THE EXCRETORY SYSTEM

The Excretory System



The Excretory System

Introduction

Secretory or excretory system in biology - a set of bodies that bring the body of excess water, metabolic products, salts, and toxic substances introduced into the body from outside or formed within it.

In protists soluble excretions are displayed in the environment by diffusion or by using contractile vacuoles , functioning as osmoregulation . Separation from the cytoplasm of the liquid is released into spongiome - a complex system of membrane vesicles or channels.

A number of lower metazoan metabolic products diffuse through the surface of the body wall and cavities associated with the environment. Moreover, in cells of freshwater sponges and hydras are present vacuoles, which are involved in the accumulation and removal of excreta.

In most multicellular there are special organs of excretion - protonephridia , metanefridii , tselomodukty , nefromiksii , kidneys - that enable excretion from the body of harmful products of metabolism.

Bodies of allocation also include so-called "Kidneys of accumulation - the cells or tissues that accumulate harmful substances, usually translating them into an insoluble form.

In the selection functions may also participate in individual cells (eg phagocytes ), which can leave the body and organs of other systems (lungs, skin, etc.).

Discussion and analysis

The Cortex and Medulla

The definition of cortex and medulla is not uniform for all authors. Some use a purely anatomical definition in which the cortex is the peripheral region of the kidney and the medulla the central region, and this irrespective of their histological structure. Other authors, restrict the cortical region in renal parenchyma, which contains the Malpighian corpuscles. The medullary region is then represented by the pyramids and the pyramids of Malpighi Ferrein. Insofar as this course focuses on the histology, we chose a more histologically.

The medulla, located deep, is formed by the pyramids of Malpighi, the number of pyramids of Malpighi is variable and ranges between 8 and 18 according to Bloom and Fawcett (1975), so that a more precise number, it is important about an order of magnitude. Each has a top screened by Channel ports papillary protruding into the cavity of the calyx and a corresponding base, bristling with numerous small slender pyramids pointing convexity kidney Ferrein named pyramids.

The cortex, corresponding to the remaining renal parenchyma, is located in the periphery and between the pyramids of Malpighi

Proximal and Distal Convoluted Tubules

Are structural and functional units of the kidney. Leakage occurs in the nephrons. Its embryonic ...