Chapter 10: Homeostasis Flashcards
Detrusor muscle
Muscular lining of the bladder
Internal urethral sphincter
Consists of smooth muscle and is contracted in its normal state
External urethral sphincter
Consists of skeletal muscle and is under voluntary control
Micturition reflex
When the bladder is full, stretch receptors convey to the nervous system that the bladder requires emptying; parasympathetic neurons fire; detrusor muscle contracts which causes internal sphincter to relax
Proximal Convoluted Tubule
Amino acids, glucose, water-soluble vitamins, and the majority of salts are reabsorbed along with water; almost 70% of filtered sodium will be reabsorbed here; filtrate remains isotonic to the interstitium as other solutes and large amounts of water are reabsorbed; site for secretion of hydrogen ions, urea, ammonia, and potassium ions
Loop of Henle
Descending limb of the loop of Henle - permeable only to water
Ascending limb of the loop of Henle - only permeable to salts (Na+, Cl-) and impermeable to water
Diluting segment
At the transition from the inner to outer medulla; cells lining the tube are larger and contain large amounts of mitochondria which allow the reabsorption of sodium and chloride by active transport; only region of the nephron that can produce urine more dilute than blood; by the end of the loop of Henle, filtrate is more dilute and the volume has greatly decreased
Distal convoluted tubule
Responds to aldosterone; site of waste produce secretion (active secretion of H+, K+, urea)
Collecting duct
The final concentration of the urine depends largely on the permeability of the CD; responsive to both ADH and aldosterone; anything that does not leave the tubule by the end of the collecting duct will be excreted
What does urine mostly contain?
Urea, uric acid, and excess ions (sodium, potassium, magnesium, and calcium)
Oncotic pressure
Osmotic pressure that is attributable to dissolved protein specifically
What is blood osmolarity usually maintained at?
290 mOsm
Bicarbonate buffer system
The major regulator of blood pH
How do the kidneys contribute to pH derangement
The kidneys are able to selectively increase or decrease the secretion of both hydrogen ions and bicarbonate; slower than the respiratory response
What is the structure of the skin?
Hypodermis (subcutaneous layer), dermis, and epidermis
Epidermis
Subdivided into strata
What is the deepest stratum to shallowest?
Stratum basale, stratum spinosum, stratum granulosum, stratum lucidum, stratum corneum
Stratum basale
Contains stem cells and is responsible for proliferation of keratinocytes - predominant skin cells that produce keratin
Stratum spinosum
Cells become connected to each other; site of Langerhans cells
Stratum granulosum
Keratinocytes die and lose their nuclei
Stratum lucidum
Only present in thick hairless skin, such as skin on the soles of the foot or the palms; nearly transparent
Stratum corneum
Contains up to several dozen layers of flattened keratinocytes, forming a barrier that prevents pathogen invasion and helps to prevent the loss of fluids and salt; hair projects above the skin and there are openings for sweat and sebaceous glands
Keratin
Resistant to damage and provides protection against injury, water, and pathogens
Calluses
Form from excessive keratin deposition in areas of repeated strain due to friction
Melanocytes
Derived from neural crest cells and found in the stratum basale; produce melanin - a pigment that serves to protect the skin from DNA damage caused by UV radiation
Langerhans cells
Special macrophages that reside within the stratum spinosum; capable of presenting antigens to T cells
Dermis
Upper layer (right below the epidermis) is the papillary layer - consists of loose connective tissue; lower layer is the denser reticular layer; sweat glands, blood vessels and hair follicles originate in the dermis
Merkel cells (discs)
Sensory cells present at the epidermal-dermal junction; connected to sensory neurons; deep pressure and texture sensation
Free nerve endings
Respond to pain
Meissner’s corpuscles
Light touch
Pacinian corpuscles
Deep pressure and vibraion
Ruffini endings
Stretch
Hypodermis
Connects the skin to the rest of the body; layer of connective tissue
Sweating
Cooling mechanism that is controlled by the sympathetic nervous system; postganglionic sympathetic neurons release ACh to promote the secretion of water with certain ions onto the skin
Arrector pili
These muscle contract resulting in piloerection; this helps to trap a layer of heated air near the skin; arterioles that feed the capillaries of the skin constrict, limiting the quantity of blood reaching the skin
Shivering
Requires a sizeable amount of ATP; significant portion of this ATP is lost as heat
White fat
Insulates the body
Brown fat
Much less efficient ETC therefore more heat energy is released as fuel is burned
