The human body is the entire structure of a human being. It is composed of many different types of cells that together create tissues and subsequently organ systems. They ensure homeostasis and the viability of the human body.  It comprises a head, neck, trunk (which includes the thorax and abdomen), arms and hands, legs and feet.

The study of the human body involves anatomy, physiology, histology and embryology. The body varies anatomically in known ways. Physiology focuses on the systems and organs of the human body and their functions. Many systems and mechanisms interact in order to maintain homeostasis, with safe levels of substances such as sugar and oxygen in the blood.

The human body has four limbs (two arms and two legs), a head and a neck which connect to the torso. The body's shape is determined by a strong skeleton made of bone and cartilage, surrounded by fat, muscle, connective tissue, organs, and other structures. The spine at the back of the skeleton contains the flexible vertebral column which surrounds the spinal cord, which is a collection of nerve fibres connecting the brain to the rest of the body. Nerves connect the spinal cord and brain to the rest of the body. All major bones, muscles, and nerves in the body are named, with the exception of anatomical variations such as sesamoid bones and accessory muscles.

Blood vessels carry blood throughout the body, which moves because of the beating of the heart. Venules and veins collect blood low in oxygen from tissues throughout the body. These collect in progressively larger veins until they reach the body's two largest veins, the superior and inferior vena cava, which drain blood into the right side of the heart. From here, the blood is pumped into the lungs where it receives oxygen and drains back into the left side of the heart. From here, it is pumped into the body's largest artery, the aorta, and then progressively smaller arteries and arterioles until it reaches tissue. Here blood passes from small arteries into capillaries, then small veins and the process begins again. Blood carries oxygen, waste products, and hormones from one place in the body to another. Blood is filtered at the kidneys and liver.

The body consists of a number of different cavities, separated areas which house different organ systems. The brain and central nervous system reside in an area protected from the rest of the body by the blood brain barrier. The lungs sit in the pleural cavity. The intestines, liver, and spleen sit in the abdominal cavity.  Height, weight, shape and other body proportions vary individually and with age and sex. Body shape is influenced by the distribution of muscle and fat tissue.

Body image is a person's perception of the aesthetics or sexual attractiveness of their own body. The phrase body image was first coined by the Austrian neurologist and psychoanalyst Paul Schilder in his book The Image and Appearance of the Human Body (1935). Human society has at all times placed great value on beauty of the human body, but a person's perception of their own body may not correspond to society's standards.

The concept of body image is used in a number of disciplines, including psychology, medicine, psychiatry, psychoanalysis, philosophy and cultural and feminist studies. The term is also often used in the media. Across these disciplines and media there is no consensus definition. A person's body image is thought to be, in part, a product of their personal experiences, personality, and various social and cultural forces. A person's sense of their own physical appearance, usually in relation to others or in relation to some cultural "ideal," can shape their body image. A person's perception of their appearance can be different from how others actually perceive them.

Body image can have a wide range of psychological effects and physical effects. Throughout history, it has been extremely difficult for people to live up to the standards of society and what they believe the ideal body is. There are many factors that lead to a person’s body image, some of these include: family dynamics, mental illness, biological predispositions and environmental causes for obesity or malnutrition, and cultural expectations (e.g., media and politics). People who are both underweight and overweight can have poor body image. However, because people are constantly told and shown the cosmetic appeal of weight loss and are warned about the risks of obesity, other scholars have expressed concern that these claims are not based on solid data. those who are normal or overweight on the BMI scale have higher risks of poor body image. This is something that can lead to a change in a person's body image.