Histology + Physiology + Anatomy PDF

Histology + Physiology + Anatomy Histology part: 1. Principal characteristics of epithelium One of the four major tissues of the body and it can be. Can be found in the respiratory tract, the digestive tract, the epidermis of the skin, the oral cavity and many of the glands. Epithelial tissues have...

Histology + Physiology + Anatomy Histology part: 1. Principal characteristics of epithelium One of the four major tissues of the body and it can be. Can be found in the respiratory tract, the digestive tract, the epidermis of the skin, the oral cavity and many of the glands. Epithelial tissues have some common characteristics, they are tightly packed cells with very little extracellular space. They also have an apical or free surface that is exposed to an internal body space or the external environment. And a basal or deep surface that is attached to a thin basement membrane, which is connected to connective. They also lack blood vessels, which is called avascular, so they get nutrients from their apical free surface, or by diffusion across their basal surface from the underlying connective tissue. Epithelial tissue is also innervated which means that they have a rich supply of nerves, and epithelial cells can reproduce themselves, which is important because they go through severe wear and tear, such as in the skin and the respiratory and digestive tracts. Epithelial tissue has several important functions, it provides protection, just like the skin. It protects the internal body from bacteria and other harmful substances, it provides sensory functions in the skin, nose, eyes and ears. Epithelial cells are also very important in secretions, as they secrete hormones, sweat, digestive juices and mucus. And epithelial tissue is important in absorption, such as nutrients in the gut, and the exchange of gasses in the lungs. 2. Classification and structural peculiarities of simple and stratified epitheliums Different types of epithelial cells: Squamous- thin and flat Cuboidal- cube shaped Columnar- more tall than wide Pseudostratified- varying forms Goblet cells- which secrete mucin Microvilli- like tiny fingers, which helps to increase the surface area for digestion and absorbing nutrients in the intestine. Classified in three different ways: Simple epithelium- Is only one cell layer thick and all cells are in direct contact with the basement membrane. There is simple squamous, simple cuboidal and simple columnar epithelial. Stratified epithelium- Have two or more layers of cells, only the deepest basal layer cells have direct contact with a basement membrane, and their formation looks like a brick wall. This formation provides better structural support and protection from wear or tear. There are stratified squamous, stratified cuboidal, stratified pseudostratified. Pseudostratified epithelium- Is comprised of pseudostratified cells. Transitional epithelium relaxed- In a relaxed state they have umbrella looking rounded cells at the top apical surface and the bottom basal cells appear cuboidal. Transitional epithelium stretched- The top cells flatten and appear squamous. Some of these cells will also have two nuclei. Keratinized stratified squamous epithelium- In which the top superficial layers of cells are dead. As new cells are produced in the basal bottom region, they migrate to the top and they produce a protein called keratin. These cells fill with the kreatin, which make them very strong, but they lose their organelles and nuclei die. The epidermis or outer layer of the skin consists of keratinized stratified squamous epithelium. 3. Structure and classification of glands Glands are multicellular organs or individual cells that secrete substances for use in the body. Most glands are made up of epithelial tissue and their seat creations include mucin, hormones, sweat, enzymes, electrolytes and waste products. Can be divided into 2 groups: Endocrine glands- Secrete their products, mainly hormones, directly into the bloodstream or intestinal fluid that surrounds cells. Some endocrine glands include the adrenal, thyrióid and pituitary glands. Exocrine glands- Typically secrete their products into a duct or onto a surface such as the skin, but not into the bloodstream. Exocrine glands can be unicellular or multicellular. Unicellular exocrine glands do not contain duct and the multicellular glands do contain a duct system. An example of a unicellular exocrine gland is the goblet cell, which can be found in the epithelial tissue and secrete mucin, which forms a mucous layer, coating certain tissue areas, such as the air passageway in the trachea, in the respiratory system. Classified in 2 different ways: By their form: - Simple glands- Which have a single duct - Compound glands- Which have branching ducts. - Tubular- where the diameter of the duct and secretory portion are similar - Acinar or alveolar- where the secretory portion of the gland forms a sac like shape - Simple straight tubular- A single, unbranched tube-shaped gland. Example intestinal glands. - Coiled tubular- A single tube that coils in on itself. Example, sweat glands - Simple branched tubular- Multiple tubular branches extending from a single duct. Example, glands in the stomach - Simple acinar- A single, rounded, flask-like gland. Example sebaceous glands - Simple branched acinar- Multiple acinar (rounded) glands connected to a single duct. Example sebaceous glands in the skin. - Compound tubular- Multiple tubular branches connected to multiple ducts, forming a complex structure. Example, Brunner’s glands in the duodenum. - Compound acinar- Multiple rounded, acinar structures connected to a branched duct system. Example, mammary glands - Compound tubuloacinar- A combination of tubular and acinar structures in a complex branched duct system. Example, salivary glands. 