propel itself along to reach and fertilise the ovum.

Word Count:190


Education Portal (2014) Ciliated Epithelium: Function Structure and Diagram. Available http://education-portal.com/academy/lesson/ciliated-epithelium-function-structure-diagram.html#lesson Last Accessed 03/07/2014

Monger G. Roberts M. & Reiss M. (2000). Advanced Biology. London: Nelson. 63-64, 218-228, 502-505.

The cell membrane is a fluid mosaic model made up of phospholipids, proteins, carbohydrates and cholesterol. The membrane acts as a selectively permeable barrier and has a bilayer of phospholipids with hydrophilic heads, and hydrophobic tails. The phospholipids naturally align into a bilayer to allow the hydrophobic tails to avoid the extracellular fluid and the cytoplasm, thus forming a circle around each cell. Protein takes the form of globules dotted about in a mosaic pattern along the bilayer, with some penetrating all the way through the pores. These proteins serve as enzymes for chemical reactions and enable substances insoluble in lipid to move across the bilayer. There are short polysaccharide chains attached to the outside of the membrane, most attached to proteins which form glycoproteins. The glycoproteins help in the interaction with other cells and hormones and the recognition of foreign molecules. The cholesterol in the membrane serves to make it the bilayer more stable and prevent it from solidifying if the temperature is low.

Word Count: 165


Dummies.com. (2014).The Fluid-Mosaic Model of the Cell Plasma Membrane.Available: http://www.dummies.com/how-to/content/the-fluidmosaic-model-of-the-cell-plasma-membrane.html. Last accessed 06/07/2014.

Hardman. J. (2014).Lipid Bilayer.Available: http://www.fastbleep.com/biology-notes/31/170/969. Last accessed 06/07/2014.

S-cool.co.uk. (2014).The Cell Membrane.Available: http://www.s-cool.co.uk/a-level/biology/cells-and-organelles/revise-it/the-cell-membrane. Last accessed 06/07/2014.

Monger G. Roberts M. & Reiss M. (2000).Advanced Biology. London: Nelson. 56-59.


Active transport is the movement of molecules or ions against a concentration gradient. It requires energy, which comes from respiration which involves the synthesis of ATP.

Passive Transport is the net movement of molecules or ions from an area of high concentration, to an area of lower concentration. It is a passive process and does not require energy.

Osmosis is the net movement of water molecules through a partially permeable membrane from a region of high concentration to a region of lower concentration.




Active Transport

Use of Energy

Doesn’t require energy and will take place in living and non living systems.

Doesn’t require energy. Water will move from an area of high concentration, to one of low concentration.

Requires energy from respiration. Involves the use of carrier proteins, coupled with ATP which enables them to move molecules against a concentration gradient. Ion gradients created by active transport can then be used to provide energy for the transport of other molecules and ions.

Concentration Gradient

Takes place down the concentration gradient from a region of high concentration, to one of low concentration until equilibrium is reached. Facilitated diffusion will also take place down the concentration gradient, but the diffusing molecule combines with a carrier protein.

Takes place down the concentration gradient until equilibrium is reached. Water molecules can move in both directions across the membrane.

Takes place against the concentration gradient.

Structures that facilitate transport

Cell membrane and a carrier protein is involved in facilitated diffusion.

A selectively permeable membrane.

Uses carrier proteins, coupled with ATP which pump compounds against the concentration gradient.

Molecules transported

Hydrophobic and small uncharged molecules can diffuse through the cell membrane, such as oxygen and carbon dioxide. Large molecules or ions cannot move through the membrane.

Only water molecules are transported via osmosis.

Nutrients and unwanted substances can be transported allowing cells to take in nutrients when the concentration outside is low and vice versa with unwanted substances. For example the sodium-potassium pump in nerve cells which helps nerve impulses.

Word Count : 329


Monger G. Roberts M. & Reiss M. (2000).Advanced Biology. London: Nelson. P.103-114.

Reinhardt. D. (2010).Cell Membranes Structure Osmosis Permeabilty Transport Ideas.Available: http://www.sciencesuperschool.com/Cell-Membranes-Structure-Osmosis-Permeabilty-Transport-Ideas.php. Last accessed 06/07/2014.

S-cool.co.uk. (2014).Movement. Available at http://www.s-cool.co.uk/a-level/biology/cells-and-organelles/revise-it/movement. Last Accessed 06/07/2014.

Tortora & Grabowski (2003).Principles of Anatomy and Physiology. 10th ed. New York: John Wiley & SonsInc. 65-70.

Type of tissue

How the structure of the tissue is linked to the function

Nerve tissue

Sense stimuli and transmits signals. Allows organism to sense stimuli and respond accordingly. It is comprised of neurons which have a cell body containing the nucleus and other organelles, and projections called Dendrites and Axons. Dendrites are tapering, short cell processes covered in branches called dendritic spines, they are the receiving portion of the neuron and increase the surface area of them to help receive impulses Axons are singular, thin and very long processes which are the output portion of the neuron, conducting nerve impulses to other neurons or other tissues.

