External defences 4/02

How is acid an external defense in the digestive tract?

hydrochloric acid is found in the stomach and destroys pathogens in food and drink

How does mucus membranes in digestive tract serve as an external defence?

exists on most body cavities such as urinary and reproductive tracts and secretes mucus which trap particles and prevent their entry into the digestive system

How does mucus membranes in the urogenital tract serve as an external defence?

exist on most body cavities including digestive and respiratory tract and secrete mucus which trap particles and prevent entry into the urogenital tract, the penis contains very small mucus membrane whilst the vagina has a larger membrane.

How do acids in the urogenital tract serve as an external defence?

vaginal fluid has a low pH of approx 4 and is caused by bacteria lactobacillus that secrete lactic acid, the low pH destroys pathogenic bacteria that enter the urogenital tract

how does movement of fluids in the urogenital tract act as an external defence?

urine flowing through the urethra will expel any pathogens and prevent them from reaching major organs. tears, sweat and saliva are also methods of flushing out pathogens

how does mucus membranes act as an external defence in respiratory system?

exist on most body cavities (including digestive and urogenital tract). they secrete mucus which trap particles and prevent their entry into the lungs

How does the cilia serve as an external defence in the respiratory system?

small hair like projections sweep in a wave like motion to move mucus containing trapped pathogens up the respiratory tract, away from the lungs that may be coughed up or swallowed

How does the hairs serve as an external defence in the respiratory system?

hairs line the nasal passage and ear canal and aid in trapping foreign particles as they enter the nasal cavity and prevent their entry into the respiratory system

How does the lysozyme serve as an external defence in the respiratory system?

an enzyme that destroys bacteria is found in the nasal secretions as well as in tears, saliva and sweat

how does cerumen serve as an external defence in the ear?

stick, slightly acidic substance that contains lysozyme and will trap, inhibit growth and destroy pathogens in the ear

How does lysozyme act as an external defence in the eye?

an enzyme that destroys bacteria is found in tears, as well as in nasal secretions, saliva and sweat

How does movement of fluids act as an external defence in the eye?

constant watering of the eyes will expel any pathogens and prevent them from reaching major organs. urine, sweat and saliva are also methods of flushing out pathogens

what do protective reflexes do

remove foreign pathogens quickly if they enter the body before causing harm

why would sneezing occur?

irritation of the walls of the nasal cavity

why would coughing occur

irritation in lower respiratory tract

why would vomiting occur

irritation of excessive stretching in stomach

why would diarrhoea occur

irritation in small and large intestine

What does the skin serve as to prevent entry of pathogens

physical barrier to prevent entry of pathogens

what does the skin contain to stop pathogenic bacteria

it contains natural bacteria that serve to outcompete and prevent pathogenic bacteria from colonising the skin

what sebum does the skin have

sebum is secreted by oil glands in the skin which contains acids which keep the pH of skin low preventing bacterial growth

how is sweat an external defence for skin?

it is secreted by sweat glands and contains salts and fatty acids to make it harder for bacteria to survive as well as producing natural bactericidal proteins and lysozyme, the movement of sweat also aids in flushing out bacteria

List the external defences of the digestive tract

acids and mucus membranes

List the external defences of the urogenital tract

mucus membranes, acids and movement of fluids

List the external defences of the respiratory system

mucus membranes, cilia, hairs, lysozyme

List the external defences of the eye

lysozyme, movement of fluids