SImple concepts that I keep getting confused

[MrE2u]

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There are a few simple concepts that I can't quite keep straight in my head and I'm hoping the SDN can help me out here.

The first one is hydrostatic vs osmotic pressures when talking about capillaries. I know osmotic pressure is a characteristic of solution concentration and hydrostatic pressure if a fluid characteristic, but I can't visualize the way they affect capillaries. (I can try to dig up the sample question if I need to, for reference)

The other thing I can't keep straight is the process of reabsorption in the kidney. I never took any A&P classes so I'm really just learning it for the first time, but I see a lot of questions talking about Calcitonin, ADH, and PTH. I have a vague idea what they do from reading the wikipedia pages on each of them, but does reabsorption in the tubules put things back into the blood or does it send them to the bladder for expulsion?

 

[Czarcasm]

There are a few simple concepts that I can't quite keep straight in my head and I'm hoping the SDN can help me out here.

The first one is hydrostatic vs osmotic pressures when talking about capillaries. I know osmotic pressure is a characteristic of solution concentration and hydrostatic pressure if a fluid characteristic, but I can't visualize the way they affect capillaries. (I can try to dig up the sample question if I need to, for reference)

The other thing I can't keep straight is the process of reabsorption in the kidney. I never took any A&P classes so I'm really just learning it for the first time, but I see a lot of questions talking about Calcitonin, ADH, and PTH. I have a vague idea what they do from reading the wikipedia pages on each of them, but does reabsorption in the tubules put things back into the blood or does it send them to the bladder for expulsion?

Osmotic pressure is the pressure developed by solutes dissolved in water working across a selectively permeable membrane. It is generated by all the dissolved solutes - salts, nutrients, proteins - all dissolved solutes.

Oncotic pressure is Colloid Osmotic Pressure - the part of the osmotic pressure created by the larger colloidal solute components. A colloid is where larger particles are suspended in water but they are small enough or have features that prevent them from settling out, distinguishing it from a suspension). Albumin (protein made by the liver and released into blood) is a colloidal protein that generates osmotic pressure and is the plasma component that generates most of the Colloidal Osmotic Pressure or Oncotic Pressure of blood, and has the effect of drawing much of the water back into the blood from the tissues at the venous end of capillary beds. Without enough albumin in blood , the fluid that is forced into the tissues by Blood pressure (Hydrostatic pressure) at the arterial end of the capillaries would not be sufficiently drawn back into the blood, the tissues become waterlogged and a condition known as edema develops. In severe cases in liver disease or nutritional protein deficiency results in very low blood albumin levels, the excess fluid drains into body cavities and is responsible for the "pot bellies" seen in starving kids in Africa.

 

[Czarcasm]

There are a few simple concepts that I can't quite keep straight in my head and I'm hoping the SDN can help me out here.

The first one is hydrostatic vs osmotic pressures when talking about capillaries. I know osmotic pressure is a characteristic of solution concentration and hydrostatic pressure if a fluid characteristic, but I can't visualize the way they affect capillaries. (I can try to dig up the sample question if I need to, for reference)

The other thing I can't keep straight is the process of reabsorption in the kidney. I never took any A&P classes so I'm really just learning it for the first time, but I see a lot of questions talking about Calcitonin, ADH, and PTH. I have a vague idea what they do from reading the wikipedia pages on each of them, but does reabsorption in the tubules put things back into the blood or does it send them to the bladder for expulsion?

http://www.youtube.com/results?search_query=khan+academy+kidney

 

[gettheleadout]

The other thing I can't keep straight is the process of reabsorption in the kidney. I never took any A&P classes so I'm really just learning it for the first time, but I see a lot of questions talking about Calcitonin, ADH, and PTH. I have a vague idea what they do from reading the wikipedia pages on each of them, but does reabsorption in the tubules put things back into the blood or does it send them to the bladder for expulsion?

Simple answer for this is secretion = spitting stuff out into the filtrate, while reabsorption = sucking stuff back in from the filtrate. The filtrate eventually becomes the urine, so you want to secrete wastes or things you don't want and reabsorb things you need to keep. Modulation of these activities primarily occurs in the distal convoluted tubule and collecting duct (that's where those hormones act).