Biology B5


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Bones and Cartilage


  • The job of a skeleton is to support the body and allow it to move- as well as protect vital organs
  • Fish, amphibians, reptiles, birds and mammals are all vertebrates- they all have a backbone and a internal skeleton. Other animals like insects have their skeleton on the outside
  • An internal skeleton has certain advantages, it can easily grow with the body, its easy to attach muscles to it, its more flexible than an external skeleton.

Bones are living tissues:

Bones are made up of living cells- so they grow, and can repair themselves if they get damaged. Long bones are actually hollow this makes them lighter than solid bones of the same size. The hole in the middle of some long bones is filled with bone marrow. Bone marrow is a spongy sunstances that makes new blood cells- meaning your bones are actually a kind of blood factory.

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  • Bones start off as cartilage in womb. 
  • As you grow, cartilage is replaced by bone. Blood vessels deposit calcium and phosphorus in the cartilage- which eventually turns it into bone. This process is called ossification.
  • You can tell if someone is still growing by looking at how much cartilage is present- if there's a lot then they're still growing.
  • Even when a person has stopped growing the ends of their bones are still covered in cartilage to prevent the bones from rubbing together at joints.

Bones and Cartilage Can Get Damaged:

  • cartilage and bones are both made up of living tissue and so can get infected.
  • Even though bones are really strong, they can be fractured by a sharp knock. Elderly people are more prone to breaking bones as they often suffer from osteoporosis- a condition where calcium is lost from the bones.
  • A broken bone can easily injure nearby tissue- so you shouldn't move anyone who might have a fracture. That's especially true for someone with a suspected spinal fracture- moving them could damage their spinal cord. Damage to the spinal cord can cause paralysis. 
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Joints and Muscles

Joints allow muscles to move:

  • the bones at a joint are held together by ligaments. Ligaments have tensile strength but are pretty elastic.
  • covered in cartilage to stop the bones rubbing together. And because cartilage can be slightly compressed, it can act as a shock absorber.
  • Membranes at joints release oily synovial fluid to lubricate the joints, allowing them to move more easily.

Muscles Pull on Bones to Move Them:

1) Bones are attached to muscles by tendons.

2) muscles move bones at a joint by contracting. They can only pull on bones to move a joint- not push.

3)This is why muscles usually come in pairs, when one contracts the other relaxes.

If joints become damaged or diseased then they can be replaced with artificial joints.

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The Circulatory System

Humans Have a Double Circulatory System:

  • like any circulatory system the heart acts a pump.The hear contracts pushing blood round the body.
  • as blood travels round the body through blood vessels it loses pressure so arteries have the highest pressure, veins have the lowest and capillaries are in between.
  • Lots of animals have a single circulatory system. for this you need a two chambered heart.
  • Humans have a double circulatory system. like two single circulatory systems stuck together.

The Cardiac Cycle

  • blood flows into the two atria
  • the atria contract, pushing the blood into the ventricles
  • the ventricles contract, forcing the blood into the aorta and the pulmonary artery.

We haven't always known this much about the heart:

  • Galen believed that blood was made in the liver and used up in the organs
  • Harvey showed what the valves do in the heart proving it is a pump.
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The Heart

The Heart Rate Changed According to Activity

  • When you exercise, your muscles need more oxygen to work harder so you don't need to breathe faster. Your heart also pumps faster to deliver more oxygenated blood to your muscles.
  • Hormones can also affect your heart rate, e.g. adrenaline is released when you get a shock or you're in danger it increased heart rate to make sure the muscles have plenty of oxygen.

The Heart Has a Pacemaker

  • The heart is told how fast to beat by the pacemaker cells.
  • These cells produce a small electric current which spreads to surrounding muscles causing them to contract There are two clusters of these cells in the heart the sino- atrial node (SAN) and the atrio-ventricular node (AVN).
  • in one complete heartbeat the the SAN produces an electric current first, which spreads to the atria making them contract. The current stimulates the AVN to produce an electric current, this process ensures that the atria contracts before the ventricles.

Echocardiograms Measure the Heart

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Heart Disease

There are three main ways your heart can go wrong:

1) Hole in the heart- a whole in the heart is usually something you're born with. Its a gap in the wall separating either the two ventricles or the two atria, causing oxygen rich blood to mix with deoxygenated blood and leading back to the lungs proving to be very inefficient.

2) Valve Damage- the valves in the heart can be damaged by heart attacks, infection or old age. The damage may cause the valve not to open properly, causing high blood pressure. It may even allow blood to flow in both directions rather than just forward.

3) Coronary Heart Disease- CHD is when the arteries that supply blood to the muscle of the heart get blocked by fatty deposits. This is often results in a heart attack. It can be treated by a coronary bypass operation.when another blood vessel is added to bypass the blockage. 

Lifestyles affect the heart- Unhealthy Diet, Drinking alcohol, smoking, stress and drugs.

