chapter 19 - homeostasis (part 3)

7/30/2019 Chapter 19 - Homeostasis (Part 3)

1/66

HOMEOSTASIS

Powerpoint@lecture Slides Are Prepared By Biology Lecturer, KMPk
mailto:point@lecturemailto:point@lecture


2/66

19.3 : HUMAN HOMEOSTATIC ORGANS: LIVER AND

KIDNEY

9.3.2 Structure and functions of Kidney

TOPICS


3/66

PREVIOUS LESSON


4/66

PREVIOUS LESSON


5/66

OBJECTIVES

At the end of this lesson, students should be able to:

11. Describe the structure of kidney & its functional units.

2. Describe urine formation:

i) Ultrafiltration

ii) Reabsorption

iii) Secretion

3. Describe the concentration of urine by counter current

multiplier mechanism


6/66

19.3.2 Structure and

Functions of Kidney

A major excretory and osmoregulatory organ

A pair, bean-shaped organ

About 10 cm in length


7/66

Situated towards the back of

the lower part of the

abdominal cavity

Left kidney is slightly higherthan the right

Protected by a capsule offibrous connective tissue

Rich blood supply andregulates the bloodcomposition

Contributes to homeostasis


Functions of Kidney


8/66

Consists of:

Renal cortex

A light outer region

Renal medulla

A dark inner region

Renal pelvis

A whitish central

region

Leads to ureter


Functions of Kidney


9/66

The basic structural and

functional unit of the

kidney

Microscopic excretory

tubules

Packing the cortex and

medulla region

NEPHRON


Functions of Kidney


10/66

Each kidney

consists about a

million nephrons

Total tubulelength: 80 km

Enormous surface

area for the

exchange of

materials


Functions of Kidney


11/66

Structure of a nephron:

Glomerulus

A spherical cluster of

blood capillaries

Bowmans capsule

A double-walled, cup-shaped swelling capsule

Blind end of the tubule

Located in the cortex


Functions of Kidney


12/66

Proximal convolutedtubule

Lumen is continuouswith the Bowmanscapsule

Highly coiled

Located in the cortex


Functions of Kidney


13/66

Loop of Henle

Hair-pin shaped

Have descending

limb & ascending

limb

Located in themedulla


Functions of Kidney


14/66

Distal convoluted

tubule

Located in the

cortex


Functions of Kidney


15/66

Collecting duct

End of kidney

Eventually drain into

the pelvis of thekidney

from where the urine

flows into the ureter

Located in the

medulla


Functions of Kidney


16/66


Functions of Kidney


17/66

17


18/66

18

Main blood vessels

Renal artery : supplies oxygenated blood from

aorta

AortaRenal arteries


Functions of Kidney


19/66

19

Main blood vessels

Renal veins: carries deoxygenated blood to

posterior vena cava

Vena cavaRenal veins


Functions of Kidney


20/66

20

AortaRenal arteries

Vena cavaRenal veins


Functions of Kidney


21/66

21

An Individual Nephronand Its Blood Supply

Renal artery

afferent arteriole

Glomerulus

efferent arteriole

vasa recta


Functions of Kidney

Renal vein


22/66

Urine formation :

22

1.Ultrafiltration

2. Reabsorption

3. Secretion


Functions of Kidney


23/66

23

.Ultrafiltration

2.Reabsorption

3.Secretion

URINE FORMATION


24/66

24


25/66

25

Takes place in the glomerulus

and the Bowmans capsule

Occurs due to the hydrostatic

pressure caused by the bloodpressure

1. ULTRAFILTRATION

URINE FORMATION


26/66

26

Blood enters the glomerulus

via afferent arteriole (larger

diameter) and leaves via efferent

arteriole (smaller diameter)

Produce high hydrostatic

pressure

ULTRAFILTRATION


27/66

27

Forces small molecules through the walls of capillaries and

Bowmans capsule into the capsular space

Except RBC, plasma proteins and platelets

glucose, amino acids, sodium,

potassium, chloride,

bicarbonate, other salts, waterand urea,

ULTRAFILTRATION


28/66

28

The wall of Bowmans capsule

consists of a specialized

epithelial cell called

podocytes (pod:foot)

Have numerous

cytoplasmic extension

called foot

Cover most of the

capillaries

STRUCTURE OF

BOWMANS CAPSULE


29/66

29

Foot processes of adjacent podocytes are separated by

narrow gaps

Filtration slits

STRUCTURE OF

BOWMANS CAPSULE


30/66

30


31/66

31

The perforated walls of the capillaries and thepodocytes form a filtration membrane

Permits fluid and small solutes to pass

glomerular filtrates

STRUCTURE OF

BOWMANS CAPSULE


32/66

32

STRUCTURE OF


33/66

33

STRUCTURE OF

BOWMANS CAPSULE


34/66

34

The process ofabsorbing useful substances into

capillaries which wrapped around tubule

Glucose, amino acids, vitamins, most of the water,

sodium and chloride ions

2. REABSORPTION

Tubules Blood capillaries

URINE FORMATION


35/66

35

REABSORPTION

Occurs in:

