We dissected a heart this past valentines day, a bit ironic i know. In this lab, we had to measure some of the more...important parts of the heart. We measured the diameter of the Aorta, Pulmonary Trunk, right and left atrium, right and left ventricles, and the outer walls. We measured all of those things on 3 different species' hearts. There was the Sheep heart, Pig heart, and the Cow heart. Though the basic structure of these hearts were pretty much the same, the major difference in them came in the overall size of the parts we had to measure. For instance, the Sheep heart was no bigger than ones hand, where as the cow heart was massive! So you could conclude that it was easier to find things like the Aorta on the cow heart than the sheep heart. The reason for this extreme size difference in the hearts, could be contributed to the amount of blood that needs to be pumped into the body, so a cow needs to have more blood going through their body than a sheep needs to go through theirs. An interesting fact about the pig heart, is that it is about the same size as a human heart. Therefore the human and the pig need about the same amount of blood pushed throughout their bodies.
One of the questions that we were asked to find out by using the microscope and analyzing parts of the veins outer wall, and an arteries outer wall, was what is thicker, the wall of the veins or the walls of the arteries. The answer is the walls of the arteries, because they have more blood flowing through them at a faster rate than veins do. As for the Cardiac muscle (around the heart), it is a striated muscle, where as most other muscles are silky smooth. After viewing that, we went ahead and looked at a coronary artery with atherosclerosis, which is a kind of plaque that builds up in some arteries, which can then restrict the blood flow, and possibly cause a blood clot.
The sheep heart had the largest right side outer wall at 5 cm, and the pig heart has the largest left side outer wall coming in at 4 cm. In terms of overall size, the cow heart is the largest, yet in terms of the part, the cow heart is only the biggest in the left ventricle. I find that to be somewhat...odd.
We did a lab where we got to cut apart a brain and identify the parts that help to give the brain is funky looking form. For safety reasons we had to use rubber gloves, and an optional goggle accessory. We started off the lab by observing the Dura mater, or outer meanings. though not all the brains had them, the one that we had did. se we wound up cutting of this weird looking white layer from the outside of the brain. After that, we had to identify the cerebrum, where we saw the groves that are known as sulci. you should also see the ridges called gyri, which are pretty close to the medial longitudinal fissure, which separates the left and right hemispheres of the cerebral cortex. We then had a little bit to go and identify nearly every part of the brain. from the thalamus to the central canal, and from the spinal cord to the olfactory bulb.
We wound up getting to cut the brain horizontally. Which is the horizontal way to cut the brain, you just put it on its side, and cut through it. It leaves you with some pepperoni looking slices in your dissection tray. The odd clear stuff on the far left side of the picture is the Dura matter, which is a white "casing" that the brain happens to be in...and its pretty grodi.
Selecting the Notebook tab displays the laboratory protocol in this window. Also, when the main lab window loads another portion of the exercise, appropriate section of the protocol is automatically displayed. Some words show up as hyperlinks like this. That means that more information is available as either a glossary entry or background. Also, each piece of equipment is described in the equipment section.
Objective
Record electrical activities of individual neurons while you deliver mechanical stimulus to the attached skin. Inject flurescent dyes into the neurons to visualize their morphology. Identify the neurons based on the morphology and the response to stimuli, comparing them to previously published results.
Equipment List
Feather: Used to give the leech skin a very gentle touch stimulation. It really doesn't need to be a feather, it could be q-tips or something. Cost: free.
Probe: A blunt metal rod attached to a wooden handle useful for lifting, pushing, pressing, moving of specimen. Here you use it to lift tissue, and to push the skin as a stimulus. Typical price: $1.00 ~ 10.00
Forceps: Fine forceps for very fine manipulations. The very fine ones are known as Dumont #5 forceps, with tip size of about 0.1 mm X 0.06 mm or smaller. Typical price: $15.00 ~ 45.00
Scissors: Good dissecting angled scissors used here to cut open the body wall. Teaching scissors are cheaper, but some ultra-fine dissecting scissors could cost upward of $400, and you better not drop that, because once you drop it, chances are, it's ruined. Typical price: $15.00 ~ 60.00
Pins: Stainless steel dissecting pins for pinning tissue to a dissecting dish or board. You can drop these and not worry about it. $1.00
Scalpel: For microsurgery, disposable scalpel blades are better and much more economical than the fixed blade scalpel which needs to be sharpened periodically. Blade: $0.50 Handle: $10.00 Used here to cut all kinds of things.