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Blood Sometimes Doesn't Clot Properly

  • When you're injured, your blood clots to prevent too much bleeding. Platelets clump together to plug the damaged area. 
  • some substances in food (and drink) affect the way the blood clots: vitamin k, Alcohol and cranberries (may cause blood clotting to slow)
  • Too little blood clotting could mean that your could bleed to death, but too much clotting can cause strokes and deep vein thrombosis.
  • People who are at risk of stroke and DVT can take drugs to reduce the risk. Warfarin, Heparin and aspirin all prevent the blood from clotting.
  • Haemophilia is a condition where the blood doesn't clot properly

Blood Type is important in transfusion

people have different blood groups or types you can be type A, B, O or AB. These letters refer to the type of antigens on the surface of a persons red blood cells. And blood plasma can contain anti-A or anti- B antibodies if an anti A antibody meets an A antigen then the blood clots up and caused problems.

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Blood Groups

Blood Group       Antigens      Antibodies      Can give blood to       Can get blood from

      A                       A                Anti-B               A and AB                  A and O

      B                       B                 Anti-A               B and AB                  B and O

    AB                     A,B             none                 only AB                      anyone

     O                     none           Anit- A/B            anyone                        Only O

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Organ Replacement and Donation

Organs can be replaced by living or dead donors

Living donors can donate whole or parts of certain organs. For example, you can live with just one of your two kidneys and donate the other, or you can donate a piece of your liver. To be a living donor you must be fit and healthy, over 18, and usually a close family member.or someone who has recently died would still work. success rates depend on a lot of things. However there can be problems associated with transplants as the body may reject the new organ.

There issues surrounding organ donation

  • some people think for religious reasons that a persons body should be buried intact.
  • others worry that doctors might not save them if they're critically ill and their organs are needed for transplant.
  • there are also worries that people may get pressured into being a living donor.

Some Mechanical replacements are used outside the body

  • Mechanical replacements can also be used. These don't have the same problems with rejection
  • Sometimes, temporary mechanical replacements are needed to keep someone alive. 
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The Respiratory System

Breathing in and out uses muscles 

  • Your intercostal muscles (between the ribs) and diaphragm contract, and increase the volume of the thorax.
  • A pleural membrane inside the thorax pulls on another pleural membrane attached to the lungs, expanding them- this decreases the pressure inside your lungs, and draws air in.

and Expiration (or breathing out)

  • intercostals and diaphragm relax
  • the thorax volume decreases
  • air is forced out

Lung Capacity can be measured with a spirometer 

Doctors measure lung capacity using a machine called a spirometer- it can help diagnose and monitor lung disease. The patient breathes into the machine for a few minutes, and the volume of air that is breathed in and out is measured and plotted on a graph. Total lung capacity minus resicula volume give you vital capacity the amount of usable air.

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The Lungs

Cilia and Mucus Protect the lungs

  • the respiratory tract (tranchea and bronchi) is lined with mucus and cilia (little hairs) which catch dust and microbes before they reach the lungs.
  • The cilia beat, pushing microbe filled mucus out of the lungs as phlegm.
  • Sometimes the microbes get past the body's defenses and cause infection. The lungs are particularly prone to infections because they're dead end- microbes cant easily be flushed out.
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The Respiratory Systems

In Humans Gaseous Exchange Happens in the Lungs, air enters the body through the mouth or nose, then goes into the trachea (windpipe). Then the trachea splits into two tubes called bronchi each one is a bronchus, one going to each lung. The bronchi split into progressively smaller tubes tubes called bronchioles, and at the end of the line there are small bags called alveoli where the gaseous exchange takes place.

To make gaseous exchange as efficient as possible the alveoli have:

  • a very large surface area
  • a moist surface to help oxygen and co2 dissolve
  • a thin lining so gases dont have to diffuse very far
  • a good blood supply.

Adult amphibians have simple lungs, but their skin also plays an important part in gaseous exchange,

  • oxygen moves into the animal and carbon dioxide moves out through the skin 
  • however this means the skin cant be waterproof, this means the amphibian would lose too much water in a dry environment. 

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The Respiratory Systems


  • gas exchange occurs at the gills. A constant supply of oxygen rich water flows through the open mouth of the fish, and is then forced through the gill slits.
  • Water helps support the gills - it keeps the gill folds separated from each other, if fish weren't in water their gills would stick together and they would suffocate.
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Waste Disposal

The kidneys are excretion organs

  • remove urea from blood, urea produced in the liver from excess amino acids.
  • adjustment of ion levels in the blood
  • adjustment of water content of the blood. 
  • they do this by filtering the blood and reabsorbing useful things with an end product of urine.

Nephrons are the are the filtration units in the kidneys

Ultra filtration 

  • A high pressure is built up which squeezes water, urea, ions and glucose out of the blood and into the capsule.
  • Membranes between the blood vessels and the capsule act like filters, so big molecules like proteins and blood cells are not squeezed out.


All sugars, sufficient ions and sufficient water is reabsorbed. then any left over waste is disposed off as urine 

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Waste Disposal

Water Content is Controlled by Kidneys

  • the amount of water reabsorbed in the kidney nephrons is controlled by a hormone called anti- diuretic hormone (ADH)
  • The brain monitors the water content of the blood and instructs the pituitary gland to release ADH into the blood according to how much is needed.

