Biology: Chapter 10

Question 1

The excretory system

Answer 1

kidneys, ureters, bladder, and urethra

Question 2

Functional unit of the kidney

Answer 2

nephron

Question 3

Path of filtrate/urine

Answer 3

-nephron
-renal pelvis
-ureter
-bladder
-urethra

Question 4

Distinct areas of nephron tubule (in order)

Answer 4

-proximal convoluted tubule
-descending and ascending limbs of the loop of Henle
-distal convoluted tubule
-collecting duct

Question 5

Internal urethral sphincter

Answer 5

consists of smooth muscle (under involuntary control) and is contracted in its normal state

Question 6

External urethral sphincter

Answer 6

consists of skeletal muscle and is under voluntary control

Question 7

Osmoregulation

Answer 7

-The kidney filters the blood to form urine
-Primary job of the kidneys is to regulate blood volume and osmolarity
-Kidney function may be divided into three different processes in order to achieve this: filtration, secretion, and reabsorption

Question 8

Filtration (osmoregulation)

Answer 8

-About 20% of the blood that passes through the glomerulus is filtered as fluid into Bowman’s space; collected fluid is known as filtrate and movement is governed by Starling forces
-Hydrostatic pressure in the glomerulus is significantly higher than that in Bowman’s space which causes fluid to move into the nephron
-Osmolarity of blood is higher than that of Bowman’s space, resulting in pressure opposing the movement of fluid into the nephron
-Under most circumstances, fluid will flow from the glomerulus into Bowman’s space
-Movement of solutes from blood to filtrate at Bowman’s capsule

Question 9

Secretion (osmoregulation)

Answer 9

-Nephrons are also able to secrete salts, acids, bases, and urea directly into the tubule by either active or passive transport
-The kidneys are capable of eliminating ions or other substances when present in relative excess in the blood
-Secretion is also a mechanism for excreting wastes that are simply too large to pass through glomerular pores
-Movement of solutes from blood to filtrate anywhere besides Bowman’s capsule

Question 10

Reabsorption (osmoregulation)

Answer 10

-Some compounds that are filtered or secreted may be taken back up for use
-Examples include glucose, amino acids, and vitamins
-Movement of solutes from filtrate to blood

Question 11

Nephron function

Answer 11

-keep what they body needs and lose what it doesn’t, and concentrate the urine to conserve water
-Anything that makes it into the filtrate and that is not reabsorbed will be lost from the body in urine

Question 12

Proximal convoluted tubule (PCT)

Answer 12

-Filtrate first enters here
-Amino acids, glucose, water-soluble vitamins, and the majority of salts are reabsorbed along with water here
-Site of secretion for a number of waste products: hydrogen ions, potassium ions, ammonia, and urea; dump the HUNK (H+, Urea, NH3, K+)

Question 13

Loop of Henle

Answer 13

-Filtrate then enters the descending limb of the loop of Henle; dives deep into the medulla before turning around to become the ascending limb of the loop of Henle
-The vasa recta and nephron create a countercurrent multiplier system meaning that the flow of filtrate through the loop of Henle is in the opposite direction from the flow of blood through the vasa recta
-The loop of Henle becomes thicker because the cells lining the tube are larger in order to allow the reabsorption of sodium and chloride by active transport

Question 14

Descending limb (loop of Henle)

Answer 14

permeable only to water; as the descending limb travels deeper into the medulla, the increasing interstitial concentration favors the outflow of water from the descending limb, which is reabsorbed into the vasa recta

Question 15

Ascending limb (loop of Henle)

Answer 15

only permeable to salts and is impermeable to water

Question 16

Distal convoluted tubule (DCT)

Answer 16

-Responds to aldosterone, which promotes sodium reabsorption
-Water will follow the sodium, concentration the urine and decreasing its volume
-Anything that is not reabsorbed from the tubule by the end of the collecting duct will be excreted

