The kidneys structure, functions, and what controls these functions Essay Example for Free

The kidneys structure, functions, and what controls these functions Essay The kidney is made up of nephrons, which are a kidneys functional units. These nephrons collect fluid filtered from the blood. The kidney connects to the renal artery, renal, vein, and ureter. Purified blood leaves the kidney using the renal vein, urine leaves using a ureter and the renal artery carries blood from the aorta to the kidney. The nephron has a cup-shaped nephric capsule that surrounds a cluster of capillaries called the glomerulus. A good deal of fluid from the blood filters into the capsule. Large proteins and whole blood cells are left behind due to the fact that their too big to pass through the filters along with the plasma or blood fluid. There are four main parts of the nephron tubule: the proximal convoluted tubule, the U-shaped loop of Henle, the distal convoluted tubule, and the collecting duct. A substantial amount of resorption takes place in the proximal convoluted tubule. The small proteins, glucose, and ions are returned to the blood by active transport. If the glucose in the filtrate, or filtered fluid, exceeds the kidney threshold level, some glucose will remain and appear in the urine. The loops of Henle permit the production of rather concentrated urine. The collecting duct, together with the loop of the Henle, plays a vital role in water balance. The concentration of urine takes place in the collecting ducts although the process depends on the activities in the loops of Henle. The loops of Henle and the collecting ducts are in the medulla of the kidney. The other parts of the nephron are outside the medulla in the outer region, the cortex. Theres a fluid in the medulla that contains an osmotic gradient in which solutes are steadily more concentrated in the direction away from the cortex. There are two kinds of solutes in the gradient: salt and urea. The loops of Henle create a salt gradient which actively transport salt ions out of the filtrate. The actual concentration of the urine takes place in the collecting duct after the urine passes through the distal convoluted tubule from the loop of Henle. The urine leaves the collecting duct through the pelvis of the kidney  and down the ureter to the urinary bladder. Urine composition and rate of urine formation is regulated by the hormones vasopressin, aldosterone, and angiotensin, and the enzyme renin. The posterior pituitary gland in the brain releases vasopressin. Vasopressin increases resorption of water from the urine. When the body is losing water the body stimulates vasopressin secretion in result slowing down the loss of water through urine. The body detects water decrease either by lower blood volume (i.e. bleeding) or an increase in concentration of blood plasma (i.e. sweating). Very little water is resorbed from urine when there is an absence of vasopressin. Water volume depends on the amount of salt; therefore the amount of salt in the body directly affects the volume and concentration of the blood. When the salt levels in the blood increase the adrenal gland in the kidney secretes a hormone called aldosterone. Aldosterone causes the body to resorb sodium by the distal tubule. The rate is determined by blood salt content. Since less salt is resorbed by the kidney the urines salt content increases therefore increasing urinary volume. When the sodium levels in the blood decrease the kidneys secrete and enzyme called renin. Renin converts the plasma protein angiotensinogen into the hormone angiotensin. Angiotensin causes the constriction of blood vessels to increase the aldosterone secretion. Then the aldosterone promotes the resorption of sodium by the kidney and the urines salt content decreasing urinary volume.

Lord Of The Flies: Summary :: essays research papers

Lord of the Flies: Summary By: Wiliam Golding Main Character Description Piggy: A large kid, one of the older ones. He was made fun of and teased about his weight and it drove him crazy. He met Ralph first. Piggy wore glasses, which later proved vital for fire making. The best way to get to Piggy was to take away his â€Å"specs† because without them, he couldn't see a foot away from anything. He is later killed in the book. He falls fourty feet onto solid rock and his head splits open. Ralph: Ralph is chief of the group on the very first day. He was voted above Jack and his small band of kids. Ralph is one of the oldest. He first meets Piggy and was the original founder of the Conch Horn. Ralph comes up with many useful ideas during the novel, like the shelters on the beach. He is hunted right before they are rescued. Jack: Has his own band of kids that he later names, his â€Å"hunters.† In the group, they are responsible for the hunting of the pigs of the island; to bring in meat. Otherwise, the only thing they had to eat was the fruit of the island. Later on in the novel, Jack leaves the group of kids to be on his own. Simon: Quiet, out-spoken by everyone, Simon is one of the hardest-working of them all. He helps Ralph with the shelters and the little ones with fruit. He is later killed in the novel. Sam ‘n Eric: Sam and Eric are twins. They help in various problems during the novel and survive until the end of the novel. Neither of them play a vital role in the novel. Chapter Summary Chapter 1- In the first chapter, the time is right after the plane has wrecked and they all wake up from the crash. Ralph and Piggy meet each other, walk around and soon look for other people on the plane. Ralph soon finds the Conch shell and uses it like a horn to beacon the others. The survivors eventualy find themselves together in a group; Ralph, Piggy, Jack and his hunters, Sam ‘n Eric and Simon included. They vote Ralph the chief of the group, make a few rules (like, whoever has the Conch Shell has the right to speak) and designate Jack and his band as the group's â€Å"hunters.† Ralph, Simon and Jack explore the island and climb it's pink mountain to see if the place they were at is trully an island. They find it is. Chapter 2- An idea is formed for the group.

