Human Organ Systems

Question 1

Describe the role of the veins and arteries, and how blood circulates around the body. (12)

Answer 1

Arteries:
Always carry blood away from the heart
Carry oxygenated blood, except for the pulmonary artery
Carry blood under high pressure
Have thick muscular and elastic walls to pump and accommodate blood
A type of supporting tissue called connective tissue provides strength
The channel in the blood vessel that carries blood - the lumen - is narrow

Veins:
Always carry blood to the heart
Always carry deoxygenated blood, except for the pulmonary vein
Carry blood under low or negative pressure
Have thin walls - have less muscular tissue than arteries
Have less connective tissue than arteries
Have a wide lumen

Question 2

What is blood made of and what is the function of each component? (6)

Answer 2

Blood transports materials and distributes heat around the body. It also helps to protect against disease. Blood contains plasma, which is a liquid that the other components of blood are suspended in.

Plasma is a straw-coloured liquid that makes up just over half the volume of blood.

Plasma: Transporting dissolved carbon dioxide, digested food molecules, urea and hormones; distributing heat

Red blood cells: Transporting oxygen

White blood cells: Ingesting pathogens and producing antibodies

Platelets: Involved in blood clotting

Question 3

Describe the role of the lungs, diaphragm, and ribs in breathing. (4)

Answer 3

Inspiration (breathing in)
The diaphragm contracts and moves downwards. The intercostal muscles contract and move the ribs upwards and outwards. This increases the size of the chest and decreases the air pressure inside it which sucks air into the lungs.

Expiration (breathing out)
The diaphragm relaxes and moves back to its domed shape. The intercostal muscles relax so the ribs move inwards and downwards under their own weight. This decreases the size of the chest and increases the air pressure in the chest so air is forced out of the lungs.

Question 4

How are the lungs and alveoli adapted to gaseous exchange? (4)

Answer 4

The alveoli are adapted to make gas exchange in lungs happen easily and efficiently. Here are some features of the alveoli that allow this:

they give the lungs a really big surface area
they have moist, thin walls (just one cell thick)
they have a lot of tiny blood vessels called capillaries

Question 5

What are the stages in human development from fertilised egg to death? (6)

Answer 5

There are six stages in the human life cycle:

1. Foetus
   At this time, a baby is growing inside its mum’s womb.
2. Baby
   A baby is born after spending nine months inside the womb.
3. Childhood
   At this stage, you learn to walk and talk.
4. Adolescence
   Children become teenagers.
5. Adulthood
   Your body is fully developed.
6. Old age
   The last stage in the life cycle of a human.

Question 6

What are the organs of the male (8) and female (7) reproductive system.

Answer 6

Male: Bladder, Glands, Sperm Duct, Urethra, Penis, Testis, Foreskin, Scrotum.
Female: Oviduct, Ovary, Uterus, Cervix, Bladder, Urethra, Vagina.

Question 7

Distinguish between and describe sexual and asexual reproduction. (8)

Answer 7

Sexual reproduction involves two parents and the joining of male and female gametes during fertilisation. The offspring inherit a mixture of genes from both parents, so are different to each other and their parents.

The advantages of sexual reproduction:

produces genetic variation in the offspring
the species can adapt to new environments due to variation, which gives them a survival advantage
a disease is less likely to affect all the individuals in a population

In asexual reproduction there is only one parent. The offspring are clones of the parent and each other.

The advantages of asexual reproduction include:

the population can increase rapidly when the conditions are favourable
only one parent is needed
it is more time and energy efficient as you don’t need a mate
it is faster than sexual reproduction

The disadvantages of sexual reproduction:

time and energy are needed to find a mate
it is not possible for an isolated individual to reproduce
The disadvantages of asexual reproduction include:

it does not lead to genetic variation in a population
the species may only be suited to one habitat
disease may affect all the individuals in a population

Question 8

Define and describe puberty in males and females. (6) Define and describe adolescence. (2)

Answer 8

Boys
Here are some changes that happen only to boys:

voice breaks (gets deeper)
testes and penis get bigger
testes start to produce sperm cells
shoulders get wider
hair grows on face and chest

Girls
Here are some changes that happen only to girls:

breasts develop
ovaries start to release egg cells (the menstrual cycle starts)
hips get wider

Adolescence is the period following the onset of puberty during which a young person develops from a child into an adult.

Question 9

What are the stages of the menstrual cycle? (4)

Answer 9

1: Bleeding from the vagina begins. This is caused by the loss of the lining of the uterus. This is called menstruation or having a period.
5: Blood loss stops. The lining of the uterus begins to re-grow and an ovum starts to mature in one of the ovaries.
14: Ovulation occurs. The ovum travels through the oviduct towards the uterus.
28: If the ovum does not join with a sperm cell in the oviduct, the lining of the uterus begins to break down again and the cycle repeats.