Dissection Tray: A tray half-filled with hard wax so that you can stick pins into it to stabilize specimen for dissection.
Leech Tank: Leeches are kept in pond-water (you can actually buy an instant pond-water mix to add to tap water.) If kept in a refrigerator, they can stay happy in it for weeks at a time without feeding.
20% Ethanol: Used to anesthetize the leech. Besides being more humane, it has the added benefit that it stops them from moving, making it easier to pin down the leech.
Leech Tongs: These are basically gross anatomy forceps with blunt tips so that you will not harm the leech as you pick it up. Maybe about $ 10.00
Dissection Microscope: These are binocular microscopes specifically designed for dissection and other micromanipulations. Essentially, it's a high quality high power magnifying glass. The price varies on quality and if you've looked through binoculars of different quality, you can appreciate what a difference good optic makes. On a good one, you can clearly see individual cells in a leech's nervous system. Cost about $1,000.00 ~ $7,000.00
Micromanipulator: A device used to position items with sub-micrometer precision in three dimensions. Here we mount our electrode on it to guide it accurately to a neuron. For work on a leech, a mechanical manipulator would suffice which is about $700.00. More accurate hydraulic or electronic ones may cost up to $10,000.00
Oscilloscope: Basically a sophisticated voltmeter. What you see on the screen is a real time display of voltage (vertical) plotted against time (horizontal). Useful because voltmeters can't track rapidly changing voltages, and even if they could, you couldn't read anything. Cost $2,000.00 and up.
Leech: Medicinal leeches are about $15.00 each. When fully extended, they can reach 15 to 20 cm long. When fully contracted, diameter is roughly 1 ~ 2 cm.
Procedure
Step 1
Catch and anesthetize the leech in 20% ethanol solution. Ethanol is not an anesthetic for vertebrate animals, but can be an effective anesthesia for small creatures that breathe through the skin like the leech. Like in many things, too high a concentration will be harmful or fatal.
Step 2
Pin the animal dorsal side up through the anterior and posterior suckers onto a dissection tray, stretching the animal in the process.
Step 3
Using scissors, make a cut in the skin along the mid-line on the dorsal surface, taking care not to damage deep structures.
Using forceps, carefully tease apart the skin along the cut and pin down the left and right halves of the skin to each side, so that the leech is pinned open with the inside of the skin facing up. This exposes the innards of the leech, including the digestive, excretory and reproductive organs. You cannot see the nervous system yet, because they are located ventrally.
Step 4
Carefully remove the gut and other internal structures to expose the ventrally located nerve cord. The nervous system of the leech is encased within the ventral sinus, which is dark green in color.
Step 5
Notice that there are many swellings up and down the sinus. These contain the segmental ganglia of the nervous system. To make one of them accessible, first we cut a window in the body wall underneath a ganglion, taking care not to damage the nerve cord or any attached nerves in the process.
Step 6
Isolate a section of the animal by making 2 parallel cuts across the animal (perpendicular to theanterior-posterior axis), but sufficently separated so that the strip you remove contains at least oneganglion.
Then, with forceps, flip the piece of skin over so that the outer skin is now face up. Pin the skin down. If you don't know why you are doing this, go read the Why are we doing this? of Step 5 and come back.
Step 7
Cut the sinus with an ultra fine scalpel and using fine forceps, carefully tease apart the sinus to expose the ganglion. Individual cells can now be viewed under the microscope.
In reality, you would only use the scalpel here only if you are extremely good at microdissection. It's very difficult to cut just the sinus without accidentally damaging the ganglion underneath, but hey, we are all perfect in cyberland. Normally, this is done with a pair of very fine forceps.
Click on the electrode to gain control of it. Move the electrode to somewhere over the ganglion then click on the mouse button. This simulates the process of penetrating the cell, which is much more demanding in reality (see "What it's like in reality." for details). Keep your eyes glued to the oscilloscope display while you are doing this. If you find a cell, the display will change. If you see no change, then you have not found a cell. Keep moving your electrode around and clicking until you find a cell. The sound you hear is the oscilloscope display you are seeing fed into an audio amplifier. It provides an audio feedback to what you see on the screen.
