Ch 10 - Homeostasis

Question 1

What are the main functions of the excretory system?

Answer 1

regulation of blood pressure, blood osmolarity, acid-base balance, and removal of nitrogenous waste

Question 2

What do kidneys do?

Answer 2

produce urine

Question 3

What is the pathway for urine?

Answer 3

• made in kidneys
• flows into the ureter at the renal pelvis
• collected in the bladder until it is excreted through the urethra

Question 4

What are the structures in the kidneys?

Answer 4

• contain a cortex and a medulla

- each kidney has a hilum, which contains a renal artery, renal vein, and ureter

Question 5

How does blood flow through kidneys?

Answer 5

• kidneys have a portal system with 2 capillary beds in series
• blood from the renal artery flows into afferent arterioles, which form glomerulus in Bowman’s capsule (the first capillary bed)
• blood then flows through the efferent arterioles to the vasa recta (the second capillary bed), which surrounds the nephron, before leaving the kidney through the renal vein

Question 6

What is the detrusor muscle?

Answer 6

• muscular lining of the bladder

- under parasympathetic control

Question 7

What is the difference between the internal and external urethral sphincter of the detrusor muscle?

Answer 7

• in: consists of smooth muscle and is under involuntary (parasympathetic) control
• ex: consists of skeletal muscle and is under voluntary control

Question 8

What is filtration?

Answer 8

• the movement of solutes from blood to filtrate at Bowman’s capsule
• the direction and rate is determined by Starling forces, which account for the hydrostatic and oncotic pressure differentials between the glomerulus and Bowman’s space

Question 9

What is secretion?

Answer 9

the movement of solutes from blood to filtrate anywhere other than Bowman’s capsule

• blood to filtrate (remove HUNK)
• increase protein intake = increase NH3, urea secretion
• decreased blood pH = increase H+ secretion
• excess waste too large for glomerulus

Question 10

What is reabsorption?

Answer 10

the movement of solutes from filtrate to blood

Question 11

What is the proximal convoluted tubule (PCT)?

Answer 11

• the site of bulk reabsorption of glucose, amino acids, soluble vitamins, salt, and water (controls solute identity)
• also the site of secretion for H ions, K ions, NH4+, and urea

Question 12

What is the descending limb of the loop of Henle?

Answer 12

• permeable to water but not salt; therefore, as the filtrate moves into the more osmotically concentrated renal medulla, water is reabsorbed from the filtrate
• the vasa recta and nephron flow in opposite directions, creating a countercurrent multiplier system that allows maximal reabsorption of water

Question 13

What is the ascending limb of the loop of Henle?

Answer 13

• permeable to salt but not water; therefore, salt is reabsorbed both passively and actively
• the diluting segment is in the outer medulla; because sault is actively reabsorbed in this site, the filtrate actually becomes hypotonic compared to the blood

Question 14

What is the distal convoluted tubule (DCT)?

Answer 14

a responsive to aldosterone and is a site of salt reabsorption and waste produce excretion, like the PCT

Question 15

What is the collecting duct?

Answer 15

responsive to both aldosterone and ADH and has variable permeability, which allows reabsorption of the right amount of water depending on the body’s needs

Question 16

How are the kidneys under hormonal control?

Answer 16

when blood pressure (and volume) are low, 2 different hormonal systems are activated (aldosteron and ADH)

Question 17

What is aldosterone and how does it affect blood pressure and osmolarity?

Answer 17

• a steroid hormone regulated by the renin-angiotensin-aldosterone system that increases sodium reabsorption in the DCT and collecting tube, thereby increasing water absorption
• this results in an increased blood volume (and pressure), but no change in osmolarity

Question 18

What is ADH and how does it affect blood pressure and osmolarity?

Answer 18

• peptide hormone synthesized by the hypothalamus and release by the posterior pituitary
• its release is stimulated not only by low blood volume but also by high blood osmolarity
• its increases the permeability of the collecting duct to water, increasing water reabsorption
• this results in an increased blood volume (and pressure) and a decreased blood osmolarity

Question 19

How can the kidney regulate pH?

