Description
The large intestine (or large bowel) is the last part of the digestive system.

The large intestine consists of the cecum, colon, rectum and anal canal. It starts in the right iliac region of the pelvis, just at or below the right waist, where it is joined to the bottom end of the small intestine. From here it continues up the abdomen, then across the width of the abdominal cavity, and then it turns down, continuing to its endpoint at the anus.

The large intestine is about 4.9 feet (1.5 m) long, which is about one-fifth of the whole length of the intestinal canal.

Function
The large intestine takes about 16 hours to finish the digestion of the food. It removes water and any remaining absorbable nutrients from the food before sending the indigestible matter to the liver. The colon absorbs vitamins which are created by the colonic bacteria - such as vitamin K (especially important as the daily ingestion of vitamin K is not normally enough to maintain adequate blood coagulation), vitamin B12, thiamine and riboflavin. It also compacts faeces, and stores faecal matter in the rectum until it can be discharged via the anus in defecation.

Colour
White.

Shape
Upside down U Shaped, like a thick snake.

Location
Within the abdomen between the small intestines and anus.

Parts of the large intestine are:

• Cecum – the first part of the large intestine
• Taeniae coli – three bands of smooth muscle
• Haustra – bulges caused by contraction of taeniae coli
• Epiploic appendages – small fat accumulations on the viscera

Locations along the colon are:

• The ascending colon
  
• The right colic flexure (hepatic)
  
• The transverse colon
  
• The transverse mesocolon
  
• The left colic flexure (splenic)
  
• The descending colon
  
• The sigmoid colon – the v-shaped region of the large intestine
  
  

Description
The average length of the small intestine in an adult human male is 6.9 m (22 feet 6 inches), and in the adult female 7.1 m (23 feet 4 inches). It can vary greatly, from as short as 4.6 m (15 feet) to as long as 9.8 m (32 feet). It is approximately 2.5–3cm in diameter.

The small intestine is divided into three structural parts: the Duodenum; Jejunum; and Ileum.

Function
The small intestine is where most chemical digestion takes place.The three major classes of nutrients that undergo digestion are proteins, lipids (fats) and carbohydrates. Digested food then able to pass into the blood vessels in the wall of the intestine through the process of diffusion. The small intestine is the site where most of the nutrients from ingested food are absorbed.

Absorption of the majority of nutrients takes place in the jejunum, with the following notable exceptions:

• Iron is absorbed in the duodenum.
• Vitamin B12 and bile salts are absorbed in the terminal ileum.
• Water and lipids are absorbed by passive diffusion throughout the small intestine.
• Sodium bicarbonate is absorbed by active transport and glucose and amino acid co-transport.

• Fructose is absorbed by facilitated diffusion.

Colour
White.

Shape
Like a very long coiled snake.

Location
From the duodenum to the large intestine within the abdomen.

Description
The stomach is a muscular, hollow, dilated part of the digestion system which functions as an important organ of the digestive tract in some animals, including vertebrates, echinoderms, insects (mid-gut), and molluscs. It is involved in the second phase of digestion, following mastication (chewing).

Function
Bolus (masticated food) enters the stomach through the oesophagus via the oesophageal sphincter. The stomach releases proteases (protein-digesting enzymes such as pepsin) and hydrochloric acid, which kills or inhibits bacteria and provides the acidic pH of two for the proteases to work. Food is churned by the stomach through muscular contractions of the wall called peristalsis – reducing the volume of the fundus, before looping around the fundus and the body of stomach as the boluses are converted into chyme (partially digested food). Chyme slowly passes through the pyloric sphincter and into the duodenum of the small intestine, where the extraction of nutrients begins. Depending on the quantity and contents of the meal, the stomach will digest the food into chyme anywhere between forty minutes and a few hours. The human stomach can hold approximately 1.5 litres of food.

Colour
Clear with whatever the colour of the food contents.

Shape
A "J" shaped pouch.

Location
The stomach is located in the upper left of the abdomen between the esophagus and the small intestine sitting just below the diaphragm.

Description
The word faeces comes from the Latin meaning "dregs”. Faeces are solid particle combinations of food residue, bacteria, and mucus. Human faecal matter varies significantly in appearance, depending on diet and health.

Normally it is semi-solid, with a mucus coating. Average weight of healthy adult faeces is 100-200 grams daily. Of this, 65% will be water and 35% dry matter.

Function
After eaten material has been digested, the remains of that material are expelled from the body as waste.

Colour
The normal brown colouration comes from a combination of bile, and bilirubin that comes from dead red blood cells. When ill the colour can vary from yellow, green or black.

Shape
Like small tubes of mud. It can be hard, soft, tarry, or liquid.

The Bristol Stool Form Guide itemises seven different types of feces.

Location
Solid matter excreted through the rectum and anus.

Description
The adult human brain weighs on average about 3lbs. (1.5kg) with a volume of around 1130 cubic centimetres (cm3) in women and 1260cm3 in men, although there is substantial individual variation.