Now using a feather, probe or forceps, push around the skin of the animal. Observe if the cell you have penetrated responds to weak (feather), medium (probe), strong (forceps) or any stimulus. Note the pattern of response. The cell may fire action potentials or spikes. The response characteristics will be used when you are comparing your data with published data compiled in the atlas.
When you are satisfied with the electrophysiology, you can start the anatomical investigation by injecting the cell with a fluorescent dye. Push the button labeled "Dye Injection."
Step 9
Next, we will visualize the morphology of the neuron from which you have just recorded using afluorescent dye. Having pushed the button labeled "Dye Injection," the amplifier system has passed an electric current from the electrode that resulted in the ejection of Lucifer Yellow from the tip of theelectrode into the intracellular space. Lucifer Yellow will passively spread throughout the cell after a while. Now you can turn on ultraviolet (UV) light by pushing "UV Switch.". Lucifer Yellow fluoresces bright yellow-green under UV and you will be able to visualize the cell in question, including its axon, dendrites, cell body and so on.
Step 10
You now have electrophysiological data and neuroanatomical data from your experiment. Try to identify the cell based on published data (Atlas) There are many cells in different locations of this ganglion. Repeat the whole procedure for as many cells as you would like.
In this lab, you get to dissect a virtual leech which between me and you, it definitely interesting. It is a very interesting thing, and you learn a lot. Especially considering that you get to basically, electrocute the leech. Though it is a little bit difficult to navigate around their website, it is still a good learning experience.
^^ If you follow the link, there is an article i found about how doctors have now found a new way to treat brain aneurysms using a newly FDA approved pipeline stent. The article is pretty much about a girl named faith who had a brain aneurysm that doctors couldnt get to through normal procedures, and the pipline stent completely saved her life. She says in the article that everry day she is gettting stronger, and feeling better. As for the pipeline stent, it is used by inserting the stent into a persons leg. The stent then starts to expand against the walls of the artery, and across the aneurysm, thus cutting of blood flow. The blood that remains in the blocked-off aneurysm then forms a bloodclot, which reduses the chance for the aneurysm to grow, or rupture. With this new, modern advancement in the medical sciences, doctors can now go through a blood vessel and reconstruct an entire section of the body. The aneurysm will completely heal around the stent, and go away. Although, as of right now, the stent is only FDA approved for certain types of aneurysms, and reduces the recovery time for patients from 6 monthes, to 10 days. If you want to know more about Stents, then visit the site to the right. --> http://www.ivanhoe.com/channels/p_channelstory.cfm?storyid=28549
We did a lab to see how many millivolts a jaw would generate while one eats food. We tried different kinds of food, including bananas, carrots, celery, Gatorade (considered a food now) marshmallow, and pop tarts. As you can tell from the chart, bananas obviously are the hardest to chew, or just simply generate a lot of energy. Which completely disproves my theory of a hard food generating more energy than a soft food. Although i didn't think that Gatorade would generate more energy than a carrot. The marshmallow was pretty close to the same as the pop tart. Although it was a fun time eating and socializing while having electroid tabs attached to your face. These tabs were attached to a probe, which then measures the amount of energy (in mV) generated while you are eating, by your jaw.
Something that you should know about bones, is that they have no blood vessels or nerves. That doesn't mean that they won't hurt if you break one though. You're bones are surrounded by the perichondrium that resists outward expansion. There are 3 different types of skeletal cartilage, Hyline, Elastic, and Fibrocartilage. The Hyline Cartilage is the mot abundant skeletal cartilage, and provides support, flexibility, and resilience to your bones. It is present in Articular (covers the ends of long bones), Costal (connects the ribs to the sternum), respiratory (Makes up larynx and reinforces air passages) and nasal (supports the nose) cartilage. The Elastic Cartilage is similar to the Hyaline cartilage but contains elastic fibers and is found in the external ear and the epiglottis. Fibrocartilage is a cartilage that is highly compressed and has great tensile strength. it contains collagen fibers and is found in the menisci of the knee, and in intervertebral discs.
