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Structure of the Cardiovascular and Respiratory Systems

Paper Type: Free Essay Subject: Biology
Wordcount: 3770 words Published: 14th May 2018

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Cardiovascular system component


Function (s)


Figure 1: Internal view of the heart


Atrioventricular valves (mitral and tricuspid valves) – separate ventricles from atria

Aortic valve – divide left ventricle + aorta

Pulmonary valve – separates right ventricle + pulmonary artery

One directional blood flow:


stop back-flow into atria

-Aortic valve:

opens = blood enters aorta

shuts = stop blood returning to heart


opens with cardiac cycle contraction




Right/left atrium (atria) – thin walled

Right and left ventricles – thick muscular chambers pump blood out of the heart


-Blood from veins. Deoxygenated blood from body on RHS (systemic veins), oxygenated blood from lungs on LHS (pulmonary veins). Push blood into lower chambers (ventricles) – short distance, minimal muscle.


-Wall of left ventricle denser than right to pump blood all around body. Right ventricle muscle thinner, only pumping to lungs.

Figure 2 : The heart wall



-Lining of valves/chambers -Connective + epithelial tissue

Purkinje fibres regulate contractions relaying cardiac impulses = ventricles to contract

Myocardium : -Cardiac muscle (unique to heart) uninucleated, striated


-Muscle cells contain myofibrils

-Pumps blood, does not tire

-Striated muscle suited to short contractions


-Fibrous, surrounds heart -Inner layer (serous pericardium) + visceral layer (on inside) = forms a friction reducing layer

-Protects heart from infection/external movement

-Stops heart from over expanding when blood volume increases


Figure 3: The composition of blood


-Liquid in which components suspended

-Contains gamma globulin + fibrinogen

White blood cells (or leukocytes):

-Part of immune system

Red blood cells (erythrocytes):

-Made in bone marrow, contain haemoglobin


-Fragments of bone marrow cells (megakaryocytes)

-No nucleus


-Oxygen around body from lungs

-Carbon dioxide  lungs for expulsion

-Nutrients from gastro-intestinal system  body cells

– Hormones from endocrine glands  body cells


-Removes carbon dioxide/ waste from cells

-White blood cells destroy harmful organisms/create antibodies

-Platelets form clots , gathering together/stopping bleeding


-pH via blood buffers

-Body temperature – water in plasma extracted through blood and via skin

Blood vessels

Figure 4: Comparison of blood vessels


-Muscular tubes – expand/contract

-Lined by smooth tissue:

-Intima, endothelium lining

-Media, muscle layer

-Adventitia, connective tissue,

links arteries/tissues

Figure 5: Artery composition

-Distensibility of artery means lumen can increase with pressure, accommodating different levels of blood flow



-Outer wall = connective tissue,(tunica adventitia/tunica external)

-Middle layer = smooth muscle (tunica media)

-Central layer = endothelial cells (tunica intima)

Figure 6: Cross-section of a vein

– Return deoxygenated blood to heart

– Thin walls as low pressure

-Form edges stopping back-flow



-Small blood vessels in body tissues

-Carry blood from arteries to veins

-Single layer of endothelial cells + basement membrane

-Exchange nutrients/waste products between blood and tissue cells via interstitial fluid

-Single layered cell allowing easy passage

Word count = 439

Part 2 – Explain the structure of the respiratory system by completing a table detailing component, structure and function(s). (300 words)

Respiratory system component


Function (s)

Upper respiratory tract

Figure 7: Upper respiratory tract

Mouth – Alimentary canal entrance, epithelium membrane

-Supplements nasal airflow

-Quicker route to nasal cavity

Nose – Bone, muscle, skin and cartilage. Cilia line nostrils.

-Main respiratory system entrance

-Air cleaned/filtered by cilia

Nasal cavity – Divided by nasal septum made of cartilage/bone – mucosa lining. Cilia cover cells (mucociliary elevator).

-Cilia trap dust /bacteria


Pharynx – Skeletal muscle – mucus membrane lining. Connects mouth/nose to larynx/oesophagus. Contains cilia.

-Directs food/water to oesophagus, air to larynx

-Filters dust/bacteria


Larynx – Cartilage connected by muscles/ligaments. Tissue flap called epiglottis.

-Epiglottis opens to let air in

-When swallowing larynx/epiglottis close so food/fluid can enter oesophagus

-Coughing reflex in larynx prevents choking

Lower respiratory tract

Trachea – Muscle/connective tissue rings of cartilage. Lumen lined with mucosa and cilia.

-Rings = support

-Flexibility allows closing as food enters stomach

-Allows air exchange

-Foreign substances trapped by mucosa

Bronchi – Two-way split at bottom of trachea. Made of smooth muscle, mucosa, cartilage.