Proximal convoluted tubule

Loop of Henle

Distal tubule

Collecting duct


36/66

36


Most reabsorption occurs : over 80%

All glucose, amino acids,

vitamins and hormones85% of NaCl and other ions

Active transport

REABSORPTION


37/66

37


40-50% of urea

85% of water

As concentration of ions increase in plasmaWater moves out

Diffusion

Osmosis

REABSORPTION


38/66

38

STRUCTURE OF


39/66

39

STRUCTURE OF

PROXIMAL TUBULE


40/66

40

Loop of Henle

Function:oTo create a water potential gradient

oBetween the filtrate and the interstitial fluid in the

medulla

Longer : urine produced is more concentrated

REABSORPTION

STRUCTURE LOOP OF


41/66

41

Divided into 2:

Descending limb

Ascending limboThin segment

oThick segment

STRUCTURE LOOP OF

HENLE


42/66

42

Descending limb

Thin walls

Highly permeable towater

Impermeable to NaCl and

other solutes

REABSORPTION


43/66

43

Ascending limb

Thick segment

Thin segment

- thick wall

- transport NaCl actively

- thin wall

- transport NaCl passively

-impermeable to water

- permeable to NaCl

and urea

REABSORPTION


44/66

44


45/66

45

Involves counter-current multiplier mechanism

Counter-currento

Filtrate past each other in opposite directionsoThe descending and ascending limb

REABSORPTION


46/66

46

Involves counter-current multiplier mechanism

Multiplier

oFiltrate flow down the descending limboHigh concentration of NaCloMost hypertonic round the hairpin

Filtrate flow up the ascending limboLess concentration of NaCloHypotonic

REABSORPTION


47/66

47

In the descending limb,

Water is drawn out by

osmosis Concentrates NaCl in the

tubule

Filtrate concentration is

highest at the bottom of

the loop of Henle

REABSORPTION


48/66

48

As the filtrate flows up

the ascending limb

Thin segmentoNaCl passively diffuseout into the interstitialfluid

Thick segmentoNaCl is activelypumped out into theinterstitial fluid

REABSORPTION


49/66

49

As the filtrate flows up the

ascending limb

Produce a high

concentration of NaCl

around the descending

limb

Filtrate concentration islower in the tubule

REABSORPTION


50/66

50

Water potential in the

interstitial fluid is lower

Causes water in the

descending limb drawnout by osmosis

Creating a

concentration gradient

in the medulla

REABSORPTION

REABSORPTION


51/66

51

The water and NaCl

moves into the vasa

recta surroundingthe loop of Henle

REABSORPTION


52/66

52


53/66

53

The Distal Tubule

Receives a hypotonic filtrate

from the ascending limb

Not permeable to water butdepends on hormonal

controloBecomes permeable

under hormonal controloAnti-diuretichormone (ADH)

REABSORPTION


54/66

54

The Distal Tubule

Active reabsorption of

Na+

oUnder hormonal

control

oAldosterone

REABSORPTION


55/66

55

The Collecting Duct

Carries the filtrate from

cortex to medulla to the renalpelvis

Permeability to water and

urea is under hormonal

control

oAnti-diuretic hormone

(ADH)

REABSORPTION


56/66

56

When the filtrate pass

along the collecting duct

Water moves out by

osmosis to the

interstitial fluid

REABSORPTION


57/66

57

ome urea will also

diffuse out

Along with NaCl,contributes to the high

concentration of solute

(lower water potential)

in the interstitial fluid

REABSORPTION


58/66

58

This urea is recycled

by diffusion into the

ascending limb of loop

of Henle

REABSORPTION


59/66

59

REABSORPTION

URINE FORMATION


60/66

60

Occurs in the distaltubule and the

proximal convoluted

tubule Mainly in distal tubule

3. SECRETION

Blood capillaries Tubules

URINE FORMATION


61/66

61

Distal tubule secretes H+ and NH3from the blood into

the filtrate

Helps to maintain blood pH

Secretion of K+occurs under hormonal control:

aldosterone

SECRETION


62/66

62

Proximal & distal tubule also actively

secretes harmful or toxic substances into

the filtrate

Removed by urine

Eg: drugs such as penicillin and caffeine

SECRETION


63/66

63


64/66

64 Figure 26.6


65/66

65


66/66

CONCLUSION

VIDEO FUNCTIONS OF KIDNE
http://c/Documents%20and%20Settings/kmpk/Desktop/homeostasis/Urinary%20system%20-%20The%20nephron%20-%20YouTube.flvhttp://c/Documents%20and%20Settings/kmpk/Desktop/homeostasis/Urinary%20system%20-%20The%20nephron%20-%20YouTube.flv