You may no have known, but your cartilage actually grows. it can grow Appositional and/or Interstitial. Appositional is where cells of the perichondrium secrete matrix against the external face of existing cartilage. If it were to grow interstitial, then the lacunae-bound chondrocytes inside the cartilage would divide and secrete new matrix, expanding the cartilage from within. There is something interesting that happens with the bones during a certain time, called calcification. It occurs during normal bone growth, and during old age. Calcification is the process in which calcium salts build up in soft tissue, making it harden into bone.
There are a couple of ways to classify bones in the human body, Axial, and Appendicular. The Axial bones consist of the skull, vertebral column, and rib cage. Whereas the Appendicular bones consists of the upper and lower limbs, shoulders, and hips. You could also classify bones by their shape, such as the long bone, which is any bone that is longer than it is wide, such as your humerus (bone under bicep). Then there is the opposite of that, which is the short bone, which has to be cube-shaped (wrists and ankles), or be a bone that has formed inside of a tendon (patella). There is also the flat bone, which are bones that are thin, flat and a bit curved (sternum, most skulls). There are also the Irregular bones, which are bones that have a complicated shape (hip bones and vertebrae).
Bones help people in many different ways. they help to support the body by providing a framework that supports the whole body, and cradles the softer organs. It helps to protect the brain, spinal cord, and other vital organs, which simultaneously providing levers for muscles creating an easier way to move for humans. Bones also store minerals, especially calcium and phosphorus, but they also help with blood cell formations. Seeing as how hematopoiesis occur within the marrow cavities of the bones. So, bones are a vital part of our body, without bones, we could look more like jello...There are some bones that have "markings," such as bulges, depressions, and holes that serve as areas where muscles, ligaments, and tendons can attach themselves. They also might have joint surfaces, and Conduits for blood vessels and nerves. We have named some of the areas where muscles and ligaments attach themselves. These would be Tuberosity, Crest, Trochanter, and Line. The Tuberosity is a rounded projections, and the crest is a narrow, prominent ridge of the bone. Whereas the line is just the narrow ridge of the bone. The trochanter is a large, blunt, irregular surface in the bone. There is also the Tubercle, Epicondyle, Spine, and Process. The Tubercle is a small rounded projection, and the Epicondyle is a raised area above the condyle. The Spine is with sharp, slender projections, and the process is and bones prominence. That brings us to the Head, Facet, Condyle, and Ramus. The head is a bony expansion carried on a narrow neck, and the facet is a smooth, nearly flat articular surface. The Condyle (below the Epicondyle) is rounded auricular projections, and the Ramus is the armlike bar of the bone. There are approximately six depressions and openings in the body. There is the Meatus (canal-like passageway), the Sinus (cavity within a bone), the Fossa (shallow, basin like depression), a Groove (furrow), a fissure (narrow, slit-like opening), and the legendary Foramen (A round or oval opening through a bone). Out of all these holes and stuff in the body, you tend to wonder what exactly the texture of it is. Well, there is the compact bone, which is the dense outer layer, which is smooth. Then there is the Spongy bone, which is like a honeycomb of Trabeculae filled with yellow bone marrow. The long bones consist of diaphysis and an epiphysis. The diaphysis is a Tubular shaft that forms the axis of long bones, composed of compact bones that surround the medullary cavity. There is some below bone marrow (fat) that is contained in the medullary cavity. The Epiphysis is the expanded ends of long bones, and its exterior is compact bone, whereas the interior is spongey bone. Its join surface is covered with articular (hyaline) cartilage. The Epiphyseal line separates the diaphysis from the epiphysis.
