Chapter 10: Homeostasis

Question 1

The Excretory System

Answer 1

START

Question 2

The excretory system serves many functions, including the

Answer 2

regulation of blood pressure, blood osmolarity, acid–base balance, and removal of nitrogenous wastes.

Question 3

The kidney produces

Answer 3

urine, which flows into the ureter at the renal pelvis. Urine is then collected in the bladder until it is excreted through the urethra.

Question 4

The kidney contains a

Answer 4

cortex and a medulla.

Each kidney has a hilum, which contains a renal artery, renal vein, and ureter.

Question 5

The kidney contains a

Answer 5

portal system with t_wo capillary beds_ in series.

• Blood from the renal artery flows into afferent arterioles, which form glomeruli in Bowman’s capsule (the first capillary bed).
• Blood then flows through the efferent arteriole to the vasa recta (the second capillary bed), which surround the nephron, before leaving the kidney through the renal vein.

Question 6

Blood from the renal artery flows into

Answer 6

afferent arterioles, which form glomeruli in Bowman’s capsule (the first capillary bed).

Question 7

Blood then flows through the

Answer 7

efferent arteriole to the vasa recta (the second capillary bed), which surround the nephron, before leaving the kidney through the renal vein.

Question 8

The bladder has a muscular lining known as the

Answer 8

detrusor muscle, which is under parasympathetic control. It also has two muscular sphincters.

• The internal urethral sphincter consists of smooth muscle and is under involuntary (parasympathetic) control.
• The external urethral sphincter consists of skeletal muscle and is under voluntary control.

Question 9

The internal urethral sphincter consists of

Answer 9

smooth muscle and is under involuntary (parasympathetic) control.

Question 10

The external urethral sphincter consists of

Answer 10

skeletal muscle and is under voluntary control.

Question 11

The ___ consists of smooth muscle and is under involuntary (parasympathetic) control.

Answer 11

internal urethral sphincter

Question 12

The ___ consists of skeletal muscle and is under voluntary control.

Answer 12

external urethral sphincter

Question 13

The kidney participates in solute movement through three processes:

Answer 13

Filtration,

Secretin, and

reabsorption

• Filtration is the movement of solutes from blood to filtrate at Bowman’s capsule. The direction and rate of filtration is determined by Starling forces, which account for the hydrostatic and oncotic pressure differentials between the glomerulus and Bowman’s space.
• Secretion is the movement of solutes from blood to filtrate anywhere other than Bowman’s capsule.
• Reabsorption is the movement of solutes from filtrate to blood.

Question 14

Filtration is the movement of

Answer 14

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

Question 15

Secretion is the movement of

Answer 15

solutes from blood to filtrate anywhere other than Bowman’s capsule.

Question 16

Reabsorption is the movement of

Answer 16

solutes from filtrate to blood.

*Filtrate –> blood

Question 17

Each segment of the nephron has a specific function:

Answer 17

• The proximal convoluted tubule (PCT) is the site of bulk reabsorption of glucose, amino acids, soluble vitamins, salt, and water. It is also the site of secretion for hydrogen ions, potassium ions, ammonia, and urea.
• The descending limb of the loop of Henle is 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.

permeable to water meaning:That allows water to permeate through its structure.

• The ascending limb of the loop of Henle is permeable to salt but not water; therefore, salt is reabsorbed both passively and actively. The diluting segment is in the outer medulla; because salt is actively reabsorbed in this site, the filtrate actually becomes hypotonic compared to the blood.
• The distal convoluted tubule (DCT) is responsive to aldosterone and is a site of salt reabsorption and waste product excretion, like the PCT.
• The collecting duct is responsive to both aldosterone and antidiuretic hormone and has variable permeability, which allows reabsorption of the right amount of water depending on the body’s needs.

Question 18

The proximal convoluted tubule (PCT) is the site of

Answer 18

bulk reabsorption of glucose, amino acids AA, soluble vitamins, salt, and water.

It is also the site of secretion for hydrogen ions, potassium ions, ammonia, and urea.

Question 19

The descending limb of the loop of Henle is

Answer 19

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 20

The ascending limb of the loop of Henle is

Answer 20

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

Question 21

The distal convoluted tubule (DCT) is

Answer 21

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

Question 22

The collecting duct is

Answer 22

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

Question 23

The kidney is under ___.

When blood pressure (and volume) are low, two different hormonal systems are activated.

Answer 23

hormonal control!!

• Aldosterone is a steroid hormone regulated by the renin–angiotensin–aldosterone system that increases sodium reabsorption in the distal convoluted tubule and collecting duct, thereby increasing water reabsorption. This results in an increased blood volume (and pressure), but no change in blood osmolarity.
• Antidiuretic hormone (ADH or vasopressin) is a peptide hormone synthesized by the hypothalamus and released by the posterior pituitary. Its release is stimulated not only by low blood volume but also by high blood osmolarity. It 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 24

Aldosterone is a

Answer 24

steroid hormone regulated by the renin–angiotensin–aldosterone system that increases sodium reabsorption in the distal convoluted tubule and collecting duct, thereby increasing water reabsorption. This results in an increased blood volume (and pressure), but no change in blood osmolarity.

