Water, small molecules, and ions are forced through the glomerular capillaries into Bowman’s capsule in the process of filtration, largely due to the high blood pressure in the capillaries of the glomerulus. Nitrogenous compounds, namely urea, are filtered into Bowman's capsule for excretion. Glucose is also filtered into the capsule, but is reabsorbed in the proximal convoluted tubule; the presence of glucose in the final filtrate or urine can be indicative of diabetes or other maladies.

The correct answer is that two answer options are correct: small ions, glucose, amino acids, water, and nitrogenous compounds are all found in the initial filtrate.

Large molecules and cells are never filtered through the podocytes (cells lining the capsule), so we never expect to find blood cells or large blood proteins like albumin in the filtrate.

The nephrons are the basic filtration units of the kidneys. In the cortex (plural "cortices") or outer portion of the kidney, blood enters a nephron consisting of a glomerulus (mass of capillaries), renal tubules and loop of Henle. Urine is formed by filtration in the glomerulus and reabsorption and secretion in the tubules. The inner medulla of the kidney contains the collecting ducts, which merge together to form papillary ducts that enter into a calyx (plural "calyces") or funnel-shaped structure. The hilum is the part where the renal artery enters and renal vein and ureter leave the kidney.

The correct answer is antidiuretic hormone (ADH), also known as vasopressin. ADH controls the permeability of the collecting duct of the nephron to water. If ADH levels are high in the blood, more water will be reabsorbed into the bloodstream, concentrating the urine. Alternatively, if ADH levels are low, less water is reabsorbed into the bloodstream, and the urine is dilute. 

The large intestine is responsible for further absorption of water and any remaining nutrients that the small intestine did not absorb. Also, the large intestine is responsible for the formation of fecal matter.

The question states that the organ stores urine. Recall that bladder stores urine until excretion; therefore, the researcher must be analyzing a bladder. Smooth muscle and skeletal muscle are both muscle types found in the human body. Smooth muscle is involuntary, whereas skeletal muscle is voluntary. Recall that the muscle surrounding the bladder functions to empty the bladder. We cannot control bladder emptying; therefore, the muscle surrounding the bladder is involuntary and is classified as smooth muscle.

The excretory system for urine consists of the following components: kidneys, ureter, bladder, and urethra. These components are the same in both males and females. The urine is made in the kidneys. It exits the kidneys and travels through the ureter, bladder, and urethra, after which it is excreted.

The uterus is only found in females and the prostate is only found in males; however, these are reproductive structures and are not part of the excretory system. Age does not determine the structures of the excretory system. A teenager and an eighty-year old will have the same excretory system.

Kidneys are bilateral organs that function to filter metabolic waste products from the blood. These waste products are processed and excreted via urine. Once it is formed in the kidneys, urine exits via the ureter. The ureter carries the urine to the bladder, where it is stored until it can be excreted. Once the bladder is full, smooth muscles surrounding the bladder contract and push urine out of the bladder and into the urethra. The urethra is the last stop for urine, after which it is excreted.

The excretory system functions to remove waste from the body. This can happen via two pathways. First, kidneys filter metabolic wastes from the blood and excrete them via urine. Second, organs of the GI tract (such as the liver, small intestine, and colon) filter toxic substances and waste products from food and excrete it via feces; therefore, the excretory system functions to remove waste via urine and feces.

Another main function of the excretory system is to maintain homeostasis. To maintain homeostasis, the kidneys have the ability to sense changes in certain substances in the blood and can excrete them accordingly. For example, if there is an increase in the concentration of bicarbonate ions in the blood, the kidneys will sense this change and increase the excretion of bicarbonate ions via urine. This will bring the concentration of bicarbonate ions back to normal and will maintain homeostasis.

The word "renal" refers to the kidneys. Since it plays a huge role in excretion, kidney failure can alter excretory system functions.

Transitional epithelium consists of multiple layers of epithelial cells which can contract and expand. When the cells are not stretched they appear cuboidal with a domed apex, however once stretched the the tissue compresses and the cells appear flattened. This type of tissue is found in the urinary bladder, the ureters, the superior urethra, and gland ducts of the prostrate.  

All of these are functions of the kidney except for excretion of proteins. In fact, the kidney should never secrete protein or glucose (sugars) unless there is a disease state present. For example, in diabetics who have damaged kidneys (diabetic nephropathy), there is protein in the urine. To a degree, the amount of protein in the urine determines how bad their kidney disease is.