Included with the bones, is the bone membranes, which have the Periosteum and the endosteum. The Perosteum is a double-layered protective membrane, which is an outer fibrous layer which is a dense regular connective tissue. Its inner osteogenic layer is composed of osteoblasts and osteoclasts. As well as being supplied with nerve fibers, blood, and lymphatic vessels, which enter the one via nutrient foramina. The perosteum is secured to underlying bone to Sharpey's fibers. Endosteum is a delicate membrane curing internal surfaces of bone. The Structure of irregular and flat bones include the thin plates of periosteum is covered by compact bone on the outside with endosteum, which is covered by spongy bone on the inside. It has no diaphysis or epiphysis, although it does contain bone marrow between the trabeculae. Hematopoietic tissue (red marrow) an be found in all people of all ages. In infants it is found in the medullary cavity, and in all areas of spongy bone. In adults it is found in the diplo of flat bones, and the head of the femur and humerus. In the structure of bone, the compact bone has the Haversian system, or the osteon, which is the structural unit of compact bone. There is also the Lamella (weight-bearing, column-like matrix tubes composed mainly of collagen), the Haversian or central canal (central channel containing blood vessels and nerves), and Volkmann's canal (channels lying at right canals to the central canal, connecting blood and nerve supply of the periosteum to that of the haversian canal. There are also Osteocytes (mature bone cells), the Lacunae (small cavities in bone that contain osteocytes), and Canaliculi (hairlike canals that connect lacunae to each other and the central canal). The organic chemical composition of bones include the Osteoblasts (bone-forming cells), Osteocytes (mature bone cells), Osteoclasts (large cells that resorb or break down bone matrix), and Osteoid (unmineralized bone matrix composed of proteoglycans, glycoprotiens, and collagen). As for the inorganic compostiion of bone, there are Hydroxyapatites, or mineral salts. They make up sixty-five percent of bone by mass and are made of primarily calcium phosphates. It is also responsible for bone hardness and resistance to compression. The process of bone tissue formation is known as Osteogeness and ossification. They lead to the formation of the bony skeletons in embryos, along with bone thickness, remodeling of the bones, and bone repairs. They help the bones grow until early childhood. The Formation of the boney skeleton, begins at week 8 of embryo development. it includes Intramembranous ossification (bone develops from a fibrous membrane) and Endochondral ossification (bone forms by replacing hyaline carilage). Intramembranous Ossification is the formation of most of the flat bones of the skull and the clavicles. It also has fibrous connective tissue membranes are formed by mesenchymal cells, and has an ossification center appears in the fibrous connective tissue membrane. Bone matrices are sevreted within the fibrous membrane, and is where woven bone and perosteum form. The bone collar of compact bone forms, and red marrow appears. There are some stages of intramembranous ossification, it starts out with an ossification center appearing in the fibrous connective tissue membrane. Bone matrix is then secreted within the fibrous membrane, and woven bone and the periosteum forms. The Bone collar of compact bone forms, and red marrow appears. Now, its time for Endochondral Ossification.
Endochondral ossification begins in the second month of development, and it uses hyaline cartilage "bones" as models for bone construction. It even requires breakdown of hyaline cartilage prior to ossification. The ossification involves the formation of bone collar, cavitation of the hyaline cartilage, and invasion of internal cavities by the periosteal bud and spongy formation. It also includes the formation of the medullary cavity (appearance of secondary ossification centers in the epiphyses), and the ossification of the epiphyses, with hyaline cartilage remaining only in the epiphyseal plates.
In postnatal bone growth, long bones grow in length and cartilage on the side of the epiphyseal plate closest to the epiphysis is relatively inactive. Cartilage abetting the shaft of the bone organizes into a pattern that allows fast, efficient growth and cells of the epiphyseal plate proximal to the resting cartilage form three functionally different zones: growth, transformation, and osteogenic. The functional zones of the long bones include the growth zone (catilage cells undergo mitosis, pushing the epiphysis away from the diaphysis), transformation zone (older cells enlarge, the matrix becomes calcified, cartilage cells die, and the matrix begins to deteriorate), and the osteogenic zone (new bone formation). The long bone grown in length because the cartilage continually grows and is replaced by bone as shown, and is remodeled when bone is resorbed and aded by appositional growth as shown. As for the hormone regulation of bone growth during a persons youth, it is mainly during infancy and childhood, the epiphyseal plate activity is stimulated by growth hormones. During puberty, there is a lot of testosterone and estrogen that is released, which is initially promoting adolescent growth spurts. They cause masculinization, and feminization of specific parts of the skeleton. They also later induce epiphyseal plate closure, ending the longitudinal bone growth. As for remodeling the units of the bone, includes the adjacent osteoblasts and osteoclasts deposit and resorb bone at periosteal and endsteal surfaces. Which brings us to bone deposition, which occurs where the bone is injured or added strength is needed and requires a diet rich in protein, vitamins C, D, and A, calcium, phosphorus, magnesium, and manganese. Many alkaline phosphate is essential for mineralization of bone, and the location of new matrix depositions are shown by the osteoid seam (unmineralized band of bone matrix) and calcification fronts (abrupt transition zone between osteoid seam and the older mineralized bone).
