B5 - The Living Body

Internal skeleton: 

• provides internal framework
• grows with the rest of the body
• flexible due to many joints
• allows easy attatchment of muscles

Ossification: cartilage slowly replaced by bone (depositation of calcium and phosphorous) - bones and cartilage are both living tissue so can mend themselves

Osteoporosis: condition commonly found among old people where their bones are prone to fracturing because they lack calcium and phosphorous

Synovial joints = ball and socket, and hinge joints (contain synovial fluid and membrane, ligaments and cartilage)

• synovial fluid: acts as a cushion against shock
• synovial membrane: holds in the synovial fluid
• cartilage: protects the bone head
• ligaments: hold the bones in place

As blood flows through the veins the blood pressure decreases so that the capillaries aren't damaged, veins have valves to ensure no backwards flow.

Cardiac cycle:

• muscles of 2 atria contract while muscles from 2 ventricles relax to receive blood through atrio-ventricular valves which prevent back-flow to the atria
• then muscles of 2 ventricles contract to force blood to the lungs or body, semi-lunar valves prevent back-flow to the ventricles

The 2 pacemakers:

• Sino-atrial node (SAN) make impulses that cause the atria to contract and stimulate the AVN
• Atrio-ventricular node (AVN) make impulses that cause the ventricles to contract

Electrocardiogram: shows changes in electrical impulses in heart muscles

Echocardiogram: displays a video of the heart in action

Hole in the heart: babies have one because their lungs don't function until birth so they don't need a double circulatory system, it should close at birth. If it does not close then oxygenated and deoxygenated blood mix resulting in the artrial blood not carrying enough oxygen - this will starve muscles of oxygen and you will have less energy.

Advantages of artificial pacemakers:

• keeps partients alive and improves quality of life
• no risk of rejection from donor so dont have to use immuno-suppresive drugs
• no problems of donor shortage finding tissue matches

Haemophilia: a condition where you are at risk of internal bleeding from the slightest knock

Agglutination: takes place when two blood groups are not compatable:

• proteins = antigen A and antigen B - on surface of RBC's
• antibodies = anti-A and anti-B - in blood plasma
• anti A will react with antigen A, anti B will react with antigen B

Amphibians and fish: Amphibians are susceptible to water loss due to permeable skin but use their skin to obtain oxygen. Fish gills obtain oxygen by water being forced over filaments

Breathe in: ribs up and out, diaphragm down, volume increase and pressure decrease (breathe out is opposite)

Total lung capacity consists of:

• tidal air - amount of air normally breathed in and out at rest
• vital capacity - max amount of air exchanged
• residual air - amount of air which cannot be forced out of lungs

Gas exchange: takes place by diffusion between the alveoli and air in air sacs, occurs because concentration of oxygen in air = higher than in the deoxygenated blood capillaries

Exchange surfaces: large surface area, good blood supply, permeable, moist, 1 cell thick

Respiratory diseases: asbestosis, cystic fibrosis, lung cancer and asthma (book)

Physical digestion: food passes easily through digestive system and has larger surface area for chemical dygestion.

• starch --> (first to maltose - 2 units) then glucose (1 unit) -  (by carbohydrase in mouth)
• protein --> amino acids - (by protease in stomach - low pH)
• fat --> glycerol and fatty acids - (by lipase in small intestine - bile released to emulsify fats increasing their surface area for efficient digestion)

Chemical digestion requires enzymes of different pH's.

Digested carb and protein molecules (glucose and amino acids) - soluble so diffuse through walls of small intestine into blood

Digested fat molecules (fatty acids) - insoluble so would block blood vessels, diffuse through walls of small intestine into lymph

Small intestine has large surface area:

• many villi in the walls of small intestine
• many microvilli from walls of villi

Blood containing waste (such as urea) enters each kidney by the renal artery. Blood without waste leaves by the renal vein. Each kidney has an outer cortex and an inner medulla. Waste removed from the kidney leaves through the ureters as urine. Each kidney has millions of microscopic kidney tubules (nephrons) which have:

• network of capillaries (glomerulus) surrounded by a capsule = filtration unit
• region where some materials (such as glucose) are selectively reabsorbed
• region where reabsorbtion of some salt and water takes place (amount depends on body demands)

Dialysis machine: used incase of kidney failure, removes urea and regulates sodium levels

• urine quantity increases = urea concentration decreases (drinking lots of water)
• urine quantity deacreases = urea concentration increases (strenuous exercise or hot conditions due to water loss by sweating

Pituitary gland produces anti-deuretic hormone to control conc' of urea by increasing permeablility of kidney tubules (more water absorbed) and using negative feedback mechanism (control ADH production

4 sex hormones:

• FSH - (follicle stimulating hormone) stimulates and egg to develop in an ovary
• LH - (luteinising hormone) controls ovulation (egg release)
• Progesterone - maintains uterus wall
• Oestrogen - repairs the uterus wall

FSH and LH released from pituitary gland --> negative feedback mechanisms control levels of hormones in menstrual cycle - cycle triggered by the receptors in the hypothalamus --> no fertilisation = levels of progesterone and oestrogen decrease -->  when oestrogen and progesterone levels are low, menstruation occurs --> a message is sent to the hypothalamus that hormones levels are low and the cycle begins again --> if fertilisation occurs, the levels of progesterone remain high and no FSH is produced so no more eggs develop and unterus lining doesn't break down.

• Artificial sex hormones prevent ovulation by tricking the body into thinking it's pregnant so no FHS is released and eggs are not stimulated to develop.
• AID, AIH, IVF, surrogacy and ovary transplants - all have medical, moral and expense issues

Foetal screening can be done by: amniocentesis (extracting and testing cells in the amniotic fluid), chromosomal analysis (using a blood test to check chromosomes for abnormalities) - moral issues about interfering with natural processes and whether foetus has right to life, also small risk when exposing foetus.

• calcium, phosphorous, vitamin D and proteins can increase growth
• height extremes are caused my hormone imbalance or genes
• a babies head grows fastest, their growth is monitored to check for abnormalities
• human growth hormone produced by the pituitary gland and stimulates general growth, especially in long bones

Human life expectancy has increased due to: (but bigger burden on pension and nhs funds)

• fewer deaths from industrial disease
• better housing (fewer cases of TB etc)
• healthier diet + lifestyle
• advances in modern medicine such as antbiotics and transplants

mechanical replacements have problems such as: need for power supply, properties of materials used, large size and body reactions to foreign materials

a living person can donate blood, bone marrow and a kidney

organ donation has issues about human rights, surgery on a dead body and acceptance that someone died for the organ to be donated.

transplants require immuni-suppresive drugs to avoid rejection but weaken the immune system