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THE KIDNEY (macroscopic structure)
CHARACTERISTICS
➔ bean shaped
◆ hilum (concave part)
➔ dark red
➔ capsule made of connective tissue
◆ prevents infection
➔ adrenal glands just above
◆ adrenaline
➔ peritoneum & blood vessels keep in place & adipose
◆ protects the kidney
➔ surrounded by organs to wedge it
➔ found in abdominal cavity
FUNCTIONS
➔ filters the unclean blood to clean it of toxins
◆ done by the microscopic unit the nephron
➔ maintains homeostasis
THE NEPHRON (microscopic structure)
NOTES
structural and functional unit
lead to collecting ducts
surrounded by capillaries essential for
reabsorption and excretion of waste
FUNCTION OF THE KIDNEY
Glomerular Filtration- occurs within the bowman's capsule
➔ nitrogenous waste blood enters the wide afferent arteriole
➔ exists through narrow efferent arteriole
◆ this creates pressure (hydrostatic) so that it
happens passively & substances can diffuse through
the glomerular membrane
➔ the filtrate substances are then filtered through the
glomerular membrane
➔ this is known as ultrafiltration
WHAT IS A FILTRATE?
Mainly plasma but also: water, vitamins, amino acids & nitrogenous waste
ADAPTATIONS
➔ glomerular capillary is porous, endothelial cells (easy diffusion); thin
basement membrane
➔ podocytes have filter slits so sub. can diffuse; thin flat cells
➔ surface area increased because of curves
, Tubular Reabsorption- occurs in the convoluted proximal
tubule
PROXIMAL CONVOLUTED TUBULE
➔ useful substances from the filtrate are reabsorbed either actively or
passively into the peritubular capillary
◆ ACTIVELY (move against [ ] gradient) : glucose, proteins;
H2O soluble vitamins
◆ PASSIVELY(goes from high to low [ ] ): H2O, Cl-1, Na+1;
small amounts of urea (small molecule)
ADAPTATIONS
➔ long and coiled for inc surface area for max absorption
➔ lots of capillaries around it for reabsorption
➔ cuboidal epithelial with : microvilli (inc surface area), mitochondria
(ATP for active process)
LOOP OF HENLE
➔ it is divided into 3 segments thin descending, thin
j……….ascending & thick ascending limb
➔ sometimes called the “Salt Pump” as it deals with Na+1 ,
………..Cl-1 & H2O
➔ THIN DESCENDING LIMB:
◆ is permeable to H2O so osmosis occurs because
………………....surrounding tissue is hypertonic
◆ the osmolarity of the filtrate inc
◆ further down the limb the more [ ] the medulla
………………….gets
➔ THIN ASCENDING LIMB:
◆ Na +1 is passively pumped out of the limb
➔ THICK ASCENDING LIMB:
◆ is impermeable to H2O so Na+1 & Cl-1 is actively
………pumped into the medulla and so it becomes hypertonic
ADAPTATIONS
➔ the curve allows for max reabsorption
➔ it is made of squamous endothelial for easy diffusion
Tubular Excretion- occurs mainly is distal convoluted tubule and collecting duct
➔ molecules such as K+1 & H+1 diffused back into filtrate and other harmful sub
➔ Na+1 out of filtrate (done by aldosterone AD) and H2O follows by osmosis
◆ aldosterone controls the amount of salt in blood
➔ H2O passively exits the collecting duct because of [ ] of medulla tissue making urine really [ ]
MAINTAINING HOMEOSTASIS
➔ OSMOREGULATION- controls ratio of H2O & solutes and thus proper body functioning & so it is kept constant
◆ greater [ ] the higher osmolarity thus more osmosis takes place
➔ less fluid the more [ ] urine becomes; more H2O conserved by body
➔ ADH causes collecting duct to become more permeable to H2O so more is conserved by the body
◆ once osmolarity normalises ADH is no longer released
◆ more urine is made after this (negative feedback system)
➔ AD is secreted when drop in Na+1; osmolarity drops & blood volume and pressure is low
◆ more Na+1 is reabsorbed (osmolarity normalises) and H2O follows inc blood volume and pressure
, COMMON RENAL PROBLEMS
DIURESIS (increase in urine output)
➔ DIURETICS- chemicals that increase the output of urine
◆ caffeine- causes vasodilation (when the blood vessels widen) which increases the amount of filtrate
◆ alcohol- causes more ADH to be released which means the volume of urine increases
◆ blood glucose & urea- act as osmotic diuretics & H2O is released with the compound
➔ The disorder of the pituitary lets too little ADH released
◆ This causes diabetes insipidus ( produces a lot of dilute urine)
KIDNEY FAILURE (the kidneys stop working)
➔ this causes a build up of nitrogenous waste that is not expelled from the body
◆ homeostasis cannot be kept as the pH, concentration & H2O balance is not regulated
CAUSES OF KIDNEY FAILURE
➔ injury of the kidney
➔ a severe infection by bacteria the affects the different part of the kidney & usually causes inflammation
➔ bilharzia (parasite) enters the kidney, bladder; liver which damages the organ tissue
➔ excessive use of drugs like paracetamol
WHAT ARE KIDNEY STONES?