Innocence of Youth Essay

In The Catcher in the Rye, J.D. Salinger shows how an adolescent boy develops a cynical outlook on life, causing him to feel isolated. Salinger uses Holden to interpret change from the innocence of youth to the responsibilities of adulthood. Holden’s confusion represents that difficult change a person experiences while growing up. He is trying to find his place in the world, but certain obstacles are preventing him from moving forward. The path to redemption is difficult for him because he doesn’t want to accept the responsibilities of being an adult. The novel shows that through adolescence a person faces many new changes that can be difficult to accept. Holden wants the preserve the innocence that a person has as a child. His cynical views of the world develop through his experience with the corruption of the adolescent world. â€Å"Certain things, they should stay the same. You ought to be able to stick them in one of those big glass cases and just leave them alone, I know that’s impossible but it’s too bad anyway.†(Salinger 122) Salinger points out that, changes are not always positive and it would be easier if we could preserve some things. Holden doesn’t want to face the reality of adulthood because he hasn’t experienced many events that show the positive side of being an adult. Holden’s search for moral values is a difficult and lonely path because of his minimal success of finding them. â€Å"Holden speaks of his loneliness and depression; the story of a few days in his life indicates how sad and lonely his search for moral values is in which he finds them to be sorely lacking.†(Walters 3) The search for innocence and moral is often times very lonely due to the constant heinous events that occur. Characters like Holden want to realize a better life that is away from the corruption of civilization. (Walters 3) Throughout his life, Holden experienced many events that show the corruption of adults and teens. He believes that as a person grows up, they fall into a pit of evil and cruelty. He dreams of becoming the catcher in the rye and saving children from falling into the tainted world of adults. Salinger interprets children as pure and free of sins. Purity is often associated with kids as they have not experienced the greed and desires of adul ts. The thing Holden holds closest to him is the memory of his unique brother Allie. The qualities Allie possesses are extremely unique among even kids, which is why Holden is so mesmerized with him. He was not able to experience the adolescence of Allie, which could have contributed to his obsession with innocence. â€Å"Holden’s fantasy elaborates his obsession with innocence and his perhaps surprisingly traditional moral code.†(Walters 3) Holden’s moral code is different because he is often rude, lies to people and even pursues sexual intercourse. Although his moral code is different, he still has the right intentions. His lies are often to make people feel better and his rude attitude is a result of his distaste for immorality. Holden is confused and doesn’t know how to face the world or the people in it. The time period and environment in the novel are aspects that could have contributed to the confusion. Holden’s experienced this confusion during a time of tension in the United States. The post World War II time period could have had negative effects on Holden through conformism and dramatic changes occurrence in the U.S. â€Å"Holden experiences both the confusion of adolescence and spiritual discomfort of an entire age.†(Historical 6) Holden experiences events in New York City, a city of demoralization, crime and crookedness. His cynical perception of the cruel world could have been limited to the setting of the novel. Prep school and public schools are both socially and economically different than public schools. (Historical 8) His time at school could have influenced his emotion due to the elevated expectations of prep schools. There are many aspects of Holden’s life that could have contributed to his confusion and hatred. Confusion is a common emotion during the adolescent stage of a person life. Holden’s confusion is a result of his inability to truly connect with anyone because of his cynical views. He has a feeling of hopelessness for the world around him because of his distaste for adulthood. â€Å"Holden tells the story of his disenchantment with his life and the direction it is taking.†(Walters 2) The realization that he will be entering adulthood evntually depresses him. He wants to retreat backward into the world he is leaving, that of childhood innocence. (Vanderbilt 298) Holden wears a red hat is symbolic of his position in life and the direction it is taking. Wearing it backwards suggests not only his defiant withdrawal from teammates but his desire to go back to his youth. (Vanderbilt 297). Holden finally decides he needs to move on in life after meeting with his sister Phoebe. The innocence of his younger sister allows him to truly find what he is looking for. Through his sister, he finds hope for the world around him. It is through the innocence of Phoebe, at the end, that Holden initially moves toward his redemption. (Vanderbilt 299) Holden’s cloudy stage of confusion eventually starts to clear up. His realization that his actions affect that people he cares about allows him to seek redemption. He states that he will start applying himself in school and has a better outlook on life. Work Cited Page Literary and Historical Context.† The Catcher in the Rye: Innocence Under Pressure. Sanford Pinsker. New York: Twayne Publishers, 1993. [1]. Twayne’s Masterwork Studies 114. Gale Virtual Reference Library. Web. 27 Feb. 2013. Salinger, J D. The Catcher in the Rye. Boston: Little, Brown, 1951. Print. Vanderbilt, Kermit. â€Å"Symbolic Resolution In The Catcher In The Rye: The Cap, The Carrousel, And The American West.† Critical Insights: The Catcher In The Rye (2011): 297-305. Literary Reference Center. Web. 22 Feb. 2013. Walters, Gordon. â€Å"The Catcher In The Rye.† Masterplots, Fourth Edition (2010): 1-2. Literary Reference Center. Web. 22 Feb. 2013.

Definition and Examples of Present Perfect Progressive