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Anatomy, physiology and pathology of the kidney

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Title: Anatomy, physiology and pathology of the kidney


1
Anatomy, physiology and pathology of the kidney
  • Dr Andrew Potter
  • Registrar
  • Department of Radiation Oncology
  • Royal Adelaide Hospital

Medical ppt
http//hastaneciyiz.blogspot.com
2
Anatomy
3
Overview
  • Retroperitoneal, paired organs
  • Posterior abdominal wall, largely under cover of
    costal margin
  • Key organ of urinary system
  • Filtration/ concentration of urine
  • Biochemical balance, hormone production

4
Structure - macro
  • Enclosed in a strong fibrous capsule which passes
    over the lips of the sinus and becomes continuous
    with the walls of the calices.
  • Kidney capsule are surrounded by pararenal fat
  • Each kidney has superior and inferior poles,
    medial and lateral borders/margins and anterior
    and posterior surfaces
  • Reddish-brown in colour when fresh colour
    varies between cortex and medulla
  • Measure 12x6x3cm (left often slightly longer
    than right)
  • Weigh 130g each
  • Ovoid in outline but indented medially (the renal
    sinus) ? bean-shaped appearance

5
Structure - macro
  • Hilum
  • At the concave part of each kidney
  • Renal vein exits (anteriorly)
  • Renal artery enters (posterior to renal vein)
  • Renal pelvis exits (posterior to artery)

6
Structure - macro
  • Renal pelvis
  • Funnel-shaped
  • Lined with transitional epithelium with a smooth
    muscle and connective tissue wall
  • Continuous inferiorly with ureter
  • Divides into major and minor calyces
  • Urine ? collecting tubule ? minor calyx ? major
    calyx ? renal pelvis ? ureters ? bladder

7
Structure - macro
  • Cortex
  • Beneath capsule, extends towards the pelvis as
    renal columns lying between pyramids of medulla
  • Apices of several pyramids open together into a
    renal papilla, each of which projects into a
    renal calyx

8
Structure - macro
9
Strcuture - micro
  • Nephrons
  • Functional and histological subunit
  • 106 per kidney
  • glomerulus tubules
  • glomerulus
  • tuft of capillaries surrounded by podocytes
  • projects into Bowmans capsule
  • tubule system
  • epithelium continuous with Bowmans capsule
  • proximal convoluted tubule ? Loop of Henle ?
    distal convoluted tubule ? collecting tubule and
    collecting duct
  • glomeruli and convoluted tubules are in cortex
  • ducts lie in the medulla
  • glomerular capillaries supplied by afferent
    arteriole and drained by efferent arteriole

10
Structure - micro
11
Structure - micro
12
Structure - nephron
13
Position and relations
  • Lie in a mass of fat (perinephric fat) and
    fascia, retroperitoneally against posterior
    abdominal wall
  • Fatty renal capsule is covered by fibroareaolar
    tissue the renal fascia
  • Renal fascia
  • encloses kidney, its surrounding fibrous and
    fatty capsules
  • helps maintain organ position
  • superiorly, is continuous with fascia of inferior
    diaphragm
  • medially the left and right fascia blend with
    each other anterior to abdominal aorta and IVC
  • posterior layer of fascia blends with fascia
    overlying psoas
  • Extraperitoneal fat outside the renal fascia is
    located between peritoneum of posterior abdominal
    wall and renal fascia

14
Position and relations
15
Surface anatomy
  • Superior poles protected by 11th and 12th ribs
  • Extend from T12 to L3 vertebral bodies
  • Move 2cm superior-inferior during respiration
  • Right just below transpyloric plane, 5cm right
    of midline. Inferior pole finger-width superior
    to right iliac crest
  • Left just above transpyloric plane, 5cm left of
    midline.

16
Arterial supply
  • Renal arteries
  • branches of aorta at L1/L2 lie behind pancreas
    and renal veins
  • Enter at hilum, giving rise to
  • Anteriorly apical, upper, middle and lower
    segments
  • Posteriorly posterior segment
  • No communication between segments

17
Venous drainage
  • Renal veins
  • Communicate widely
  • Eventually form 56 vessels that unit at the hilum
  • Drain into IVC

18
Lymphatic drainage
  • Para-aortic nodes at L1/L2
  • Surface of upper kidney drains through diaphragm
    into nodes in the posterior mediastinum

19
Innervation
  • Sympathetic
  • Preganglionic cells in spinal cord T12/L1 ?
    fibres to thoracic and lumbar splanchnic nerves
  • Postganglionic cells in coeliac, renal and
    superior hypogastric plexuses
  • Vasomotor function

20
Development
  • Arises from mesoderm
  • Pronephros
  • Transitory, non-functional structures consisting
    of a few ducts which persist
  • Mesonephros
  • Large elongated organs that function as interim
    kidneys
  • Glomeruli tubules open into mesonephric ducts
  • Metanephros
  • Permanent kidneys
  • Begin to develop in 5th week
  • Arises caudal to mesonephros
  • Induces a bud from caudal end of mesonephric duct
    (ureter)
  • Ureteric bud divides into calyces of pelvis and
    collecting tubules and medullary pyramids
  • Develops in anatomic pelvis and migrates to adult
    position and the new single definitive artery
    forms