-Cartilage stops collapse during inhalation/exhalation and tissue damage

-Mucus prevents bacteria entering lungs

– Smooth muscle is involuntary, governed by airflow requirements

Bronchioles – Branches from bronchi made of smooth muscle; lobular, terminal and respiratory bronchioles

-Carry air from trachea to lungs

-Smooth muscle walls regulate airflow


Alveoli – Thin walls, large surface area, fluid lined, encapsulated by capillaries. Squamous epithelial tissue.

-Gas exchange of oxygen and carbon dioxide happens here simultaneously, fluid lining helping them dissolve

-Oxygen moves easily through walls/capillaries into red blood cells



Figure 8: Bronchi, bronchial tree and lungs

Spongy air filled organs in chest. Contain bronchi, bronchioles, alveoli. Lined with epithelial cells and cilia. Covered by pleura, as is the chest cavity and attached via surface tension. Divided by fissures – right lung has 3 lobes, the left 2. Smooth muscle at bottom.

-Provide oxygen to capillaries for blood oxygenation

-Remove carbon dioxide

-Pleura secrete fluid = lubricant between lungs/chest cavity upon movement

-Smooth muscle contracts

-Cells and cilia trap bacteria to prevent lung infection

Word count = 330

Part 3 – Explain the structure of the gastro-intestinal system by completing a table detailing component system organ, structure and function(s). (300 words)

Digestive system organ


Function (s)


Figure 9: Bolus moving down oesophagus

Fibrous, muscular tube running from pharynx to stomach. Secretes mucus.

Upper oesophageal sphincter at entrance to oesophagus. Cricopharyngeus muscle attached to cricoid cartilage. Peristalsis during swallowing (contractions) controlled by medulla oblongata.

-Transports food to stomach

-Sphincter regulates food coming from laryngopharynx

-Elevation of larynx during swallowing makes sphincter relax/bolus enter

-Peristalsis drives bolus to stomach

-Mucus from oesophagus glands lubricate food/reduce friction



Figure 10: The stomach

Stomach walls = smooth muscle layers (longitudinal, circular and oblique muscle), submucosa and mucosa (deep). Inner layer has gastric folds or rugae.

Stomach divided; fundus/ body/antrum.

-Secretes acid/enzymes to breakdown food further

– Rugae expand and move food during digestion

-Mucus cells protect stomach from its own secretions

-Blood supply of submucose provide nutrients to stomach wall

-Smooth muscle layers contract to mix/move food along digestive tract

Small intestine

Figure 11: The small intestine

Made up of duodenum, jejunum, ileum. Lumen diameter smaller than inlarge intestine. Wall embedded with enzymes. Large surface area comprising villi and microvilli. Villi cells have blood capillaries running through them and thin membrane.

-Nutrients absorbed from the food using enzymes released by pancreas (eg:amylase) and bile from liver

-Contracts and pushes food into large intestine

-Thin membrane means material can be absorbed into bloodstream quickly

-Bicarbonate in duodenum neutralises stomach acid

– Amino acids absorbed by villi via active transport

-Short chain fatty acids diffuse into blood capillary

Large intestine (colon)

Figure 12: The large intestine

Made up of cecum, appendix, colon, rectum, anal canal, anus.

Folded lining and on lumen side of the gut wall there is a mucosa layer lined with many goblet cells which produce mucus. In the anal canal, the epithelial layer stratified squamous tissue and internal and external anal sphincters.

-Absorption of water and inorganic ions (sodium/potassium) return to body

-Extracts water from food residues

-Converts leftover material to faeces

-Collects ions from bloodstream to be excreted

-Mucus needed to lubricate pellets for excretion

-Stratified squamous tissue to resist abrasion

-Sphincters keep anus closed until excretion required

Word count = 327


Assessment Criteria 1.2 and 2.2

Criteria 1.2 Explain the mechanism of transport of oxygen and carbon dioxide in the body

Criteria 2.2 Explain the principle of gaseous exchange in the lungs

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

Oxygen from the environment gets into the body by breathing and this supplies all the parts of the body. We breathe in oxygen and exhale carbon dioxide via the mouth, nose, trachea, lungs and diaphragm.

Oxygen enters the respiratory system at the mouth and nose and passes through the larynx and trachea. The trachea branches into two tubes called bronchi which split again to form the bronchial tubes. The inhaled oxygen travels down these tubesinto the lungs and intolittle spongy air sacs called alveoli.

In the alveoli oxygen diffuses through the respiratory membrane into the bloodin the lung capillaries. Diffusion will happen here as long as the concentration of oxygen is greater than it is in the blood as particles diffuse down a concentration gradient from where there is a high concentration to low. The rate of this process is regulated by the amount of carbon dioxide and oxygen in the blood and happens quickly through the air/blood barrier in the lungs. This barrier is comprised of alveolar epithelium, basement membrane, and endothelium. Its purpose is to make sure that air does not get in the blood and form bubbles and blood get into the alveoli.

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The layers of the cells lining the alveoli and these capillaries are only one cell thick and are close to one another, making it easy for the oxygen to enter the red blood cells to bind to the haemoglobin molecule. It is then transported from areas of high concentration (in the lungs) to areas of lower concentration (in the capillaries). When the red blood cells enter tissue capillaries the oxygen detaches from the haemoglobin, moving out of the red blood cell and capillary into the interstitial space where it diffuses into the cells to be carried around the body.