Question 17

How blood pressure impacts the excretory system

Answer 17

-decreased blood pressure stimulates release of renin from juxtaglomerular cells in the kidney
-Renin cleaves angiotensinogen, a liver protein, to form angiotensin I. This peptide is metabolized by angiotensin-converting enzymes in the lungs to form angiotensin II, which promotes the release of aldosterone from the adrenal cortex
-Aldosterone alters the ability of DCT and collecting duct to reabsorb sodium and reabsorbing more sodium allows water to flow with it which increases blood volume and blood pressure
-ADH only governs water reabsorption and thus results in a lower blood osmolarity
-Aldosterone causes both salt and water reabsorption and doesn’t change blood osmolarity

Question 18

Epidermis

Answer 18

-the surface epithelium of the skin
-Subdivided into layers called strata
-From deepest layer outward: stratum basale, stratum spinosum, stratum granulosum, stratum lucidum, and stratum corneum

Question 19

Stratum Basale

Answer 19

-deepest layer (“the base”)
-contain stem cells and responsible for proliferation of keratinocytes, the predominant cells of the skin, that produce keratin

Question 20

Stratum spinosum

Answer 20

-gives epidermis its strength and holds cells tightly together to prevent tearing of the skin
-site of Langerhans cells
-just above stratum basale

Question 21

Stratum granulosum

Answer 21

-keratinocytes die and lose their nuclei
-just above stratum spinosum
-help to form waterproof barrier that functions to prevent fluid loss from the body

Question 22

Stratum lucidum

Answer 22

-only present in thick, hairless skin, such as the skin on the sole of the foot or palm of the hands, and is nearly transparent
-just above stratum granulosum when present

Question 23

Stratum corneum

Answer 23

-outermost layer of the epidermis (the surface)
-contains up to several dozen layers of flattened keratinocytes, forming a barrier that prevents invasion of pathogens and helps to prevent loss of fluids and salt

Question 24

Cells of the epidermis

Answer 24

-keratinocytes, melanocytes, and Langerhans cells

Question 25

Keratinocytes

Answer 25

-resistant to damage and provides protection against injury, water, and pathogens
-Calluses, fingernails, and hair are all formed from this

Question 26

Melanocytes

Answer 26

-found in stratum basale
-Produce melanin, a pigment that serves to protect the skin from DNA damage caused by ultraviolet radiation

Question 27

Langerhans cells

Answer 27

-special macrophages that reside within stratum spinosum
- Present antigens to T-cells in order to activate the immune system

Question 28

Dermis

Answer 28

-middle layer of skin
-Papillary layer: consists of loose connective tissue
-Reticular layer: below papillary layer and more dense
-Sweat glands, blood vessels, and hair follicles originate in the dermis
-Most sensory receptors are also located in dermis

Question 29

Merkel cells (dermis)

Answer 29

-sensory receptors present at the epidermal-dermal junction
-Responsible for deep pressure and texture sensation

Question 30

Meissner’s corpuscles

Answer 30

respond to light touch

Question 31

Ruffini endings

Answer 31

respond to stretch

Question 32

Pacinian corpuscles

Answer 32

respond to deep pressure and vibration

Question 33

Hypodermis

Answer 33

-deepest layer of skin
-Layer of connective tissue that connects the skin to the rest of the body
-Contains fat and fibrous tissue

Question 34

Thermoregulation

Answer 34

-Achieved by sweating, piloerection, vasodilation, and vasoconstriction
-Vasodilation occurs at the same time as sweating to maximize heat loss. Brings a large quantity of blood to the skin, which accelerates evaporation of sweat

Question 35

Sweating

Answer 35

-controlled by the autonomic nervous system
-Postganglionic sympathetic neurons that utilize acetylcholine innervate sweat glands and promote the secretion of water with certain ions onto the skin
-Heat is then absorbed from the body as the water molecules undergo a phase change to evaporate
-It is this evaporation of water that cools the skin

Question 36

Thermoregulation in cold conditions

Answer 36

-Arrector pili muscles contract, causing hairs to stand on end which helps trap a layer of heated air near the skin
-The arterioles that feed the capillaries of the skin constrict, limiting the quantity of blood reaching the skin
-Skeletal muscle may contract rapidly causing shivering; Shivering requires a sizable amount of ATP
-Layer of fat just below the skin also helps keep the body warm

Question 37

Skin and osmolarity

Answer 37

The skin is relatively impermeable to water which prevents not only the entrance of water through the skin but also the loss of water from the tissues