Organ (biology)

Your body has many parts.

These parts are called organs. An organ is made of many tissues. These tissues work together to do one job.

Plants have organs too. Roots and stems are plant organs. Flowers are also organs for plants.

Many organs work together in a group. These groups are called organ systems. This helps your body stay healthy.

An organ is a group of tissues. These tissues work together to do a job.

Tissues are made of many cells. Different tissues join to make one organ.

Organs have two main parts. The first is the parenchyma. This is the part that does the main work. The second is the stroma. This part provides support. It includes things like blood vessels. These vessels bring food and oxygen to the organ.

Many organs work in a group. These groups are called organ systems. For example, the heart and blood vessels form the cardiovascular system.

Plants also have organs. They have vegetative organs like roots and leaves. They also have reproductive organs. In flowers, these are the parts that make seeds.

Some plants use cones to reproduce. Scientists study how these organs change over time. This helps us learn how life grew and changed.

An organ is a special group of tissues. These tissues join together to do a specific job. In the hierarchy of life, an organ sits between tissue and an organ system. Tissues are made of the same kind of cells working together. When different types of tissues combine, they form an organ. For example, the wall of an intestine uses epithelial tissue and smooth muscle tissue.

This teamwork allows the organ to perform its unique role in a living thing.

Organs have two main parts that work in different ways. The first is called the parenchyma. This is the functional tissue that does the main work. The second part is called the stroma. This is the structural tissue that provides support and connection. The stroma includes things like nerves and blood vessels. These vessels nourish the parenchyma with oxygen and remove waste.

This structure ensures the organ stays in the right place and stays healthy.

Many organs work together in groups called organ systems. For instance, the heart and blood vessels form the cardiovascular system. This system pumps and moves blood throughout the body. The digestive system uses many organs like the stomach and intestines to process food.

Some systems even overlap. The nervous and endocrine systems both use the hypothalamus. Because they share this organ, they are sometimes studied together as the neuroendocrine system. There are about 79 organs in the human body.

Plants also rely on organs to live and grow. They have vegetative organs like roots, stems, and leaves. These parts help the plant stay alive and grow.

Plants also have reproductive organs. In flowering plants, these are the flowers, seeds, and fruits. Some plants, like conifers, use cones instead. Other plants use structures called strobili or gametophores. These organs are essential for making new generations of plants.

Scientists have studied organs for a very long time. Aristotle used the word "organ" to mean a tool. He believed body organs were tools for doing things.

Long ago, some people even looked at animal organs to try to predict the future. Today, doctors use organ transplants to help people. They move an organ from a donor to someone who is sick. Researchers are even working to grow new organs in laboratories.

In multicellular organisms, an organ is a structural unit made of various tissues. These tissues join together to perform a specific, common function. Within the hierarchy of biological organization, an organ occupies the level between tissue and an organ system. Tissues consist of similar cells working together for a single purpose. When different tissue types combine, they form an organ with a specialized role. For example, the intestinal wall is composed of both epithelial tissue and smooth muscle tissue.

An organ is generally composed of two distinct types of tissue: parenchyma and stroma. The parenchyma is the functional tissue that performs the organ's primary job. For instance, in a gland, the parenchyma is the tissue that actually produces hormones. The stroma is the structural tissue that provides support and connection. It includes connective tissues that anchor the organ in place. The stroma also contains nerves that innervate the parenchyma. Additionally, blood vessels in the stroma oxygenate the parenchyma and remove metabolic wastes.

When two or more organs work together, they form an organ system. These systems are also known as biological or body systems. In humans, there are approximately 79 organs, though the exact number is debated. Many systems share overlapping functions and organs. The nervous and endocrine systems both utilize the hypothalamus. Because of this shared organ, scientists often study them together as the neuroendocrine system. Similarly, the muscular and skeletal systems are often studied as the musculoskeletal system.

Human organ systems serve many vital roles. The cardiovascular system uses the heart and blood vessels to pump blood. The digestive system includes the stomach, liver, pancreas, and intestines to process food. The respiratory system uses the lungs and diaphragm for breathing. The endocrine system uses glands like the thyroid and adrenals to communicate via hormones. The excretory system, including the kidneys and bladder, manages fluid and electrolyte balance. The integumentary system consists of the skin, hair, and nails.

Plants also rely on organs, which are divided into vegetative and reproductive structures. Vegetative organs, such as roots, stems, and leaves, are essential for maintaining the plant's life. Reproductive organs vary by plant type. In flowering plants, these include the flower, seed, and fruit.

Conifers use cones to bear reproductive structures. Other plants use strobili or gametophores. In many plants, the shoot organ system includes everything above the ground, such as leaves and flowers.

Organ evolution has occurred over hundreds of millions of years. In animals, the organ level of organization is first seen in flatworms. More complex animals evolved organs over long periods. The gut and brain are very ancient, appearing in ancestors of vertebrates and insects about 700 to 650 million years ago. The liver and heart evolved later in chordates, roughly 550 to 500 million years ago. Researchers study the placenta as a model because it has evolved independently more than 100 times in vertebrates. This helps scientists understand how tissues repurpose themselves to form new organs.

Humanity has a long history of studying organs. The English word "organ" once referred to musical instruments in the 12th century. In ancient Greece, Aristotle used the word "organon," meaning "tool," to describe organs. He believed body parts were tools for living. In the 20th century, medical science began performing organ transplants. This involves moving an organ from a donor to a patient with a failing organ. Today, scientists are working on xenotransplantation, which uses animal tissues like porcine heart valves. There is also significant research into creating artificial or laboratory-grown organs.