Answer 19

by selective reabsorption or secretion of bicarbonate or H ions

Question 20

What is the role of skin?

Answer 20

acts as a barrier protecting us from the elements and invasion of pathogens

Question 21

What are the 3 major layers of the skin?

Answer 21

hypodermis (subcutaneous layer), dermis, and epidermis

Question 22

What 5 layers compose the epidermis?

Answer 22

Come, Let’s Get Sun Burned

• stratum basale/spinosum/granulosum/lucidum/corneum
• stratum basale contains stem cells that proliferate to form keratinocytes
• keratinocyte nuclei are lost in the stratum granulosum, and many thin layers form the stratum corneum

Question 23

What do melanocytes produce?

Answer 23

melanin, which protects the skin from DNA damage caused by UV radiation; melanin is passed to keratinocytes

Question 24

What are langerhans cells?

Answer 24

special macrophages that serve as antigen-presenting cells in the skin

Question 25

What layers compose the dermis?

Answer 25

papillary (loose connective tissue) and reticular layer (dense connective tissue)

Question 26

What sensory cells are in the dermis?

Answer 26

• Merkel cells (deep pressure and texture)
• Ruffini endings (stretch)
• Pacinian corpuscles (deep pressure and vibration)

Question 27

What does the hypodermis contain and what does it connect?

Answer 27

fat and connective tissue and connects the skin to the rest of the body

Question 28

How does the skin use cooling mechanisms for thermoregulation?

Answer 28

• sweating, which draws heat from the body through evaporation of water from sweat, and vasodilation
• sweat glands are innervated by postganglionic cholinergic sympathetic neurons

Question 29

How does the skin using warming mechanisms for thermoregulation?

Answer 29

• piloerection, in which arrector pili muscles contract, causing hairs to stand on end (trapping a layer of warmed air around the skin);
• vasoconstriction
• shivering
• insulation provided by fat

Question 30

What can skin help prevent?

Answer 30

dehydration and salt loss from the body

Question 31

How does the glomerulus help in identifying health problem?

Answer 31

• small molecules dissolved in the blood will pass through the tiny pores (such as glucose, which is later reabsorbed)
• large molecules such as protein and blood cells will not pass through
• if blood cells or proteins are found in the urine, indicates a health problem at the level of the glomerulus

Question 32

What are the major waste products excreted in the urine?

Answer 32

Dump the HUNK

H+, Urea, NH3, K+

Question 33

List structures in the excretory pathway, from where filtrate enters the nephron to the excretion of urine from the body.

Answer 33

Bowman’s space > proximal convoluted tubule > descending limb of the loop of Henle > ascending limb of the loop of Henle > distal convoluted tubule > collecting duct > renal pelvis > ureter > bladder > urethra

Question 34

List the vessels in the renal vascular pathway, starting from the renal artery and ending at the renal vein.

Answer 34

renal artery > afferent arteriole > glomerulus > efferent arteriole > vasa recta > renal vein

Question 35

What is Bowman’s capsule?

Answer 35

the site of filtration, through which water, ions, amino acids, vitamins, and glucose pass (essentially everything besides cells and proteins)

Question 36

What are the predominant cell types in the epidermis?

Answer 36

keratinocytes

Question 37

Which segments of the nephron is sodium not actively transported out of the nephron?

Answer 37

• sodium is actively transported out of the nephron in the proximal and distal convoluted tubules, where the concentration of sodium outside the nephron is higher than inside, thus energy is required to transport sodium molecules against their concentration gradient
• in the inner medulla, however, sodium and other ions diffuse passively down their concentration gradients at the thin ascending limb of the loop of Henle

Question 38

Which region of the kidney has the lowest solute concentrations under normal physiological conditions?

Answer 38

• cortex, where the proximal convoluted tubule and a part of the DCT are found
• the solute concentration increases as one descends into the medulla and concentrated urine can be found in the renal pelvis

Question 39

What should be excreted in large quantities if the pH of the blood is too high?

Answer 39

bicarbonate ions