21
Physiology
22
Physiology - overview
  • Regulation of the water and electrolyte content
    of the body
  • Retention of substances vital to the body such as
    protein and glucose
  • Maintenance of acid/base balance
  • Excretion of waste products, water soluble toxic
    substances and drugs
  • Endocrine functions

23
Water and electrolyte regulation
  • Renal blood supply is approx 20 of cardiac
    output
  • 99 to cortex
  • 1 to medulla
  • 2 capillary beds, arranged in series
  • Glomerular
  • High pressure for filtering
  • Peritubular
  • Low pressure for absorption

24
Water and electrolyte regulation
  • Urine formation - 3 phases
  • Simple filtration
  • Selective and passive resorption
  • Concentration

25
Filtration
  • Takes place through the semipermeable walls of
    the glomerular capillaries
  • almost impermeable to proteins and large molecule
  • Glomerular filtrate is formed by squeezing fluid
    through glomerular capillary bed
  • Hydrostatic pressure (head of pressure) is
    controlled by afferent and efferent arterioles,
    and provided by arterial pressure
  • About 20 of renal plasma flow is filtered each
    minute (125 ml/min). This is the glomerular
    filtration rate (GFR).
  • Autoregulation 
  • With a change in arterial blood pressure, there
    is constriction or dilatation of the afferent and
    efferent arterioles, the muscular walled vessels
    leading to and from each glomerulus

26
Juxtaglomerular apparatus
  • Macula densa cells
  • Detect chloride concentration
  • Juxtaglomerular cells
  • Modified smooth muscle cells
  • Produce renin
  • Converts angiotensin to angiotensin I
  • Angiotensin I converted to angiotensin II by
    Angiotensin converting enzyme (ACE)
  • Causes systemic vasoconstriction and increase in
    BP

27
Tubular reabsorption
  • 60 of solute is reabsorbed in proximal tubule
  • Different parts of tubule system optimised to
    absorb different components of urine
  • Distal tubule and collecting duct determines
    final urine concentration
  • Regulated by ADH production by posterior pituitary

28
Acid-base balance
  • Tubular acid secretion
  • Ammonia secreted by tubules (combines with H to
    form NH4 and passed in urine)

29
Hormones
  • Renin
  • Increases production of angiotensin II
  • Aldosterone
  • Stimulates water and sodium ion resorption in
    distal tubule
  • Atrial natriuretic hormone (ANP)
  • Produced when atrial pressure increases (eg heart
    failure)
  • Promote Na, Cl- and water loss
  • Antidiuretic hormone
  • Increases permability of distal tubule to water,
    to cinrease water resorption (therfore increases
    concentration of urine)
  • 1,25 dihydroxy vitamin D3
  • Promotes calcium absorption from gut
  • Erythropoietin (EPO)
  • Stimulates marrow to produce red blood cells

30
Pathology
31
Benign pathology
  • Vascular disease
  • Hypertension, diabetes, deposition of immune
    complexes (eg amyloidosis), coagulation
  • Inflammatory/autoimmune conditions
  • SLE
  • Infective
  • Pyelonephritis, tuberculosis
  • Idiopathic
  • Nephrotoxic drugs - eg. platinum chemotherapy,
    aminoglicoside antibiotics
  • Congenital/structural
  • Polycystic kidney, horseshoe kidney, renal
    agenesis/hypoplasia
  • Metabolic/biochemical
  • Renal calculi

32
Benign tumours
  • Frequent incidental findings (up to 20)
  • Renal adenoma
  • Bening epithelial tumours arising from tubular
    epithelium
  • Difficult to distinguish from renal cell
    carcinoma - similar histology
  • Distinguished on size (lt3cm)

33
Benign tumours
  • Oncocytomas
  • Variant of adenoma
  • Angiomyolipoma
  • Smooth muscle, fat and vessels
  • Renal fibroma
  • Common small tumours
  • 3-10mm
  • Arise in medulla

34
Malignant tumours
  • 90 are renal cell adenocarcinoma (RCC)
  • About 3 of all adult cancers
  • Usually seen gt50 years of age
  • Present with haematuria, pain, loin mass
  • Paraneoplastic syndrome
  • Hypercalcaemia, hypertension, polycythaemia,
    Cushings syndrome or other hormonal disturbances

35
Renal cell carcinoma
  • Rounded masses, yellowish colour with haemorrhage
    and necrosis
  • Most commonly the clear cell variant
  • Clear cytoplasm because of high lipid and
    glycogen content

36
Renal cell carcinoma
  • Spread by local extension/expansion through
    capsule
  • Blood borne metastases
  • Bone, lung, brain
  • Lymphatic metastases
  • Para-aortic chain
  • Prognosis depends on stage
  • 70 ten-year survival of confined to renal
    capsule
  • Poor prognosis if metastatic disease at
    presentation

37
Nephroblastoma (Wilms tumour)
  • Common childhood malignancy
  • Embryonal tumour from primitive metanephros
  • Peak incidence 1-4 years of age
  • Presents as abdominal mass or haematuria
  • Rounded mass largely replacing kidney
  • Solid, fleshy white with necrosis
  • Prognosis related to stage at presentation

38
Summary
  • Paired retroperitoneal/post abdominal organ
  • Cortex, medulla, nephron
  • Glomerulus, tubule, duct
  • Water/biochemical regulation
  • Filtration, reabsorption
  • Hormone production
  • Many benign pathological conditions
  • Malignancies predominantly RCC in adults,
    nephroblastoma in children

39
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