Muscle tissue

Consists of muscle fibres that use ATP to generate force. Muscle tissue is classified into three types; Skeletal, Cardiac and Smooth. All have muscle fibres, but structure depends on the location and function. Muscle tissue produces body movements, stabilises body position, produces heat and moves substances and regulates organ volume. Cardiac and smooth muscle is striated and it’s movement involuntary; skeletal muscle tissue movement is usually voluntary. It is specifically adapted to have elasticity, and extensibility; for example in the stomach when expanding to accommodate food and to have contractibility and electrical capability to enable it to perform its functions.

Connective tissue

Widely distributed tissue in the body with a variety of functions depending on location. It binds together, supports and strengthens other tissues, protects and insulates organs, is the transport system of the body and is the storage site of energy reserves and site of immune responses. Consists of cells and extracellular matrix which fills the wide space between the cells. Variations in the composition of the extracellular matrix determines the properties of the connective tissue, for example if it is calcified it can form bone, or teeth. Dense regular connective tissue has loosely packed collagen fibres which are arranged in parallel, and found in ligaments and tendons. This arrangement means they allow some stretch but are resistant to loaded tension forces.

Epithelial tissue

Consists of closely packed continuous sheets of cells, in one or more layers with little intercellular space between them. Lines all major cavities of the body and most organs. There are six types of epithelial tissue but all are separated from the underlying tissue by a basement membrane, which provides structural support and binds it to the neighbouring structures. Depending on the location, the functions of epithelial tissue can include protection, diffusion, excretion and absorption, transportation and movement. Ciliated epithelial cells are columnar and contain goblet cells, they line the upper respiratory tract and move mucus and other substances by ciliary action.

Word Count: 436


Bailey. R. (2014). Nervous Tissue. Available: http://biology.about.com/od/anatomy/a/aa031408a.htm. Last accessed 06/07/2014.

Davidson College. (2010). Epithelial Cells. Available: http://www.bio.davidson.edu/people/kabernd/berndcv/lab/epithelialinfoweb/index.html. Last accessed 06/07/2014.

The University of Leeds. (2014). Connective Tissue. Available: http://histology.leeds.ac.uk/tissue_types/connective/connective_cells.php. Last accessed 06/07/2014.

Tortora & Grabowski (2003). Principles of Anatomy and Physiology. 10th ed. New York: John Wiley & Sons Inc. P.110-120, 117, 132-138 and 274-303.


The heart is an organ in the cardiovascular system which acts as the body’s circulatory pump. It is made of cardiac muscle tissue in three layers, as shown below. (Georgia Highlands College, 2014)

The endocardium is the innermost layer of epithelial tissue which is in contact with the blood flowing in and out of the heart. The myocardium is made up of myocytes which contract involuntarily to make the heart pump. The pericardium/ epicardium is the outer double layered sac, made of connective tissue which protects the heart and roots of the veins and arteries extending from it.

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The lungs are covered in a thin tissue called the pleura and are made up of bronchioles, which end in clusters of alveoli. They are an organ in the respiratory system and their function is to bring oxygen in and remove carbon dioxide from the body. This gas exchange takes place in the alveoli which line the inner surface of the lung, as shown below.

COPD Lung disease - diagram

(Breathmatters.org. 2014)

The alveoli are specialised for efficient gas exchange because they have a large surface area, are very thin and are fluid lined which enables gas to dissolve.

The heart and lungs interact to supply the rest of the body with oxygen, and to remove carbon dioxide. The heart pumps deoxygenated blood in the pulmonary circuit from the heart via the pulmonary artery, to the lungs to become oxygenated; then back to the heart via the pulmonary vein. The heart then pumps this blood via the systemic circuit from through the aorta into the arteries and capillaries and out to the rest of the body. Deoxygenated blood then returns to the heart via the venae cavae to re-enter the pulmonary circuit.

Word Count: 260

Diagram One


(Georgia Highlands College, 2014)

Diagram Two

COPD Lung disease - diagram

(Breathmatters.org. 2014)


Breathmatters.org.(2014) Diagram of Human Lung. Available at http://www.breathmatters.org/what-is-copd-lung-disease.php. Last accessed 14/07/2014.

Georgia Highlands College (2014) A Section of the Heart, showing its three layers: epicardium, myocardium and endocardium. Available at http://www.highlands.edu/academics/divisions/scipe/biology/faculty/harnden/2122/images/heartlayers.jpg. Last Accessed 14/07/2014.


American Thoracic Society (2014). Anatomy and function of the normal lung. Available http://www.thoracic.org/clinical/copd-guidelines/for-patients/anatomy-and-function-of-the-normal-lung.php. Last accessed 13/07/2014.

Bailey,R. (2014) The Lungs. Available http://biology.about.com/od/anatomy/ss/the-lungs.htm. Last Accessed 13/07/014.

Curoservice.com (2014). Lungs and Circulation. Available http://www.curoservice.com/parents_visitors/lungs_circulation/structure_alveoli.asp. Last Accessed 13/07/2014.

Lewis. T (2013). Human Heart, Anatomy, Function & Facts. Available http://www.livescience.com/34655-human-heart.html. Last accessed 13/07/2014.

Tortora & Grabowski (2003). Principles of Anatomy and Physiology. 10th ed. New York: John Wiley & Sons Inc. P.696-703 & 859-861.


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