EPITHELIAL TISSUE

-
EPITHELIAL TISSUE KEY FACTS
  • Epithelial tissue is composed of cells laid together in sheets with the cells tightly connected to one another. Epithelial layers are avascular, but innervated.
  • Epithelial cells have two surfaces that differ in both structure and function.
  • Glands, such as exocrine and endocrine, are composed of epithelial tissue and classified based on how their secretions are released.

Functions of the Epithelium

Epithelia tissue forms boundaries between different environments, and nearly all substances must pass through the epithelium. In its role as an interface tissue, epithelium accomplishes many functions, including:
  1. Protection for the underlying tissues from radiation, desiccation, toxins, and physical trauma.
  2. Absorption of substances in the digestive tract lining with distinct modifications.
  3. Regulation and excretion of chemicals between the underlying tissues and the body cavity.
  4. The secretion of hormones into the blood vascular system. The secretion of sweat, mucus, enzymes, and other products that are delivered by ducts come from the glandular epithelium.
  5. The detection of sensation.

Characteristics of Epithelial Layers

Epithelial tissue is composed of cells laid out in sheets with strong cell-to-cell attachments. These protein connections hold the cells together to form a tightly connected layer that is avascular but innervated in nature.
The epithelial cells are nourished by substances diffusing from blood vessels in the underlying connective tissue. One side of the epithelial cell is oriented towards the surface of the tissue, body cavity, or external environment and the other surface is joined to a basement membrane. The basement layer is non-cellular in nature and helps to cement the epithelial tissue to the underlying structures.

Types of Epithelial TissueResultado de imagen de EPITHELIAL TISSUE

Epithelial tissues are identified by both the number of layers and the shape of the cells in the upper layers. There are eight basic types of epithelium: six of them are identified based on both the number of cells and their shape; two of them are named by the type of cell (squamous) found in them. Epithelial tissue is classified based on the number of cells, the shape of those cells, and the types of those cells.
This illustration shows the three principal classifications associated with epithelial cells. Squamous epithelium has cells that are wider than they are tall. Cuboidal epithelium has cells whose height and width are approximately the same. Columnar epithelium has cells taller than they are wide. There are pictures of each of these types of epithelium: simple squamous, simple cuboidal, simple columnar, stratified squamous, stratified cuboidal, pseudostratifed columnar, and transitional.

Comentarios

Publicar un comentario

Entradas populares de este blog

HUMAN EMBRYOGENESIS (STEP 1-4)

-
Imagen
Embryogenesis, the first eight weeks of development after fertilization, is an incredibly complicated process. It’s amazing that in eight weeks we’re transforming from a single cell to an organism with a multi-level body plan. The circulatory, excretory, and neurologic systems all begin to develop during this stage. Luckily, like with many complex biological concepts, fertilization can be broken down into smaller, simpler ideas. The big idea of embryogenesis is going from a single cell to a ball of cells to a set of tubes.  Starting from the very beginning Step 1 : a  zygote  is the single cell formed when an egg and a sperm cell fuse; the fusion is known as fertilization Step 2 : the first 12-to 24-hours after a zygote is formed are spent in  cleavage  – very rapid cell division The zygote’s first priority is dividing to make lots of new cells, so it’s first few days are spent in rapid mitotic division. With each round of division, it doubles in c...
Leer más

CENTRAL NERVOUS SYSTEM

-
Imagen
The Central Nervous System (CNS) The central nervous system is divided into two major parts: the brain and the spinal cord.   Firstly,we are going to talk about the brain. Parts of the Human Brain and their Subdivisions Human encephalon resembles, in structure and function, with that of the other vertebrates. The scientists reveal that parts of the human brain are Forebrain, Midbrain & Hindbrain and the related structures that collectively act as a single highly specialized unit. These parts work in coordination and perform  different functions of brain . More specifically, it is divided into five major regions, namely, telencephalon, diencephalon or inter-brain, myelencephalon (hindbrain/medulla oblongata), metencephalon and mesencephalon (midbrain). Here follows a precise but comprehensive description of each of the above given divisions. Telencephalon/Cerebrum—Anterior Part Of Forebrain Further composed of cerebral cortex, limbic and basal ganglia,...
Leer más

ANATOMY OF THE KNEE

-
Imagen
The knee is one of the largest and most complex joints in the body. The knee joins the thigh bone (femur) to the shin bone (tibia). The smaller bone that runs alongside the tibia (fibula) and the kneecap (patella) are the other bones that make the knee joint. Tendons connect the knee bones to the leg muscles that move the knee joint. Ligaments join the knee bones and provide stability to the knee: The anterior cruciate ligament prevents the femur from sliding backward on the tibia (or the tibia sliding forward on the femur). The posterior cruciate ligament prevents the femur from sliding forward on the tibia (or the tibia from sliding backward on the femur). The medial and lateral collateral ligaments prevent the femur from sliding side to side. Two C-shaped pieces of cartilage called the medial and lateral menisci act as shock absorbers between the femur and tibia. Numerous bursae, or fluid-filled sacs, help the knee move smoothly.
Leer más

SKELETAL SYSTEM (TYPES OF BONES AND PARTS)

-
Imagen
The skeletal system includes all of the bones and joints in the body. Each bone is a complex living organ that is made up of many cells, protein fibers, and minerals. The skeleton acts as a scaffold by providing support and protection for the soft tissues that make up the rest of the body. The skeletal system also provides attachment points for muscles to allow movements at the joints. New blood cells are produced by the red bone marrow inside of our bones. Bones act as the body’s warehouse for  calcium, iron, and energy in the form of fat. Finally, the skeleton grows throughout childhood and provides a framework for the rest of the body to grow along with it. Skeletal System Anatomy The skeletal system in an adult body is made up of 206 individual bones. These bones are arranged into two major divisions: the  axial skeleton  and the  appendicular skeleton .   Types of Bones All of the bones of the body can be broken down into five types: long, sho...
Leer más