Histology Flashcards
Describe the three components of the homeostatic mechanism
- Receptor
- Integrator
- Effector
If there were a homeostatic imbalance with regards to pressure, what receptors detect this? where are they most commonly found?
- Baroreceptors
- Found in the Carotid artery
- It is important they are located in the Carotid artery because it pumps blood both to the heart and the brain.
What does -blast indicate?
forming or creating
What does -troph indicate?
feeding
What is the outer layer of cells called in fertilization?
-trophoblasts
What does the inner layer in fertilization become?
-The embryo proper
What do trophoblasts become?
-nutrient exchange in the placenta
Describe the overall process of the origin of tissues
- Beginning with fertilization sperm donates ½ of genome.
- Resulting fertilized egg is called the zygote (Fertilization happens far away from uterus).
-Start cell division right away, but we produce smaller and smaller cells (cell division aka cleavage) Oviduct or fallopian tube. Nutrients reserves in cytoplasm. Lots of nutrients there to supply to developing embryo. Cell division in early embryo is called cleavage.
-Little less than a week a solid ball of cells called morula then a couple of days later with continued mitosis hollow ball of cells inner cell mass embryo proper, outer layer of cells is trophoblast “feeding blast to form” trophoblast on outside of blastula become that organ of nutrient exchange for the embryo the placenta,
the inner cell mass part becomes the embryo.
-We set up this communication because there are messages releasing digestive enzymes that go into lining of uterus, some bleeding whole embryo embeds in the wall and there is a good blood supply for the embryo.
-Gastrulation is a process where the surface cells dive in and form 3 embryonic germ layers. That is differentiation. Ectoderm outside, mesoderm middle, endoderm inside. Gastrulation results in a 3 layered embryo. IN the embryo we end up with 3 embryonic germ layers. Their orientation and communication with each other guarantees that Only specific tissues will arise from these three types of embryonic cells.
What does the endoderm produce?
-Come from the primitive gut and becomes the digestive tract.
Where do tissues/nerves come from?
-ectoderm
Where do muscle and connective tissue come from?
-Mesoderm.
What process creates the third layer, mesoderm?
-Gastrulation
Describe Gastrulation in mammals
Gastrulation surface view. From bird, similar in mammals. Those embryonic cells of Ectoderm on the surface dive in and become mesoderm cells. Especially after implantation you see a change in shape as well as the size of the developing embryo. Those embryonic cells with ectoderm on the outer surface start to die and become mesoderm. Change in shape is morphogenesis. Gastrulation in particular creates the third layer mesoderm where before there were two layers.
What does the ectoderm make?
- The ectoderm makes the entire nervous system.
- One of the first to develop in embryon and one of the last to finish after birth.
- Nervous portions of eye and ear as well.
- Tooth enamel.
- The surface of the body = epidermis and all specializations of the epidermis.
- Brain and spinal cord, only makes sense they derived from ectoderm when you look at early development.
- The epidermis of the skin and its derivatives (including sweat glands, and hair follicles)
- Epithelial lining of mouth and anus
- Sensory receptors in epidermis
- Adrenal medulla
- Epithelium of pineal and pituitary glands on the outside
What does the mesoderm make?
- Skeleton, muscle tissues, the heart, blood, C/V, kidneys.
- Muscle and bone between the gut and dermis of skin
- Notochord
- Muscular layer of stomach and intestine
- Excretory system
- Circulatory and lymphatic systems
- Reproductive system(except germ cells)
- Lining of body cavity
- Adrenal cortex
What does the endoderm make?
- first formed as you are forming primitive gut.
- Tissues that line the gut are derived from endoderm and then all of the outerpocketings from there. This is why you share a respiratory tube with the digestive tract. (Pharynx is shared passageway betw/ respiratory and digestive. If you don’t use your flapper quite right, things will go into resp instead of digestive)
- Lining of respiratory system derived from endoderm.
- Ducts like liver and pancreas also derived from here.
- Ultimately, the Lining of the gut, you can go into glands, lungs, specializations of the lungs outpocketings of embryonic gut all of those are lined with tissues differentiated from endoderm.
- Lining of the urethra, urinary bladder, and reproductive system
- Liver, pancreas, Thymus, Thyroid, and parathyroid gland.
- Epithelial lining on the inside
What are the four basic tissue types and how are they different from the 3 embryonic germ layers?
- Four basic tissue types= Epithelial, Connective, Nervous, and muscular
- 3 embryonic germ layers named for position and the 4 basic tissue types: largely related to what they do.
- Related cells grouping together to share function. In a tissue, those cells have a common embryonic origin. Often they are held together by specific types of junctions.
