¶ … nervous and digestive systems at reptiles, emphasizing their main characteristics and briefly compare them to the nervous and digestive systems at other vertebrates. In this sense, referring to the reptilian nervous systems, many authors have found common basis and similarities between the nervous systems of reptiles and other higher vertebrates, including mammals

These similarities manifest themselves both in the form of anatomical and physiological resemblances. The main difference between the reptilian brain and that of higher vertebrates such as mammals relates to "the size of the cerebral hemispheres"

As such, the reptilian nervous system is formed of two different components: the central nervous system (CNS) and the peripheral nervous system (PNS). The central nervous system is composed of the brain and the spinal cord, while the peripheral nervous system is composed of all nervous tissues and structures that do not actually belong to the CNS.

As at other vertebrates, the brain, constituent part of the central nervous system, is protected by the skull. The bones forming the skull similarly have names such as parietal and occipital, which also form the human skull, for example. The brain is spaced by the subdural and epidural spaces within the skull and the volume of these substances varies across different species. As such, at aquatic turtles or lizards, there is a considerable space between the brain and the endocranial cavity, while at many others, including snakes, there is little space

. The spinal cord goes along the backside, in many cases to the tip of the tail.

Physiologically speaking, the reptilian brain is divided intro three different regions, each serving a well-defined purpose. The forebrain performs smell and taste functions, as well as sensory-motor ones. The midbrain "is associated with visual processing and neuroendocrine functions"

, while the hindbrain has hearing,...

These olfactory bulbs are better developed in the case of reptiles that require strong olfactory skills, such as crocodiles, and that have the afferent olfactory tracts leading from the bulbs to the cerebrum.
The cranial nerves, located ventrally and laterally on the brain, perform the most vital functions of the reptilian body. A reptile will have 12 or 13 reptile nerves. These nerves include the olfactory and optic nerves, the oculomotor nerve (which controls the movement of the eye), the facial nerve (with sensory functions) and the spinal and hypoglossal nerves, controlling muscles in the body.

Additional to the cranial nerves, reptiles will also have spinal nerves, located in the spinal cord and performing visceral and motor functions. All these series of nerves communicate with each other by transmitting messages either through electrical or chemical signals and can be classified as having either excitatory or inhibitory roles.

Reflecting on this brief presentation of the reptiles' nervous systems, we find that many anatomical characteristics, such as the position of the brain or the spinal cord, are in close resemblance to the human and higher vertebrates one. In terms of physiological necessities, the reptilian nervous system has developed to provide the best adaptation of the reptiles' necessities, with emphasis on sight or smell and motor functions.

The digestive system is in many ways similar as well

. The main components present in higher vertebrates can be recognized in modern reptiles too. This includes the present of a mouth (oral cavity) and salivary glands, esophagus, stomach, and intestine, ending in the cloacae

. Let's have a brief look at each.

Some reptiles, such as lizards or snakes, swallow their…