4. Mechanisms of gland secretion By their secretion method (2 forms): - Holocrine glands- Accumulate a secretory product and the entire cell ruptures to release the ruptured cells are replaced by other epithelial cells through cell division. Examples of holocrine glands include certain glands in the skin and in the eyelids. - Merocrine glands- release their secretions through the process of exocytosis, where secretory vesicles are released through the plasma membrane of the cell without damaging the cell itself. The salivary glands are an example of merocrine glands. - Apocrine- Pinch off a portion of the cell to release their secretory products. The repairs itself and continues to release its products in the same manner, mammary and some sweat glands are examples of apocrine glands. 5. Classification and structure of neurons The central nervous system- is your brain and spinal cord, the main control center. It decides whether to remove a spider that's sitting on your arm or not, by giving order to your hand. Peripheral nervous system- is composed of all the nerves that branch off from the brain and spine that allow your central nervous system to communicate with the rest of your body. It's working in both directions, from the brain to the body and from the body to the brain. The neuron (nerves cells): That respond to stimuli and transmit signals. These neurons are surrounded and protected by neuroglia or glial cells. Sensory neurons- Pick up messages and transmit impulses from sensory receptors in say, the skin or internal organs and send them towards the central nervous system. (Mostly unipolar neurons). Motor neurons- They are mostly multipolar, and transmit impulses away from the central nervous system and out to your body’s muscles and glands. Interneurons- Which live in the central nervous system and transmit impulses bw those sensory and motor neurons. Interneurons are the most abundant of your body’s neurons and are mostly multipolar. Unipolar Multipolar Bipolar Structure: Soma (cell body)- is the neuron’s life support. It contains the nucleus, DNA, mitochondria, ribosomes, cytoplasm. Dendrites- They’re the listeners, they pick up messages, news, gossip from other cells and convey that information to the cell body. Axon- Is like the talker. The long extension, or fiber, can be super short or run a full meter from your spine down to your ankle. The axon transmits electrical impulses away from the cell body to the other cells. Multipolar neurons- With three or more processes sticking out of the soma- including one axon and a bunch of dendrites. Bipolar neurons- Have two processes, an axon and a single dendrite, extending from opposite. Unipolar neurons- Have just one process and are found mostly in our sensory receptors. Synapse- Neurons communicate with other neurons by effectors cells by specialized junctions called synapses. 6. Classification and structure of central and peripheral neuroglia cells In the central nervous system: - Astrocytes- Star-shaped astrocytes are found in your central nervous system and are your most abundant and versatile glial cells. They anchor neurons to their blood supply, and govern the exchange of materials bw neurons and capillaries. - Microglial cells- Are the protective cells, they are smaller and act as the main source as the immune defense against invading microorganisms in the brain and spinal cord. - Ependymal cells- Line cavities in your brain and spinal cord and create, secrete and circulate cerebrospinal fluid that fills those cavities and cushions those organs. - Oligodendrocytes- Wrap around neurons, producing and insulating barrier called the myelin sheath In the peripheral system: - Satellite cells- Do mainly in the peripheral system what astrocytes cells do in the central system. They surround and support neuron cell bodies. - Schwann cells- Are similar to our oligodendrocytes, in that they wrap around axons and make that insulating myelin sheath. 7. Structure of peripheral nerve Myelinated axons- An individual Schwann cell envelops a single axon multiple times. Unmyelinated axon- The axons are myelinated, but a single Schwann cell envelopes several axons, and does not form tightly wrapped layers around the axon. Instead the axons sit in grooves in the surfaces of the cells Endoneurium- Surrounds each individual nerve fiber and associate Schwann cell Perineurium- Surrounds each nerve fascicle Epineurium- Surrounds a peripheral nerve and fills the spaces bw nerve fascicle