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Cardiovascular, Respiratory and Gastro-intestinal Systems

Paper Type: Free Essay Subject: Biology
Wordcount: 3468 words Published: 29th May 2018

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Part 1 – Explain the anatomy of the cardiovascular system and the role played by each of the major parts. (400 words)

The heart is a muscular organ that pumps blood. Right/left sides are divided into two chambers.

The right side includes the pulmonary artery, vena cava, right atrium, tricuspid valve, septum and right ventricle. Blood is pumped through the pulmonary circuit (circuit between heart and lungs). The right ventricle receives deoxygenated blood from the right atrium and pumps this into the lungs. Gaseous exchange occurs and oxygenated blood is taken back to the heart.

The thicker left side of the heart consists of the aorta, pulmonary vein, left atrium, bicuspid valve and left ventricle. Blood is pumped through the systemic circuit (circuit between the heart and other organs). This circuit transports oxygen/nutrients via blood to body tissues, and carries deoxygenated blood containing waste materials away.

This double circulation system helps maintain pressure levels as systemic system pressure may damage sensitive tissues in the respiratory system, while low pressure in the pulmonary system wouldn’t be enough to transport blood around the body.


Red blood cells contain haemoglobin – a red pigment that can bind oxygen and transport it. The cells’ biconcave shape, and lack of nucleus, gives them a large surface area to take up more oxygen. They’re small/flexible which enables travel through capillaries. They transport oxygen from lungs to the rest of the body.

White blood cells – an essential part of our immune system – are responsible for producing antibodies and destroying harmful microorganisms.

Platelets stop bleeding by clinging to damaged vessels forming a plug. Chemicals are released sealing the vessel, stopping blood loss and ensuring infections can’t reach exposed blood/pathogens are kept out.

Plasma – the fluid part of the blood – is a mixture of water, proteins and dissolved substances. It carries carbon dioxide and waste away from cells along with proteins, enzymes and digestion products.

Blood vessels

Arteries have thick walls and a middle layer composed of elastic muscle fibres. They take oxygenated blood away from the heart to where needed and can increase in size to accommodate increased blood flow. They push blood through the body/maintain the pressure wave exerted by the heart.

Veins bring deoxygenated blood to the heart. They have thin walls, few elastic fibres and contain blood pumped under low pressure. Their valves push against the vein when blood moves to the heart and form cusps to block the vein and keep blood in place, making sure blood under low pressure doesn’t move backwards.

Capillaries take nutrients/oxygen to cells. They link arteries to veins and are tiny/delicate. Thin walls allow gaseous exchange from cellular fluid to blood and vice versa. There’s a large number of capillaries through tissues of the lungs and body.

439 words

TAQ 1 – Part 2

Explain the structure of the respiratory system by completing a table similar to the one below. (300 words)

Respiratory system component



Upper tract


Includes accessory organs aiding food digestion (tongue, teeth, salivary glands).

Can supplement/replace nasal cavity functions. Breathing through mouth gives shorter distance/large diameter for air to quickly enter body.

Nose / Nasal Cavity

Made from cartilage, bone, muscle and skin.

Hollow space between nose and skull lined with hairs/mucous membrane.

Supports/protects anterior portion of the nasal cavity.

Nostril hair filters air. Mucous traps dust, particles and bacteria to prevent them entering bronchial system. Cilia pass mucous backwards to be swallowed. Air is warmed/moistened here preventing air damaging lung tissue.


Muscular funnel connecting mouth and nose to larynx and oesophagus.

Transports food/water to oesophagus and air to larynx. Cilia lining/mucous removes air impurities.


Composed of cartilage connected by ligaments/muscles. Top flap called epiglottis.

Epiglottis prevents food/fluid entering the larynx (and lungs). During breathing its open. When swallowing it seals with the larynx, re-routing foods/fluids to oesophagus.

Lower tract


Tube lined with cilia. Supported by c-shaped cartilage rings providing support/stop collapse. Very flexible.

Provides clear airway for air to enter/exit lungs. Works with larynx. Cilia/mucous move unwanted particles away.


Two. One goes to left lung, one to right.

Forms the system which disperses air into lungs. Cilia /mucous move unwanted particles away.


Smaller tubes branching out from bronchi. Less cartilage/more smooth muscle.

Control regulation of air in/out of lungs. Constrict when less air is needed/expand when more needed e.g. during exercise. Cilia/mucous move unwanted particles away.


Small sacs found in each lung. 300million in each. Surrounded by capillaries (separated from alveoli by thin membrane).

Gaseous exchange occurs here. Oxygen diffuses from air into lungs and carbon dioxide diffuses from the bloodstream into air.


Spongy organs inside thoracic cavity, surrounded by ribs and diaphragm (underneath). Right lung has 3 lobes, left has 2. Surrounded by pleural membrane that provides the lung with space to expand.

Responsible for inspiration and expiration due to movement of thoracic cavity. Provides a large surface area for gas exchange.


328 words

TAQ 1: Part 3

Explain the structure of the gastro intestinal system, using a table similar to the one shown below. (300 words)

Digestive system organ




Includes accessory organs aiding food digestion (tongue, teeth and salivary glands).