The cerebral hemispheres form the largest part of the human brain and are situated above most other brain structures. They are covered with a cortical layer with a convoluted topography. Underneath the cerebrum lies the brain-stem, resembling a stalk on which the cerebrum is attached. At the rear of the brain, beneath the cerebrum and behind the brain-stem, is the cerebellum, a structure with a horizontally furrowed surface that makes it look different from any other brain area. The same structures are present in other mammals, although they vary considerably in relative size. As a rule, the smaller the cerebrum, the less convoluted the cortex. The cortex of a rat or mouse is almost perfectly smooth. The cortex of a dolphin or whale, on the other hand, is more convoluted than the cortex of a human.

Function
The brain is composed of neurons consisting of gray and white matter. The brain is the command centre sending impulses up to 170 mph down the spinal column and has nerve ending throughout the body.

Researchers who study the functions of the cortex divide it into three functional categories of regions, or areas. One consists of the primary sensory areas, which receive signals from the sensory nerves and tracts by way of relay nuclei in the thalamus. Primary sensory areas include the visual area of the occipital lobe, the auditory area in parts of the temporal lobe and insular cortex, and the somatosensory area in the parietal lobe. A second category is the primary motor area, which sends axons down to motor neurons in the brain-stem and spinal cord. This area occupies the rear portion of the frontal lobe, directly in front of the somatosensory area. The third category consists of the remaining parts of the cortex, which are called the association areas. These areas receive input from the sensory areas and lower parts of the brain and are involved in the complex process that we call perception, thought, and decision making.

Colour
Despite being referred to as grey matter, the live cortex is pinkish-beige in colour and slightly off-white in the interior.

Shape
Like a small very soft melon. The living brain is very soft, having a consistency similar to soft gelatin or soft tofu.

Location
In the cranium.

Description
Bile is a digestive fluid in the small intestines which comes from secretion of the liver and stored in the gall bladder. The human liver can produce close to one litre of bile per day. The Greeks spoke about excessive bile produced an aggressive temperament. Depression and other mental illnesses (melancholia) were ascribed to a bodily surplus of black bile. This is the origin of the word "melancholy".

Function
Bile is a digestive juice with an emulsifying action that facilitates digestion of fats in the intestines.

Colour
Straw colour from the liver and yellow, brown, or green in gallbladder.

Shape
Thick fluid, like car oil.

Location
The small intestines, liver, and gall bladder

Description
Thick sticky fluid mucus from the respiratory passages.

Function
Phlegm is produced by the respiratory system and particularly expelled by coughing (sputum). Its composition varies, depending on climatic, genetic and state of the immune system, but basically is a water-based gel consisting in glycoproteins, immunoglobulins, lipids, etc.

Colour
Healthy phlegm is normally clear or white. Yellow phlegm is normally a sign of an infection in the case of the common cold. Greenish or brownish phlegm is nearly always a sign of infection. Greenish or rusty phlegm or phlegm with rusty spots can also be a sign of pneumonia and/or internal micro-bleedings.

Shape
Thick fluid.

Location
In the lung, throat and mouth.

Description
An exudate fluid that filters from the circulatory system into lesions or areas of inflammation. Pus consists of a thin, protein-rich fluid, known as liquor puris, and dead leukocytes from the body's immune response (mostly neutrophils). An accumulation of pus in an enclosed tissue space is known as an abscess, whereas a visible collection of pus within or beneath the epidermis is known as a pustule or pimple.

Function
During infection, macrophages release cytokines which trigger neutrophils to seek the site of infection by chemotaxis. There, the neutrophils engulf and destroy the bacteria and the bacteria resist the immune response by releasing toxins called leukocidins. As the neutrophils die off from toxins and old age, they are destroyed by macrophages, forming the viscous pus.

Color
Typically white-yellow, yellow, or yellow-brown. Occasionally with blood.

Shape
Thick liquid that fills a cavity.

Location
Anywhere in body.

Blood

Description

Fluid that circulates throughout the heart, arteries, veins and capillaries carrying nourishment, electrolytes, hormones, vitamins, antibodies, heat, and oxygen to the tissues and taking away waste matter. Blood consists of 22% solids and 78% liquid. Red blood cells are formed at the rate of 2 million per second. Within a tiny droplet of blood, there are 5 million red blood cells, 300,000 platelets and 10,000 white cells. The human body contains from 8- 10 pints of blood.

Function

• Supply of oxygen to tissues.
• Supply of nutrients such as glucose, amino acids, and fatty acids.
• Removal of waste such as carbon dioxide, urea, and lactic acid.
• Immunological functions, including circulation of white blood cells, and detection of foreign material by antibodies.
• Coagulation, which is one part of the body's self-repair mechanism.
• Messenger functions, including the transport of hormones and the signalling of tissue damage.
• Regulation of body pH.
• Regulation of core body temperature.
• Hydraulic functions.

Colour
From dark to bright red.

Shape
liquid.

Location
In heart, arteries, veins and capillaries.