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The brainstem is very small, making up around only 2.6 percent of the brain's total weight. [3] It has the critical roles of regulating heart and respiratory function, helping to control heart rate and breathing rate. [4] It also provides the main motor and sensory nerve supply to the face and neck via the cranial nerves.
Simple squamous epithelium falls under the physiological category of exchange epithelium due to its ability to rapidly transport molecules across the tissue layer. To facilitate this movement, some types of simple squamous epithelium may have pores between cells to allow molecules to move through it, creating a leaky epithelium.
For example, while basal cells in both the esophagus and the stomach function as multipotent progenitor cells, they are fundamentally different because the esophageal basal cells exist as a part of a stratified squamous epithelium, whereas the gastric basal cells exist as a part of a simple columnar epithelium. Functionally, this means that ...
The spinal cord is an extension of the brain. The spinal cord and the brain stem are joined at the base of the cranium at the foramen magnum. Most of the functions of the head and neck are directly influenced by the brain and transmitted to the PNS via the cranial nerves and spinal nerves of the cervical portion of the spine.
The cells of the brain include neurons and supportive glial cells. There are more than 86 billion neurons in the brain, and a more or less equal number of other cells. Brain activity is made possible by the interconnections of neurons and their release of neurotransmitters in response to nerve impulses.
In biology, tissue is an assembly of similar cells and their extracellular matrix from the same embryonic origin that together carry out a specific function. [ 1 ] [ 2 ] Tissues occupy a biological organizational level between cells and a complete organ .
In some tissues, a layer of columnar cells may appear to be stratified due to the placement of the nuclei. This sort of tissue is called pseudostratified. All glands are made up of epithelial cells. Functions of epithelial cells include diffusion, filtration, secretion, selective absorption, germination, and transcellular transport. Compound ...
Brain cells make up the functional tissue of the brain. The rest of the brain tissue is the structural stroma that includes connective tissue such as the meninges , blood vessels , and ducts. The two main types of cells in the brain are neurons , also known as nerve cells, and glial cells , also known as neuroglia. [ 1 ]