Where food enters/digestion begins. Breaks down food mechanically/chemically. Food is tasted and bolus moved to back of mouth and swallowed. Produce saliva (water and solutes). Enzyme ‘salivary amylase’ initiates starch breakdown.


Muscular tube running behind trachea. Two sphincters ensure food travels one way at top & bottom.

Food propelled downwards using wave like contractions/relaxations (Peristalsis).


Walls have ridges/folds (rugae) which allow expansion during digestion.

Connects oesophagus to duodenum. Stored up to 4 litres of food until it’s moved into small intestine. Mechanical/chemical digestion site. Muscle walls aid bolus breakdown. Parietal cells secrete hydrochloric acid which kills microbes. Chief cells secrete pepsinogen which, when in contact with hydrochloric acid, activates (becomes pepsin) breaking down proteins. When both processes have occurred, chyme is left.

Small Intestine

3m long. Large surface area for absorption. Folded into small space in abdominal cavity. Villi further increase surface area. Microvilli increase area even more.

Duodenum – Most digestion occurs here. Immediately follows stomach. Enzymes break down complex carbohydrates s/proteins/fats for ease of absorption.

Jejunum – Most absorption occurs here. Food assimilated by body. Amino acids absorbed by villi via active transport. Monosaccharide’s absorbed by active transport/facilitated diffusion. Fatty acids diffuse into blood capillary.

Ileum – Absorbs vitamin B12 and reabsorb bile salts.


Located behind stomach. 6 inches long, shaped like a flat pear. Head sits near duodenum.

Endocrine – releases hormones (glucagon and insulin) to stabilise blood glucose. Exocrine – releases salts and enzymes (amylase and lipase) as pancreatic juice to neutralise hydrochloric acid from stomach and aid digestion.

Large intestine (colon)

1.5m long. 3 times as wide as small intestine. Different parts.

Absorption of water and inorganic ions (sodium, potassium). Fermentation of remaining carbohydrates. Hydrogen, carbon dioxide and methane released here.


8 inch chamber connecting colon to anus

Storage of faeces ready for release to anus.


2 inch long canal. Consists of pelvic floor muscles/2 anal sphincters.

Where faeces are expelled.

328 Words


Write a short account explaining how oxygen gets from the environment to the cells and vice versa. (400 words)

Inhalation and exhalation is the way humans take in oxygen to feed cells/tissues and release waste products.

Oxygen taken into our lungs diffuses from alveoli through tiny, thin capillaries to red blood cells (RBC). 95% of oxygen is carried via RBC haemoglobin. Haemoglobin molecules consist of 4 oxygen binding sites. Once oxygen attaches to a site, it’s easier for additional molecules to bind due to the RBC’s changing shape/size. Haemoglobin and Oxygen form Oxyhaemoglobin. Once saturated the RBC travels to where needed.

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Once at the cell, and due to the low parietal pressure (concentration) of oxygen molecules, diffusion occurs. Parietal CO2 (PCO2) at the cell is high due to cellular respiration waste so, as oxygen disassociates, CO2 binds. The process of CO2 competing with oxygen for binding sites causes even more oxygen to disassociate. CO2 also combines with water creating carbonic acid (due to the presence of the enzyme Carbonic Anhydrase). A proton from this acid binds to Haemoglobin and causes more oxygen disassociation, freeing up more space for CO2 transportation. CO2 + haemoglobin creates carbaminohaemoglobin. It’s transported by RBC back to the lungs where – due to concentration of CO2 being low – the waste product diffuses into alveolar air space for removal via exhalation.

The process of getting oxygen from the air into the blood and removing carbon dioxide is called gaseous exchange. Lung alveoli are adapted to make gas exchange happen quickly and efficiently.

Alveoli characteristics that allow gas exchange are:

  1. Made up of sacs due to extensive folding of the membrane surrounding them. Gives lungs a large surface area, meaning gas exchange can take place quickly.
  2. Have moist thin walls (one cell thick)
  3. Have lots of tiny blood vessels (capillaries). RBCs flowing through them are flexible/able to squeeze through by pressing against capillary walls. This reduces the distance O2 has to travel/speeds up gas transfer.

O2/ CO2 move from alveolar air to blood/blood to alveolar air by diffusion which occurs because of the difference in the volume of oxygen and carbon dioxide in the air (alveoli) and in the blood (capillaries). During inhalation there is a higher concentration of oxygen in the alveoli than in the blood. Oxygen diffuses through the alveoli’s thin walls and into RBC where it binds haemoglobin and is transported away for use.

While this is happening, the carbon dioxide produced as waste from cellular respiration is exported from cells into the bloodstream, making the concentration of carbon dioxide higher in the blood than within the air in the alveoli. Therefore, when carbon dioxide arrives at the lungs, it diffuses through the thin membrane into the alveoli and expelled during exhalation.

439 words


Using examples give a short account of the role of enzymes within the process of digestion. (300 words)

Digestion is the breakdown of carbohydrates, proteins and fats into small soluble substances that can be absorbed into blood. Once they are broken down they can be used as energy sources/building materials for cell maintenance, growth and repair.