➔ crystals of insoluble, solid NaCl
➔ Caused by: too much calcium, too little water, abnormal basic or acidic urine
➔ lithotripsy- is ultrasound waves that are used to shatter the stones so it can pass out with the urine
KIDNEY INJURIES
➔ BLUNT FORCE TRAUMA- direct impact made to abdomen, side of body/ back
◆ can cause bruising of the kidney but best indicator is blood in urine
➔ PENETRATING FORCE TRAUMA- the skin is torn and the damage is usually more severe
The severity of the injury is graded 1-5. One usually being things such as bruising to the kidney. Five would be
lacerations & torn attachments that have cut off the blood supply to the kidney.
DIALYSIS
➔ Short-term solution to kidney failure is cleaning the blood artificially using a machine.
➔ dialysis is the movement of molecules of different composition down a [ ] gradient
DISADVANTAGES
➔ time consuming process: have to go a couple times a week and it lasts
very long.
➔ only the rich can afford it as it is very expensive
➔ can only remove a certain amount of liquid so the patient has to
decrease the amount of liquid they take in
➔ it can not remove phosphates and potassium which can become life
threatening
◆ it then has to be limited from the diet
➔ the patient can feel very ill while the treatment is being done
➔ anticoagulants have to be added prevent clotting which can create
future bleeding problems
Peritoneal Dialysis uses the patient’s peritoneum as the dialysing membrane
IDNEY TRANSPLANT- the long term solution to renal failure
K
➔ it is important for the new kidney to be attached to the renal artery and renal vein
◆ this will ensure it will be purified
➔ there is a chance the kidney could be rejected so medication is often given to decrease these chances but then
risk of infection is increased
, The Structure of the Heart
PULMONARY SYSTEM SYSTEMIC SYSTEM
★ Veins carry oxygen-poor blood
towards the heart
○ irregular shape with a thin muscle layer; few elastic fibres; have
semilunar valves
■ semilunar valves prevent the backflow of blood
★ Arteries carry oxygen-rich blood away from the heart
○ regular shape with a thick muscle layer; have many elastic fibres
★ Capillaries get nutrients to all cells of the body
○ have only a single layer of endothelial cells
The heartbeat- “lub-dup”
Is measured using a stethoscope.
The cardiac muscles are myogenic; so the contraction starts from within the muscle
itself.
1. The Sinoatrial node starts the contraction & sends impulse to contract the
atria.
2. Atrioventricular node is started by the SA node which contracts the ventricles.
3. The Bundle of His splits from AV node into two & runs down septum.
4. The Purkinje fibres are at the base of the heart & spread up ventricles to cause them
to contract.
CONTROLLING OF THE HEART BEAT
★ by the nervous system
○ stimulated by the autonomic nervous system (ANS) controls all things that are not under conscious
control
■ two types : the parasympathetic system & sympathetic system
■ parasympathetic slows down the heart rate
■ sympathetic speeds up the heart rate
○ the medulla oblongata controls these stimulus
★ by hormones
○ they usually take longer than electrical impulses to work
○ they attach to receptors on the cardiac muscles & change the way the muscles contract
■ adrenaline & thyroxine increases the heart rate
★ the pulse is the contraction and expansion of the arteries measured in heartbeats per minute
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