The Human Body (part 2)

Sistem Pencernaan Sistem pencernaan mengambil sari pati dari makanan dan cairan, kemudian memprosesnya sehingga dapat diserap ke dalam tubuh. Organ yang dibutuhkan untuk memproses sari pati tersebut secara kimiawi, yaitu : hati, kandung empedu, kelenjar ludah dan pankreas, selain lambung dan saluran pencernaan. Sistem pencernaan meliputi mulut, kerongkongan, lambung, usus kecil dan usus besar. Pencernaan makanan adalah proses penghancuran, pencairan dan pengolahan bahan makanan secara kimia sehingga sari pati tersebut dapat dimanfaatkan oleh tubuh. Proses pencernaan dimulai dari mulut, dimana gigi dan rahang secara mekanis menghancurkan makanan serta air liur menghancurkan secara kimiawi. Baik pencampuran secara mekanik maupun penghancuran secara kimiawi terjadi juga di dalam perut. Getah lambung bercampur dengan makanan membentuk pasta seperti susu yang disebut chyme. Kontraksi yang disebut gerakan peristaltik dalam perut mencampur bahan makanan bersama dengan chyme yang terjadi kira-kira setiap 20 detik. Setiap kontraksi menghasilkan beberapa mililiter isi perut yang masuk ke dalam usus. Nutrisi dan cairan diserap oleh tubuh dari chyime saat melewati usus. Chyme tersebut didorong dengan kecepatan sekitar 1 cm/menit oleh gerakan peristaltik di dalam usus. Limbah produksi dan sisa makanan yang tidak bermanfaat dikeluarkan dari tubuh melalui anus. Sistem Syaraf Sistem syaraf sangat penting fungsinya bagi makhluk hidup, khususnya manusia. Sebab sistem syaraflah yang mengatur sistem kontrol secara otomatis, terintegrasi dan mengasimilasi data dari dunia luar dengan organ-organ internal kita, kemudian mengatur dan mengontrol sistem gerak. Sistem ini seperti sebuah komputer yang sangat canggih dengan sistem komunikasi secara elektrik. Sistem syaraf yang otonom bertanggungjawab untuk mengatur fungsi otomatis dalam tubuh, yaitu detak jantung, kelenjar tubuh, sistem pencernaan dan sebagainya. Sistem syaraf otonom bekerja dengan sendirinya tanpa disadari.

The Human Body (part 1)

The Cell All mammals, including humans, are made up of basic building blocks called cell. Although many different types of cells are known, they differ according to function, they are all similar in their basic constituents. The different types of cell perform different jobs, so have different gross structures. The size of cells also varies, ranging from 200 nanometers to several centimeters in length. Most cells, however, fall within the range of 0.5 to 20 micrometers. The cell contains material used in chemical reactions that keep the cell functioning. It is surrounded by a semipermeable membrane. This membrane not only contains the cell material but also allows selective passage of metrials in and out of the cell. There may also be membrane structures inside of the cell that compartmentalized the various chemical reaction taking place. The structure of most cells includes a nucleus inside of the cell, separated from the surrounding cytoplasm by its own membrane. The nulceus contains the genetic coding or reproducible cells. Cells in the human body are quite numerous. It has been estimated that are approximately 75 trillion cells in the body, of which one-third (25 trillion) are red blood cells. The red blood cells are responsible for transporting oxygen to body tissues. Body Fluids The body is almost two-third fluid (actually, approximately 56 percent). Intracellular fluid contains large concentrations of potassium (K/Kalium), magnesium (Mg), and phosphat ion (PO4), while the extracellular fluid contains significant concentrations of sodium (Na/natrium), chloride (Cl), bicarbonat ions (HCO3), oxygen (O2), amino acids, glucose (CH12O6), and carbon dioxide (CO2). Musculoskeletal System The muscles and bones of the body provide locomotion, that is, the ability to move around and manipulate our surroundings. If it were not for locomotion, humans would be more dependent on the local environment. The human would not be able to move to avoid danger, find food and water, or erect shelter from the elements. Respiratory System The respiratory system takes oxygen into the body and gives off carbon dioxide waste products from the cells. The respiratory system includes the mouth, nose, trachea, or "wind pipe", bronchii, and the lungs. Deoxygenated blood from the right side of the heart passes through the lungs such that only 0.4 to 2.0 microns of membrane separates the air-carrying alveoli from pulmonary capillaries (i.e. tiny blood vessels). Gaseous oxygen diffuses across this membrane into the blood stream, while carbon dioxide comes out of the blood, into the alveoli, to be exhaled into the atmosphere.