Enzymes are important in digestion. They speed up biological reactions and are created by specialised cells and released for us in digestion where they pass into the digestive system to catalyze food molecule breakdown.

There are three different kinds of digestive enzyme, each working on a different food group.

  1. Carbohydrase – Catalyses starch found in sugar, potatoes, pasta and rice. Amalyse breaks starch down into simple sugars (glucose). The enzyme is produced in the salivary glands, pancreas and small intestine.
  2. Protease – Catalyses proteins found in food such as fish and chicken into amino acids. The enzyme is produced in the stomach, pancreas and small intestine.
  3. Lipase – Catalyses lipids (fats and oils) found in butter, crisps and cheese into fatty acids and glycerol. It’s produced in the pancreas and small intestine.

When food is chewed, the salivary glands produce the enzyme ptyalin which consists of amylolytic enzymes that help to break down starches in the food; this enzyme continues to work as food passes down the oesophagus.

When it reaches the stomach, food can remain there for up to an hour. Salivary amylase can digest as much as 30-40% of starches present. The stomach continues mechanical digestion by churning the bolus to create chyme. Gastric lipase, gelatinase and pepsinogen (inactive form of pepsin) are amongst those enzymes secreted. Pepsin is activated via acid hydrolysis with the hydrochloric acid secreted by the stomach. This is the time the stomach begins the enzymatic digestion of proteins and some fats, creating peptides, fatty acids and glycerol essential for cell maintenance, repair and replication.

The food then leaves the stomach and enters the small intestine. Here a few enzymes, e.g. maltase which produces glucose, are produced to complete the digestion of food.

327 words


This unit discusses the systems that supply the cell with everything that it needs. How the three systems discussed function in supporting the cell?

Part 1: Cardiovascular system (100 words)

The cardiovascular system supports the cell by sending, via the systemic system, products the cell needs such as oxygen (haemoglobin in red blood cells), antibodies (white blood cells), platelets (to stop damaged vessels leaking) and glucose (cellular energy). The heart pumps and products are sent via arteries that bring blood to capillaries which are very close to the cell. Diffusion then occurs. The system also takes deoxygenated blood (CO2, proteins, digestion waste products) via red blood cells and plasma carried in veins back to the lungs for gas exchange and removal.

91 Words

Part 2: Respiratory system (100 words)

The respiratory system using inhalation and expiration to take up and expel products that cells need/don’t need – such as oxygen and CO2. Without key respiratory system organs oxygen wouldn’t be able to be taken from air, to blood, to cells. This would cause cell death. Cells produce CO2 as a process of cellular respiration and a build up of this in the body would be toxic. If the blood took this away, but did nothing with it, we would die. Gas exchange in the alveoli keeps CO2 levels safe and allows cells to function and dispose of cellular waste products efficiently.

101 Words

Part 3: Gastrointestinal system (100 words)

Cells need to repair, maintain and replicate as and when needed. To do this, they need specific products such as amino acids, fatty acids, glycerol, glucose etc. Without the breakdown of carbohydrates, proteins and fats, our cells would not receive these products. The gastrointestinal system supports the cell by producing specific enzymes that convert large food particles, e.g. proteins, to smaller soluble particles that can be sent via blood and used by the cell for cellular respiration and to create RNA, DNA, ATP etc. All are important elements for cell survival.

91 Words


Bbc.co.uk, (2015). BBC – GCSE Biology – Digestive system – Revision 2. [online] Available at: http://www.bbc.co.uk/education/guides/zwqycdm/revision/2 [Accessed 2 Mar. 2015].

Bbc.co.uk, (2015). BBC – KS3 Bitesize Science – Life processes : Revision, Page 6. [online] Available at: http://www.bbc.co.uk/bitesize/ks3/science/organisms_behaviour_health/life_processes/revision/6/ [Accessed 2 Mar. 2015].

Cleveland Clinic, (2015). The Structure and Function of the Digestive System. [online] Available at: http://my.clevelandclinic.org/health/ns_overview/hic-the-structure-and-function-of-the-digestive-system [Accessed 2 Mar. 2015].

InnerBody, (2015). Respiratory System. [online] Available at: http://www.innerbody.com/anatomy/respiratory [Accessed 2 Mar. 2015].

InnerBody, (2015). Respiratory System. [online] Available at: http://www.innerbody.com/anatomy/respiratory [Accessed 2 Mar. 2015].

Khan Academy, (2015). Mouth. [online] Available at: https://www.khanacademy.org/test-prep/NCLEX-RN/rn-gastrointestinal-system/rn-the-gastrointestinal-system/v/mouth [Accessed 2 Mar. 2015].

Mcb.berkeley.edu, (2015). THE DIGESTIVE SYSTEM. [online] Available at: https://mcb.berkeley.edu/courses/mcb32/Miller notes- digestive system [Accessed 2 Mar. 2015].

Roberts, M. (1974). Biology, a functional approach. London: Nelson, pp.121 – 162, 232.

Tortora, G. and Grabowski, S. (2003). Principles of anatomy and physiology. New York: Wiley, pp.127 – 154, 161, 162.


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