Urine is not always the same

  • Heat - when its how your sweat causing water loss
  • Exercise- sweat = water loss
  • Water Intake- not drinking enough will concentrate urine saving water.

Dialysis Filters the Blood Mechanically

Patients with kidney failure have a dialysis filter fitted to do the job, Dialysis fluid has the fame concentration of salts and glucose as the blood plasma so they aren't removed from the blood, the barrier is permeable letting ions and waste out but keeping proteins in.

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Menstrual Cycle

  • Stage 1- day 1 is when the bleeding starts. The uterus lining breaks down for about four days.
  • Stage 2- The lining of the uterus builds up again, from day 4 to day 14, into a thick spongy layer of blood vessels ready to receive a fertilized egg.
  • Stage 3- An egg is developed and then released from the ovary at about day 14
  • Stage 4- The wall is then maintained for about 14 days, until day 28. If no fertilized egg has landed on the uterus wall by day 28 then the spongy lining starts to break down again and the whole cycle starts over.

FSH (follicle- stimulating hormone)

  • Produce in the pituitary gland.
  • causes an egg to develop in one of ovaries
  • Stimulates the ovaries to produce oestrogen.


  • Produced in the ovaries 
  • causes the lining of the uterus to thicken and grow
  • stimulates the production of LH and inhibits production of FSH.
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The Menstrual Cycle Part 2

LH (luteinising hormone) 

  • Produced by the pituitary gland.
  • Stimulates the releases of an egg at day 14.


  • Produced in the ovaries.
  • Maintains the lining of the uterus. When the level of progesterone falls, the lining breaks down.
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Infertility Treatment

Infertility can be treated in different.

  • Artificial Insemination- this is where a man's sperm is placed into woman's uterus without having sex. It's used if there if there's some kind of problem with the sperm reaching the egg, or if the man suffers from certain kinds of infertility. Sperm from a donor can also be used if necessary.
  • FSH injections- some women have very low levels of the hormone FSH. This means that their eggs don't develop properly, so they can't get pregnant. FSH injections help to increase fertility.
  • In vitro fertilization- this is where a womans eggs are fertilized outside the body. The woman is given hormone to stimulate egg production. Several eggs are then collected and mixed with the mans sperm and a few fertilized eggs are planted back into the woman's uterus. 
  • Ovary transplants- some women don't have ovaries or they have damaged ones that don't produce any eggs. A relatively new way to treat is to transplant a healthy ovary donated by someone else. It's pretty rare at the moment but could become a more common treatment.
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Infertility Treatment

Not everyone agrees with fertility treatment

  • There's the argument that its just not natural - if you cant have a child, it wasn't meant to be.
  • In IVF not all the fertilized eggs are implanted back into the woman. Some people think that throwing away these extra fertilized eggs is denying a life and so morally wrong.
  • IVF increases the chance of multiple pregnancies. This can be a danger to the mothers health and possibly a financial burden to the parents.
  • What happens if the surrogate mother doesn't want to give up the child.

Feotuses can be screened to see if they're healthy 

  • Amniocentesis - doctors use a long needle to remove some of the fluid that surrounds the baby. This contains skin cells, and the DNA in these can be analysed.
  • Another method involves taking a sample of the placenta. Its more risky than amniocentesis but can be done earlier on in the pregnancy.
  • ethical issues, if the foetus has a genetic defect, is it right to have an abortion.
  • Or might minor defects such as a cleft lip become ground abortion.
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Growth is influenced by many things:

  • Diet is important especially for children who are growing. A poor diet, particularly if its low in proteins (needed to make new cells) or minerals ( for bone growth), may mean that a child doesn't grow as much as its genes would allow.
  • Exercise can also affect growth. Exercise builds muscle, and weight- bearing exercise can increase bone mass. Exercise also stimulates the release of growth hormone.
  • growth hormone is produced by the pituitary gland situated on the underside of the brain.

A baby growth is monitored 

  • A baby growth is regularly monitored after birth to make sure its growing normally. Three measurements are taken- length, mass and head circumference. These results are plotted on average growth charts, like this..
  • The chart shows a number of percentiles. the 50th percentile show the mass that 50% of babies will have reached at a certain age.
  • Babies vary in size, so doctor aren't usually concerned unless a baby's size is above the 98th percentiles or belwow the 2nd percentile, or if there's an inconsistent pattern 
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People live longer than they used to:

  • Life expectancy in the UK has increased loads over the last century. 
  • medical advances mean previously fatal condition can treated.
  • places of work and housing are much safer and healthier.
  • people are better off and can afford a healthier diet and lifestyle.
  • there's much more information available about health issues.

There are problems that come with people living longer 

  • a baby growth is regularly monitored after birth to make sure its growing normally. Three measurement are taken length, mass head circumference. These results are plotted on average growth charts.
  • The chart shows a number of percentiles e.g. the 50th percentile shows the mass that 50% of babies will have reached at a certain age.
  • Babies vary in size so doctors arnt too worried unless the babys size is above the 98th percentile.
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Love these notes ! Simple and precise ;)

Kieran Sieluzycki

Thank you!

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