Sometimes the bones do interesting things, such as Resorption (process where the osteoclasts break down bone to release minerals resulting in the transfer of calcium from bone fluid to the blood). This process of resorption is done by osteoclasts. They use these things called resorption bays (grooves formed by osteoclasts as they brea down bone matrix), and involve the secretion of Lysosomal enzymes that digest organic matrix and acids that convert calcium salts into soluble form, both of which come from the osteoclasts. The dissolved matrix is transcytosed across the osteoclasts cell where it is secreted into the interstitial fluid and then into the blood, such is the process of resorption. Which then leads us to why exactly calcium is so important in our bodies. Well, for starters, it helps the transmission of nerve impulses, controls muscle contractions, helps the blood coagulation, secretes by glands and nerve cells, and helps when it comes to cell division. When it comes to the remodeling of the bones, it is up to two control loops regulating the bones remodeling process. The hormonal mechanism maintains calcium homeostasis in the blood, while mechanical and gravitational forces acting on the skeleton help to remodel the bones. The hormonal mechanism consists of rising blood Ca2+ levels trigger the thyroid to release calcitonin. Calcitonin stimulates calcium salt deposit in bone, where falling blood Ca2+ levels signal the parathyroid glands to release PTH. PTH signals osteoclasts to degrade bone matrix and release Ca2+ into the blood. According to Wolff's law, a bone grows or remodels in response to the forces or demands placed upon it. The observations supporting Wolff's law include long bones are thickest midway along the shaft, where bending stress is greatest. Also, curved bones are thickest where they are most likely to buckle. The trabeculae form along lines of stress, large. bony projections occur where heavy, active muscles are attached.
Bone fractures and breaks are pretty common among the human race for some...odd reason? They are classified by the position of the bone ends after fracture, the completeness of the break, the orientation of the bone to the long axis, and whether or not the bones end penetrates the skin. There are a few different types of bone fractures, which are; non-displaced, displaced, complete, incomplete, linear, transverse, compound, simple, comminuted, spiral, depressed, compression, epiphyseal, and Greenstick. Non-displaced fractures consist of bone ends retaining their normal position. Displaced fractures have the bone ends out of their normal alignment, whereas a complete fracture is broken all the way through. An incomplete fracture is not broken all the way through, and Linear fractures are parallel to the long axis of the bone. Transverse is when the fracture is perpendicular to the long axis of the bone, and the compound (open) is when the bone ends penetrate the skin. Simple (closed) is when the bone ends don't penetrate the skin. A comminuted fracture is when the bone is fragmented into three or more pieces; common injury of the elderly. A spiral fracture is a raged break where the bone is excessively twisted; common sports injury. When the bon is broken into portions thats are pressed inward its a Depressed fracture, which is also a typical skull fracture. Compression breaks are when the bone is crushed; common is porous bones. The epiphyseal fracture is where the epiphysis separates from diaphysis along epiphyseal line, occurs where cartilage cells are dying, and Greenstick is an incomplete fracture where one side of the bone breaks and the other side bends; common in children. By now, you are probably wondering how exactly a bone is healed after it breaks or fractures.
