Biology

The skeleton of a tiger is an endoskeleton, made of the axial and appendicular skeletons. The axial skeleton is the skull, the auditory ossicles, the hyoid, the vertebrae, and the thoracic cage. The appendicular skeleton is the limbs and the pectoral and pelvic girdles.

The three types of joints in the body are fibrous, cartilaginous, and synovial. Fibrous joints are held together by fibrous connective tissue and have no movement. Cartilaginous joints are held together by cartilage and have very little movement. Synovial joints have a fluid-filled space between bones that allows for great movement.

There are three types of muscle in the body: skeletal muscle, smooth muscle, and cardiac muscle.

Skeletal muscles are attached to bones and can be intentionally controlled for movement, which gives it the second name of voluntary muscle. Skeletal muscle is striated.

Smooth muscle lines hollow internal organs, and is involuntary muscle. It has no striations.

Cardiac muscle is found only in the heart, and its contractions power the circulatory system. It is striated, but involuntary.

This diagram shows the location of a tiger's organs in its body, including the digestive system - the esophagus, the stomach, the small intestine, the large intestine, and the anus.

The digestive system is used to break down food and obtain nutrients. Digestion starts in the oral cavity and ends in the rectum. After being ingested, food boluses travel to the stomach via the esophagus. After the stomach, the chyme moves through the small and large intestines. Once all available nutrition and excess water have been absorbed, any substances left over are waste material and will be expelled by defecating. Accessory organs such as the liver, the pancreas, and the gallbladder also play a role in digestion.

Like all mammals and other vertebrates, tigers have a closed circulatory system. This system has double circulation. The muscular heart is the 'pump' of the system, sending blood through pulmonary (lungs) and systemic (body) circulations. The atria and ventricles of the heart contract, which creates the pressure differences that move blood through the arteries (away from the heart) and veins (toward the heart).

The respiratory system is all about gas exchange (breathing). Air comes in first through the nasal cavity and goes into the lungs by traveling through the pharynx and larynx, and the trachea.

This diagram shows the cellular structure of a neuron, which has specialized structures called dendrites and axons.

The nervous system is made of two types of cells: neurons and glia. Neurons exchange electric and chemical signals, which are sent by the axon and received by the dendrite. Glia are non-neuronal cells with many types and functions. Glial cells support the development and signaling of neurons.

The central nervous system (CNS) is composed of the brain and spinal cord. The peripheral nervous system (PNS) is composed of the autonomic nervous system (sympathetic and parasympathetic systems) and the sensory-somatic nervous system.