Body Systems

What is the primary function of gas exchange in all living organisms?

It facilitates the interchange of materials, like oxygen and carbon dioxide, required for metabolic reactions.

Why do cells require oxygen?

Oxygen is required for aerobic respiration, which produces large amounts of chemical energy (ATP).

What challenge do larger, multicellular organisms face regarding diffusion distance for gas exchange?

The distance from the organism's centre to its exterior is greater, necessitating a steeper concentration gradient for adequate exchange.

Larger organisms have a _ surface area to volume ratio, reducing their relative capacity to exchange gases.

smaller

List the five key qualities of respiratory surfaces, as summarised by the mnemonic SMART.

Large Surface area, Moist, Absorptive, Rich blood system, Thin tissue layer.

Why must respiratory surfaces be moist?

Gases diffuse more readily when they are dissolved in a solution.

Why is a rich blood system essential for a respiratory surface?

It maintains a suitable concentration gradient for efficient gas exchange by transporting gases to and from the surface.

Trace the path of inhaled air from the trachea to the site of gas exchange.

Air travels down the trachea, which bifurcates into two bronchi, then divides into bronchioles, and ends in the alveoli.

What is the primary function of the alveoli?

The alveoli function as the site of gas exchange with the bloodstream.

What is the function of Type I pneumocytes in the alveoli?

These extremely flat cells are optimised for gas exchange due to their minimal diffusion distance.

What is the function of Type II pneumocytes in the alveoli?

These cuboidal cells release pulmonary surfactant to reduce surface tension and prevent the alveoli from collapsing.

What is ventilation?

Ventilation is the mechanical process of moving air into and out of the lungs, mediated by antagonistic muscles.

During inhalation, what happens to the diaphragm and external intercostal muscles?

The diaphragm contracts and flattens, and the external intercostal muscles contract, pulling the ribs upwards and outwards.

How does the contraction of muscles during inhalation affect pressure within the lungs?

It increases the volume of the thoracic cavity, causing the pressure within the lungs to become less than atmospheric pressure, drawing air in.

During exhalation, what happens to the diaphragm and internal intercostal muscles?

The diaphragm relaxes and curves upwards, and the internal intercostal muscles contract, pulling the ribs down and inwards.

How does muscle action during exhalation affect pressure within the lungs?

It decreases the volume of the thoracic cavity, causing pressure in the lungs to become greater than atmospheric pressure, forcing air out.

Term: Total lung capacity

The maximal volume of air the lungs can hold.

Term: Vital capacity

The maximal volume of air that can be exchanged (inhaled and exhaled).

Term: Tidal volume

The volume of air exchanged during a normal breath.

Term: Residual volume

The volume of air that is always present in the lungs, even after maximal exhalation.

Trace the general path of blood flow from the heart and back again, starting with arteries.

Arteries branch into arterioles, which lead to capillaries; these pool into venules, which converge to form veins that return blood to the heart.

What is the primary function of erythrocytes (red blood cells)?

To transport oxygen to the body's tissues.

What is the primary function of thrombocytes (platelets)?

To initiate the process of blood clotting.

What is plasma?

The fluid component of blood that is involved in transporting materials such as proteins, glucose, hormones, and waste products.

Describe the typical wall thickness and lumen diameter of an artery.

Arteries have thick walls and a comparatively narrow lumen to withstand and maintain high blood pressure.

Describe the typical wall thickness and lumen diameter of a vein.

Veins have thinner walls and an extremely wide lumen, as blood is at low pressure.

How does the outer layer of collagen in an artery's wall contribute to its function?

It prevents the artery from rupturing under high pressure.

What is the role of the muscle and elastic fibres in the arterial wall?

They allow the artery to stretch and recoil with each pulse, helping to maintain a stable blood pressure.

Why do veins contain valves when arteries do not?

Veins have valves to prevent the backflow of blood, which is necessary because the blood is at a very low pressure.

How does the contraction of skeletal muscles aid blood flow in veins?

Skeletal muscle contractions compress the flexible veins, which helps to propel blood back towards the heart.

How is the structure of a capillary wall adapted for material exchange?

It is extremely thin, composed of a single layer of endothelial cells, which minimises the diffusion distance.

The lumen of a capillary is so narrow that only one _ can pass through at a time, optimising oxygen exchange.

erythrocyte (red blood cell)

What are fenestrated capillaries?