Well, when a bone heals, it started with the bony callus formation, where new bone trabeclae appear in fibrocartilaginous callus. That fibrocartilaginous callus converse into a bone (hard) callus, then it begins a 3-4 week journey after injury, and continues until firm union is form 2-3 months later. Bone remodeling is then done, where excess material on the bone shaft exterior and in the medullary canal is removed, and compact bone is laid down to reconstruct shaft walls. A homeostatic imbalance occurs and the osteomalacia goes to work. Bones are inadequately mineralized causing soft, weakened bones. The main symptom is pain when weight is put on the affected bone. Osteomalacia is caused by insufficient calcium in the diet, or by vitamin D deficiency. Next come the Rickets, where bones of children are inadequately mineralized casing soft weak bones. Bowed legs and deformities of the pelvis, skull, and rib cage common. They are all caused by insufficient calcium in the diet, or by vitamin D deficiency. Osteoporosis, is a pretty well-known disease where the bone reabsorption outpaces bone deposit. The spongy bone of the spine is most vulnerable, although it does occur most often in post menopausal women. Bones become so fragile that sneezing or stepping off a curb can cause fractures. The treatment for osteoporosis consists of calcium and vitamin D supplements, increased weight-bearing exercised, hormone (strogen) replacement therapy (HRT) to slow bone loss, natural progesterone cream prompts new bone growth, and statins increase bone mineral density. Pagets disease is characterized by excessive bone formation and breakdown. Pagetic bone with an excessively high ratio of woven to compact bone is formed, and a reduction of mineralization causes spotty weakening of the bone. Osteoclast activity wanes, but osteoblast activity continues to work. Pagets disease is usually localized in the spine, pelvis, femur, and skill. There is no known causes for Pagets disease and the treatment includes the drugs didronate and fosamax.
In the developmental aspects of bones, the mesoderm gives rise to embryonic mesenchymal cells, which produce membranes and cartilages that form the embryonic skeleton. The embryonic skeleton ossifies in a predictable timetable that allows fetal age to be easily determined from sonograms. At birth, most long bones are well ossifies (except for their epiphyses). By age 25, nearly all bones are completely ossifies, and in old age, bone resorption predominates. A single gene that codes for vitamin d docking determines both the tendency to accumulate bone mass early in life, and the risk for osteoporosis later in life.
As we all know, your bones are not super strength, and as such break a lot. The video to the left shows many people breaking bones simply by trying to catch themselves with their hands.
When we are talking about skin, there are about 3 different layers, or Sections. They are the Epidermis, Dermis, and Hypodermic. The epidermis is the outermost superficial region Of the skin. The dermis is the middle region, and the Hypodermic is the deepest region of the skin. As shown below...
The epidermis is made up of Keratinized squamous epithelial, that can then be divided into four different cell types (Keratinocytes, Melanocytes, Merkel cells, and Langerhans cells). Keratinocytes produce the fibrous protein keratin. Melanocytes produce the brown pigment melanin. Langerhans' cells produce the Epidermal macrophages that help activate the immune system. Merkel cells act as touch receptors in association with sensory nerve endings. there are a few layers of the Epidermis, including the Basal layer. it is the Deepest layer of the Epidermis and is attached to the Dermis. It consists of a single layer of the youngest keratinocytes, which undergo a rapid division and that alternate its name (stratum germinativum). There is also the Stratum Spinosum (prickly layer), where Melanin granules and Langerhans' cells are running free! Each cell contains a web like system of intermediate filaments attached to the Desmosomes. Next we have the Stratum granulosum (granular layer), which has 3-5 thin cell layers where changes of keratinocyte's appearance occur. An Accumulation of keratohyaline and lamellated Granules happens in the cells of this layer. On to the next layer, formally knows as stratum lucidum (clear layer). This layer is made up of flat rows of dead keratinocytes cells. This layer is a transparent band to the granular layer. The final layer of the epidermis is the stratum cornium (horny layer). This layer is known more commonly as the outside of your skin. This layer accounts for 3/4 of the epidermal thickness. It also helps to waterproof the body, and protects from abrasions and penetrations. It even renders the body relatively insensitive to biological, chemical, and physical assaults on the body. That is it for the Epidermis layer...YAY!! Time for the Dermis...muahahahaha. The Dermis is the 2nd major skin region which contains strong, but flexible connective tissue. The cells in this payer consist of Fibroblasts, macrophages, and a few mast cells and white blood cells. It has 2 main layers, the papillary and reticular. The Papillary layer has Areolar connective tissue with collagen and elastic fibers. It has a superior surface that contains peg like projections called dermal papillae. That dermal papillae contains capillary loops, Meisser's corpuscles, and free nerve endings. Whereas the Reticular Layer accounts for approximately 80% of the thickness of skin, Collagen fibers make this possible because they add strength and resiliency to the skin. Elastic fibers provide the stretch-recoil effect on your skin. Thus ending our nice little chat about the Dermis...The Hypodermis is a Subcutaneous layer deep inside the skin, composed of adipose and areolar connective tissue.