Question 25

Antidiuretic hormone (ADH or vasopressin) is a

Answer 25

peptide hormone synthesized by the hypothalamus and released by the posterior pituitary. Its release is stimulated not only by low blood volume but also by high blood osmolarity. It 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 26

The kidney can regulate pH by

Answer 26

selective reabsorption or secretion of bicarbonate or hydrogen ions.

Question 27

Skin

Answer 27

START

Question 28

The skin acts as a

Answer 28

barrier, protecting us from the elements and invasion by pathogens.

Question 29

The skin is composed of three major layers:

Answer 29

Epidermis

Dermis

The hypodermis (subcutaneous layer)

Question 30

The epidermis is composed of five layers:

Answer 30

the stratum basale, stratum spinosum, stratum granulosum, stratum lucidum, and stratum corneum.

The stratum basale contains stem cells that proliferate to form keratinocytes. Keratinocyte nuclei are lost in the stratum granulosum, and many thin layers form in the stratum corneum.

Question 31

Melanocytes produce

Answer 31

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

Question 32

Langerhans cells are

Answer 32

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

Question 33

The dermis is composed of two layers:

Answer 33

1. Papillary layer
2. The reticular layer

Question 34

Many sensory cells are located in the

Answer 34

dermis, including Merkel cells (deep pressure and texture), free nerve endings (pain), Meissner’s corpuscles (light touch), Ruffini endings (stretch), and Pacinian corpuscles (deep pressure and vibration).

Question 35

The hypodermis contains

Answer 35

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

Question 36

The skin is important for

Answer 36

thermoregulation, or the maintenance of a constant internal temperature.

• Cooling mechanisms include sweating, which draws heat from the body through evaporation of water from sweat, and vasodilation. Sweat glands are innervated by postganglionic cholinergic sympathetic neurons.
• Warming mechanisms include: piloerection, in which arrector pili muscles contract, causing hairs to stand on end (trapping a layer of warmed air around the skin); vasoconstriction; shivering; and insulation provided by fat.

Question 37

Cooling mechanisms include

Answer 37

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 38

Warming mechanisms include:

Answer 38

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

Question 39

The skin also prevents

Answer 39

dehydration and salt loss from the body.

Question 40

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

Answer 40

1. 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 41

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

Answer 41

2. Renal artery → afferent arteriole → glomerulus → efferent arteriole → vasa recta → renal vein

Question 42

3� What arm of the nervous system is responsible for contraction of the detrusor muscle?

Answer 42

3. The parasympathetic nervous system causes contraction of the detrusor muscle.

Question 43

4� What are the three processes by which solutes are exchanged between the filtrate and the blood? What happens in each process?

• • •

Answer 43

4. Filtration is the movement of solutes from blood into filtrate at Bowman’s capsule. Secretion is the movement of solutes from blood into filtrate anywhere besides Bowman’s capsule. Reabsorption is the movement of solutes from fil-trate into blood.

Question 44

5� For each segment of the nephron listed below, what are its major functions?

• Bowman’s capsule:
• Proximal convoluted tubule:
• Descending limb of the loop of Henle:
• Ascending limb of the loop of Henle:
• Distal convoluted tubule:
• Collecting duct:

Answer 44

5. Bowman’s capsule is the site of filtration, through which water, ions, amino acids, vitamins, and glucose pass (essentially everything besides cells and proteins).

The proximal convoluted tubule controls solute identity, reabsorbing vitamins, amino acids, and glucose, while secreting potassium and hydrogen ions, ammonia, and urea.

The descending limb of the loop of Henle is import-ant for water reabsorption, and uses the medullary concentration gradient.

The ascending limb of the loop of Henle is important for salt reabsorption and dilu-tion of the urine in the diluting segment.

The distal convoluted tubule, like the PCT, is important for solute identity by reabsorbing salts while secreting potas-sium and hydrogen ions, ammonia, and urea.

The collecting duct is important for urine concentration; its variable permeability allows water to be reabsorbed based on the needs of the body.

Question 45

1� What is the predominant cell type in the epidermis?

Answer 45

1. Keratinocytes are the primary cells of the epidermis.

Question 46

2� What are the layers of the epidermis, from superficial to deep?

• • • • •

Answer 46

2. Stratum corneum, stratum lucidum, stratum granulosum, stratum spinosum, stratum basale

Question 47

3� What are the layers of the dermis, from superficial to deep?

• •

Answer 47

3. The papillary layer and the reticular layer

Question 48

4� What are some mechanisms the body uses to cool itself? What are some mechanisms the body uses to retain heat?

• Cooling: • Retaining heat:

Answer 48

4. The body can cool itself through sweating and vasodilation. The body can warm itself through vasoconstriction, piloerection, and shivering.