Capillaries that contain pores to improve the transfer of materials between the blood and tissues.

What is the function of the atria in the heart?

They act as reservoirs, collecting blood returning to the heart via veins before passing it to the ventricles.

What is the function of the ventricles in the heart?

They act as pumps, expelling blood from the heart to various body tissues via arteries.

What is the purpose of the pulmonary circulation circuit?

The right side of the heart pumps deoxygenated blood from the body to the lungs to be oxygenated.

What is the purpose of the systemic circulation circuit?

The left side of the heart pumps oxygenated blood from the lungs to all the body tissues.

Why does the left side of the heart have a thicker muscular wall (myocardium)?

It needs to pump blood greater distances (to the entire body) compared to the right side (which only pumps to the lungs).

What is a pulse?

A wave of blood forced through the arteries by each rhythmic contraction of the heart.

What is the function of the coronary arteries?

They form a network of vessels that supply the heart tissue itself with oxygen and glucose.

Term: Atherosclerosis

The hardening and narrowing of arteries due to the deposition of cholesterol, forming fatty deposits called atheromas.

What is a thrombus in the context of coronary heart disease?

A blood clot that forms when an atherosclerotic plaque ruptures, which can restrict or block blood flow.

List four risk factors that can increase the chances of developing occlusions in coronary arteries.

Any four of: Genetics, obesity, diseases (like diabetes), diet (salty/fat-rich), lack of exercise, sex (male), smoking, or age.

Asexual reproduction involves a single parent producing offspring that are genetically ____ to itself.

identical (clones)

What is the main advantage of sexual reproduction?

It produces offspring with new gene combinations, resulting in the genetic variation required for adaptation to a changing environment.

The process of _ creates haploid sex cells (gametes).

meiosis

The fusion of haploid gametes during sexual reproduction is known as _.

fertilisation

What is a zygote?

The genetically distinct diploid cell formed from the fusion of a sperm and an egg cell.

Why is the female gamete (egg cell) significantly larger than the male gamete (sperm)?

The egg provides all the organelles and cellular material for the resulting zygote.

In the male reproductive system, where does sperm production occur?

In the testes.

After production, sperm matures and develops motility in a structure called the _.

epididymis

What does the prostate gland secrete and why?

It secretes an alkaline fluid to neutralise the acidic environment of the vagina.

In the female reproductive system, where does an egg cell develop?

Within a follicle found on the ovaries.

After ovulation, the egg is swept into the _ (fallopian tube) by the fimbriae.

oviduct

What is the endometrium?

The mucous membrane lining the uterus, where a fertilised egg will implant.

What happens to the endometrium if fertilisation does not occur?

It is sloughed away and exits the body as menstrual blood.

In the ovarian cycle, what is the role of Follicle Stimulating Hormone (FSH)?

FSH is secreted from the anterior pituitary and stimulates the growth of ovarian follicles.

The dominant follicle produces estrogen, which inhibits FSH secretion through a _ feedback loop.

negative

What hormonal event triggers ovulation around day 12 of the menstrual cycle?

A large surge of Luteinizing Hormone (LH) and a lesser surge of FSH, stimulated by high estrogen levels.

After ovulation, the ruptured follicle develops into a structure called the _.

corpus luteum

What two hormones are secreted by the corpus luteum?

Progesterone and estrogen.

In the uterine cycle, what is the initial effect of estrogen produced by the follicles?

Estrogen stimulates the thickening of the endometrial layer in the uterus.

What is the combined role of progesterone and estrogen from the corpus luteum on the uterus?

They further support the thickening and maintenance of the endometrial lining.

What causes the endometrium to break down and be shed during menstruation?

If fertilisation doesn't occur, the corpus luteum degrades, stops releasing estrogen and progesterone, and the lining can no longer be maintained.

What is the first step of hormone use in In Vitro Fertilisation (IVF)?

Drugs are used to halt the regular secretion of FSH and LH, arresting the normal menstrual cycle.

What is the purpose of administering artificial hormones in IVF after the natural cycle is halted?

To promote superovulation, which is the development and release of multiple eggs.

After egg extraction in IVF, what happens before implantation?

The eggs are incubated in the presence of a sperm sample and examined for successful fertilisation.