All these skin layers help to define what "race" you are, due to a few things located in the skin. Melanin, which shifts from yellow, to reddish-brown, to black. It is associated with darker skin colors, meaning the darker your skin, the more melanin is located inside you. Freckles and pigmented moles are a result from little melanin "pockets" on your face...or wherever your freckles and pigmented moles are. There's Carotene, which is yellow and orange pigmentation of the skin. Carotene is most seen on the palms of your hands, and the soles of your feet. Now it is Hemoglobin, which turns people red, or gives you the pinkish "blush" color. It doesn't make you blush, it just makes you look pinkish. Blushing comes from a rush of blood to your face when you get embarrassed. Although there may be a differentiation in skin colors, there is one thing that almost all people in the world have in common, and that would be sweat glands. There are different types of sweat glands, such as the eccrine sweat glands, the Apocrine sweat glands, the ceruminous glands, and the mammary glands. The Eccrine sweat glands are located on your palms, soles of your feet, and your forehead. The Apocrine sweat glands are found in axillary and anogenital areas of the body. The Ceruminous gland is like a modified apocrine gland that is located in the external ear canal and secrete cerumen (ear wax). The mammary glands are specially made sweat glands that secrete milk. The Sebaceous glands (didn't mention above) is a simple alveolar gland that is found all over the body, and it soften your skins when it is stimulated by hormones. Occasionally it will secrete an oily substance called Sebum. Those are some somewhat positive things about the skin, and now the sad and depressing one, cancer.
There are 3 major forms of cancer that occur on your skin, Basal cell carcinoma, squamous cell carcinoma, and melanoma. The basal Cell Carcinoma is the least malignant and the most common of skin cancers. It's cells proliferate and invade the dermis and hyposermis, slowly growing and don't really metastasize. This type of cancer is cured via surgery in about 99% of skin cancer cases. The Squamous cell Carcinoma comes from the Keatinocytes of the stratum spinosum, and are most often on the scalp, ears, and lower lips. It will grow rapidly if it isn't removed quickly, and will metasize if not removed. The prognosis is good if treated by radiation therapy, but cutting it out works to. Preferably letting a surgeon cut it out...unless you know what your doing of course. Melanoma is the cancer of melanocytes and is the most dangerous of all the skin cancers. Seeing as how it is highly metastatic and chemotherapy doesn't work on it, it makes it extremely difficult to find some sort of cure. There are ways of identifying this cancer, using the ABCD rule. A: Asymmetry; the 2 sides of the pigmented area do not match. B: Border is irregular and exhibits indentations. C: Color (pigmented area) is black, brown, tan, and sometimes red or blue. D: diameter is larger that 6mm (size of a pencil eraser). Melanoma is normally treated by surgery with a side of immunotherapy, although the chance of survival is poor is the melanoma is over 4mm thick. Those are only 3 of the main cancers.
Time for some of the scariest kinds of injuries of the skin, Burns. There are 3 degrees of being burned, first, second, and third. In a first-degree burn, only the epidermis is damage, although it is accompanied by redness, swelling, and some pain. A second-degree burn on the other hand, damages the epidermis and the upper regions of the dermis. They include the symptoms of a first-degree burn, but they have blisters. In a third-degree burn, the entire thickness of the skin is damaged, and the burned area appears gray-white, cherry red, or black. There is no initial edema or pain, because it had destroyed whatever nerve endings were in the burned area. Doctors use the "rule of nines" in order to estimate the severity of ones burns. If over 25% of the body is covered in second-degree burns, then it is considered critical. If over 10% of the body is covered in third-degree burns, then that is critical. Although if there are third-degree burns on your face, hands, or feet, they automatically consider that critical. http://www.youtube.com/watch?v=CJt7XySKqYI <--This link will take you to a video that explains how to treat a second and third-degree burn. That would be skin, stay tuned for hair!!