Name the 5 intracellular junctions discussed in class
- Tight junctions, Adherens junctions, Gap junctions, Desmosomes, Hemidesmosomes
- Similar cells, common embryonic origin, if they are grouped together, they are held together by very similar intercellular junctions. Not likely that they will have all of them but they could have more than one.
Describe Tight junctions, where they are typically found and why
- Common in Transport epithelia
- Tight junctions are located nearer the luminal cell border rather than the basolateral border because we want the epithelial lining to be very sensitive, something has to essentially pass through two membranes before it gets into circulation.
- A folded lumen increases surface area, so we can have a lot of transporters at the lumen, may have other transporters at other locations.Where you have these tight junctions, absolutely nothing can sneak between cells. Each cell contributes proteins, helps to hold them together, where you have these nothing will sneak between the cells.
- Transport epithelium –> Boundary organ concept. Exchanging nutrients and waste and energy and materials with the outside environment. So you find them in boundary organs.
What do cilia do?
-Cilia are for movement, and they are made of microtubules 9+2 powered by ATP. Move things on the surface.
What do microvilli do?
-Increases surface area for absorption. Again you want it to be selective, and so you have specific transporters to bring things in. If you don’t have a transporter for it stays out, keeps on going. Very selective.
Describe Gap Junctions
- Very different. Composed of proteins. Barrels. Proteins that form tubes connect cytosol to cytosol. Allows movement of materials to move from one to the next.
- Functionally makes the cells united.
- You want cells to perform the same function but not at the same time.
- Common and necessary when cardiac muscle wants to contract. When you want all the cells to conduct electricity and contract at the same time. You want this in the heart. -So electrolytes move from one cell to another through gap junctions. Sodium and potassium can travel between the cells and so they can act like all one cell.
- The other good example is in the liver. Stores nutrients like a sponge. This allows us to more easily distribute (vitamins or glucose for example.) Liver metabolizes toxins. Anything that is not part of the normal composition.
Describe Desmosomes
- Found in Cardiac muscle and bladder tissue
- Contribute proteins to intercellular junctions, and provides more of a cell (cytoskeleton junction) than the other junctions.
- Don’t bring the cells that close together, you can imaging water and other materials to pass through. Tying cells together like Tennis shoes. Two parts of tennis shoes. Proteins that lace the two parts and you have reinforced material to keep water from getting in. Laces contacting two sides. Helps tissues resist physical stress. Like skin, and the heart
- This is why our skin comes out in sheets because they are connected by desmosomes
- Gap junctions allow quick movement, and desmosomes help’s with the physical stress. They work together!
Describe Hemidesomes
-Half of a desmosome
-Connect cells to extracellular material
Ex:// basement membrane
-We observe hemidesmosomes in epithelial cells
Describe general features of Epithelial Tissue
-Cover surfaces, line cavities and form glands.
Example of a gland:// Thyroid gland (One of the secreting unit of the thyroid gland is a pocket of cells called–> A thyroid follicle).
-Epithelial tissue is attached to underlying connective tissue by a basement membrane
-Avascular= without blood vessels. Therefore, nutrients diffuse in from blood vessels in underlying connective tissue
-Good nerve supply
-Rapid cell division that is responsive to environmental stress.
Describe Endocrine glands
- glands that secrete hormones into the bloodstream
- Purpose of this form of intercellular communication is to make widespread changes in metabolism. Growth, water balance, sugar metabolism…etc.
Describe Exocrine glands
- Excrete or release through a duct to a surface.
- could be to the outside of the body or could be to the lumen of an organ. Not into the bloodstream.
- Exocrine secretions: saliva, sweat, oil, tears, milk, mucus, bile (made by the liver), liver is a gland makes and secretes bile releases it through a duct which goes to gall bladder, over secretion there leads to salts, gets blocked
- Ex:// Goblet cells are exocrine– releasing mucus
Overall, what are the three primary functions of epithelial tissue?
- Protection (skin)
- Absorption (intestinal lining)
- Secretion (stomach lining)
ALL EPITHELIAL TISSUES ARE AVASCULAR
What function might the basement membrane serve in the repair of injury to the epithelium?
-How do you know how to heal? In part there are living cells around the outside capable of mitosis, and having at least some remnants of that basement membrane tell those cells you belong above this, divide by mitosis, and contact inhibition. Recognize the basement membrane and each other. This is what makes cancer different.
-We make mistakes and your immune system recognizes, and then your natural killer cells go out and mop them up.
If that doesn’t happen and epithelial cell turns into a cancerous cell, one of the aspects is that they do not respect boundaries of basement membrane. Gets into other systems. Lymph noed, circulatory system
