The stomach is a muscular, hollow organ in the gastrointestinal tract of humans and many other animals, including several invertebrates. The stomach has a dilated structure and functions as a vital digestive organ. In the digestive system the stomach is involved in the second phase of digestion, following mastication (chewing).
In humans and many other animals, the stomach is located between the oesophagus and the small intestine. It secretes digestive enzymes and gastric acid to aid in food digestion. The pyloric sphincter controls the passage of partially digested food (chyme) from the stomach into the duodenum where peristalsis takes over to move this through the rest of the intestines.
The kidneys are two bean-shaped organs found on the left and right sides of the body in vertebrates. They filter the blood in order to make urine, to release and retain water, and to remove waste and nitrogen (the excretory system). They also control the ion concentrations and acid-base balance of the blood. Each kidney feeds urine into the bladder by means of a tube known as the ureter. In humans, they are roughly 11 centimetres (4.3 in) in length.
The kidneys regulate the balance of ions known as electrolytes in the blood, along with maintaining acid base homeostasis. They also move waste products out of the blood and into the urine, such as nitrogen-containing urea and ammonium. Kidneys also regulate fluid balance and blood pressure. They are also responsible for the reabsorption of water, glucose, and amino acids. The kidneys also produce hormones including calcitriol and erythropoietin. The kidneys also make an important enzyme, renin, which affects blood pressure through negative feedback.
The lungs are the primary organs of the respiratory system in humans and many other animals including a few fish and some snails. In mammals and most other vertebrates, two lungs are located near the backbone on either side of the heart. Their function in the respiratory system is to extract oxygen from the atmosphere and transfer it into the bloodstream, and to release carbon dioxide from the bloodstream into the atmosphere, in a process of gas exchange. Respiration is driven by different muscular systems in different species. Mammals, reptiles and birds use their different muscles to support and foster breathing. In early tetrapods, air was driven into the lungs by the pharyngeal muscles via buccal pumping, a mechanism still seen in amphibians. In humans, the main muscle of respiration that drives breathing is the diaphragm. The lungs also provide airflow that makes vocal sounds including human speech possible.
The small intestine or small bowel is the part of the gastrointestinal tract between the stomach and the large intestine, and is where most of the end absorption of food takes place. The small intestine has three distinct regions – the duodenum, jejunum, and ileum. The duodenum is the shortest part of the small intestine and is where preparation for absorption begins. It also receives bile and pancreatic juice through the pancreatic duct, controlled by the sphincter of Oddi. The primary function of the small intestine is the absorption of nutrients and minerals from food, using small finger-like protrusions called villi.
The large intestine, also known as the large bowel or colon, is the last part of the gastrointestinal tract and of the digestive system in vertebrates. Water is absorbed here and the remaining waste material is stored as feces before being removed by defecation.
Most sources define the large intestine as the combination of the cecum, colon, rectum, and anal canal. Some other sources exclude the anal canal.
The heart is a muscular organ in humans and other animals, which pumps blood through the blood vessels of the circulatory system. Blood provides the body with oxygen and nutrients, as well as assists in the removal of metabolic wastes. In humans, the heart is located between the lungs, in the middle compartment of the chest.
In humans, other mammals, and birds, the heart is divided into four chambers: upper left and right atria; and lower left and right ventricles. Commonly the right atrium and ventricle are referred together as the right heart and their left counterparts as the left heart. Fish, in contrast, have two chambers, an atrium and a ventricle, while reptiles have three chambers. In a healthy heart blood flows one way through the heart due to heart valves, which prevent backflow. The heart is enclosed in a protective sac, the pericardium, which also contains a small amount of fluid. The wall of the heart is made up of three layers: epicardium, myocardium, and endocardium.
The human brain is the central organ of the human nervous system, and with the spinal cord makes up the central nervous system. The brain consists of the cerebrum, the brainstem and the cerebellum. It controls most of the activities of the body, processing, integrating, and coordinating the information it receives from the sense organs, and making decisions as to the instructions sent to the rest of the body. The brain is contained in, and protected by, the skull bones of the head. The cerebrum is the largest part of the human brain. It is divided into two cerebral hemispheres. The cerebral cortex is an outer layer of grey matter, covering the core of white matter. The cortex is split into the neocortex and the much smaller allocortex. The neocortex is made up of six neuronal layers, while the allocortex has three or four. Each hemisphere is conventionally divided into four lobes – the frontal, temporal, parietal, and occipital lobes. The frontal lobe is associated with executive functions including self-control, planning, reasoning, and abstract thought, while the occipital lobe is dedicated to vision. Within each lobe, cortical areas are associated with specific functions, such as the sensory, motor and association regions. Although the left and right hemispheres are broadly similar in shape and function, some functions are associated with one side, such as language in the left and visual-spatial ability in the right. The hemispheres are connected by nerve tracts, the largest being the corpus callosum.
Submitted by: Jhymarie C. Lorella
IV - Capricorn
Submitted to: Mariefa Joy S. Daguro