Blood in the veins has lots of waste in it and gas exchange occurs between the alveolar air and the blood. Carbon dioxide in the red blood cells is transported as dissolved carbon dioxide, mixed with haemoglobin, or as bicarbonate and arrives at the capillaries for transfer into the alveoli. It is has a high carbon dioxide and low oxygen content, the opposite of blood arriving. As a result an exchange happens. The oxygen sticks to the haemoglobin, diffusing into the blood and carbon dioxide diffuses to the alveoli. The diaphragm, a piece of muscle which lines the lungs, contracts to draw oxygen into the lungs and as it relaxes carbon dioxide is forced out. When leaving the body carbon dioxide follows the same structural route the oxygen did upon entry.

Word count = 429


Assessment Criteria 1.2 and 2.2

Criteria 3.2Summarise the role of enzymes in the digestive process

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

An enzyme is a recycled protein molecule which catalyses a specific reaction. Food and drink comprise large molecules and these need to be hydrolysed (in this case made smaller) so they can be absorbed/assimilated. Enzymes are used within the digestive system to provide cells with the fuel from the macromolecules (large molecules) of carbohydrates, proteins and fats they need to function properly. These are broken down in small units of amino acids, sugars and fatty acids which can penetrate the villi lining the intestine.

Figure 13: Diagram to show how the enzymes allow the substrate (the substance on which enzymes attach) to attach to the active site (where the molecules fit)

Digestive enzymes are produced in saliva in the salivary glands, the cells of the stomach lining, the pancreas in pancreatic juice and in the small intestine.

Salivary amylase in the mouth initiates the breakdown of starch, a type of carbohydrate. This must be broken down into monosaccharide as starch is a polysaccharide which the body cannot digest. This is called maltose and is eventually digested to glucose in the duodenum.

In the stomach lining gastric juice is secreted and contains the enzyme protease (pepsin). The enzymes digest protein macromolecules breaking them down into amino acids. They are assisted by hydrochloric acid which alters the pH to a pH which protease works best at.

Acinar cells in the pancreas produce the enzymes and a clear liquid called pancreatic juice which the enzymes need to be in to work. Pancreatic enzymes are: protein digesting proteases (e.g. chymotrypsin/ trypsin – broken down into amino acids); pancreatic amylase which digests carbohydrates (turns starches to sugars) and lipase (turns lipids to fatty acids and glycerol) which digests fats. The enzymes are secreted into the small intestine where they work with brush border enzymes:




Peptides into amino acids


Hydrolyses maltose to glucose


Hydrolyses sucrose to glucose and fructose


Hydrolyses lactose to glucose and galactose

The digestive system does not absorb food, it absorbs nutrients and enzymes facilitate this breakdown.

Word count = 312

TAQ 4:

Assessment Criteria 3.3

Criteria 3.3Explain how the digestive, cardiovascular and respiratory systems are

essential in providing the requirements for cell functioning

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

Part 1 – Cardiovascular system (100 words)

In order that normal cell function be achieved the cardiovascular system:

  • pumps oxygenated blood out of the heart via the aorta, transporting oxygen to every cell in the body undergoing respiration (process by which chemical energy of food molecules is captured and converted to ATP)
  • transports nutrients (eg amino acids, sugars and fatty acids) to cells from the digestive system
  • transports hormones from glands to target organs where they bring about change
  • regulates the water content of cells – this is vital as it ensures the sufficient and efficient movement of electrolytes, nutrients and gases through the cells.

Word count = 101

Part 2 – Respiratory system (100 words)

The respiratory system delivers oxygen and removes carbon dioxide waste from body’s cells via cell membranes in the lungs (external respiration) and in body tissues (internal respiration). Oxygen is essential in cellular respiration which produces energy in cells.

  1. Breathe in  oxygen diffuses from alveoli into blood capillaries.
  2. Oxygen combines with haemoglobin in red blood cells forming oxyhaemoglobin.
  3. Oxygen rich blood leaves lungs.
  4. Gets to cells with low concentration of oxygen, high concentration of carbon dioxide  oxyhaemoglobin dissociates, releasing oxygen.
  5. Internal respiration happens within cell mitochondria.
  6. Carbon dioxide diffuses into blood plasma from cells  removed by diffusing from blood plasma into alveoli.

Word count = 110

Part 3 – Gastrointestinal system (100 words)

The gastrointestinal system breaks down large insoluble molecules like proteins, carbohydrates, and fats into smaller soluble molecules like amino acids, sugars and fatty acids. These small soluble molecules can then pass across the small intestine walls and dissolve in the blood stream. Absorbed through the villi of the small intestine into the blood they can then be carried around the body to cells. The sugar molecules are used by the cells as a source of energy via cellular respiration. Whilst the amino acids and vitamins are used as a building block for other molecules.


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