Exam 2 CBIO 2200 STUDY GUIDE
Exam 2 CBIO 2200 STUDY GUIDE CBIO 2200
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This 40 page Study Guide was uploaded by Bailey Dickinson on Sunday September 11, 2016. The Study Guide belongs to CBIO 2200 at 1 MDSS-SGSLM-Langley AFB Advanced Education in General Dentistry 12 Months taught by in Fall 2016. Since its upload, it has received 57 views. For similar materials see Anatomy and Physiology I in Cellular biology at 1 MDSS-SGSLM-Langley AFB Advanced Education in General Dentistry 12 Months.
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CBIO 2200 EXAM 2 STUDY GUIDE “Name one Passive transport process. Describe why this process is passive, and which way substances are moving across the membrane.” • Diffusion of oxygen across the plasma membrane. From higher to lower concentration • Facilitated diffusion is saturable- you have as many places as can be occupied by the substrate. Every protein interacting with a solute molecule- so can’t go any faster because we don’t have any proteins that are waiting for a solute. Tonicity: one solution relative to something else and reference point is the cell interior Osmolarity: a measure of how many particles are present in the solvent Filtration: the flow of liquid through a filter (or membrane that acts like a filter) due to hydrostatic pressure Active transport processes: require energy (provided directly by ATP or energy provided indirectly by another process) One phosphate group getting clipped off of the ATP provides energy. Primary active transport • Hydrolysis of ATP provides energy to drive the mechanism • Usually catalyzed by membrane protein “pumps” • Can result in the formation of a concentration gradient across a membrane • Na+/K+ ATP-ase in an important example 2 K+ are pumped in and 3 Na+ are pumped out. This creates a Cells work really hard to keep sodium out. The ATP phosphorylates the protein pump and the ATP is hydrolyzed (by the up-pump) for that energy to be released. The protein pump is dephosphorylated and the K+ ions dissociate from it. The pump has different affinities for K+ and Na+ depending on its shapes. Electrochemical gradient. The sodium goes into the cell just because it wants to move down its concentration gradient Secondary active transport • ATP is used indirectly • Transport of 2 or more substances that are “coupled” to each other • Movement of one substance “downhill” drives the movement of another substance “uphill” • (Water builds up behind a dam and you can release it to create energy) • We can use it to drive cells out or drive cells in. The energy is coming from the sodium gradient. • Opposite directions (antiport) Same direction (symport) Is the inside of the plasma membrane positive or negative relative to the outside? What role do you think active transport plays in generating this difference in charge? Negative- because the outside is more positive. 3 out and 2 in. Separation of concentration and a separation of charge. Vesicular Transport • Large molecules or particles are brought into the cell • Sacs or vesicles are formed from invaginations of the plasma membrane -Endocytosis -Phagocytosis -Pinocytosis -Exocytosis These only occur in living cells The transport of a molecule is described as: moving down its concentration gradient, rate of transport is saturable (reaches a maximum), energy is NOT required. Facilitated diffusion Digestion in the stomach requires the production of highly concentrated acid (HCl). What transport process do you think is involved in acid production in the stomach? Moving against concentration gradient. Active transport. Actually, secondary active transport. What is an electrochemical gradient (p. 528-529) a) Concentration b) Charge (Side information: Some people respond to some drugs differently because some people have genes that metabolize certain drugs faster than others) Weak hydrogen bonds between strands- can be broken easily The information about the proteins is stored in the nucleotides Protein structure is linked to DNA structure • Proteins are like words- amino acids are letters • DNA is like words- nitrogenous bases are like the letters • 3 BASE TRIPLET = 1 amino acid (3 nitrogenous bases in a particular order code for a specific amino acid) Some amino acids have more than one code for them. Protein synthesis • Proteins dictate the function(s) of the cell • Protein synthesis is directed by genetic information • Genetic information is DNA in the nucleus • DNA à RNA à Protein • We go form DNA to RNA because RNA represents just a section of DNA • RNA can leave the nucleus Protein synthesis includes 2 processes, or steps (transcription and translation) Transcription (in nucleus) is like taking notes in shorthand. DNA à RNA (mRNA) Translation (in cytoplasm) is from RNA à proteins (nucleotide language to the amino acid language) (tRNA) The cytosol is where to protein synthesis machinery is RNA is similar to DNA • Composed of nucleotides -Sugar-phosphate “backbone” with nitrogen-containing bases RNA is different than DNA • Uracil replaces thymine as the nitrogen-containing base • Ribose replaces deoxyribose as the sugar in the “backbone” • RNA is always found as a single strand 3 main kinds of RNA • tRNA (transfer RNA) -Picks up amino acids in the cytosol and brings them to the ribosome for the polypeptide synthesis • rRNA (ribosomal RNA) -Makes up part of the ribosome • mRNA (messenger RNA) -The “copy” of the DNA sequence that travels to the ribosome and directs protein synthesis. “Gets the message”. The mRNA is complementary. The gene is the specific part of the DNA that codes for a specific protein The mRNA strand is complementary to the template strand with Uracil. The mRNA strand is therefore the same as the DNA coding strand with Uracil instead. Translation- mRNA code becomes a protein Translation • Triplet code of the mRNA is converted to the “language” of amino acids • mRNA interacts with other kinds of RNA to build a protein (or strands of amino acidss Introns are spliced out and exons remain. It’s now believed that introns still play a role, we are just not sure what their purpose is Each group of three bases is a codon tRNA has anticodon mRNA has codon The recognition between the anticodon and the codon occurs based on the complementary base pairing The ribosome forms the peptide bonds between the amino acids AUG is start codon P side translates, A site is where the transfer RNA carrying the next amino acid goes, the E site is where the transfer RNA is released. The amino acid polypeptide chain grows out of the P site How is DNA replication similar to transcription? How is translation different to transcription? During DNA replication, 1 nucleotide is deleted from a sequence that normally codes for a polypeptide. What effect will this deletion have on any resulting amino acid sequences? -Frame shift. All of the codes from that one on are messed up. A strand of DNA has the following base sequence ATGGAACTT What is the complementary mRNA strand? UACCUUGAA Codon is on the mRNA and the anticodon is on the tRNA 3 codons are possible in this strand Cell division- Mitosis • Somatic cells divide, producing 2 identical daughter cells • Each daughter cell contains identical genetic instructions • Replication of the genetic instructions ensures that cell characteristics are continuous from generation to generation • Most cells in the body use mitosis (but not sex cells) ‘ Meiosis is for sex cells and is not an identical replication. Mitosis and cell division a) Cell cycle i) Interphase ii) G1 iii) G2 iv) S b) Mitotic phases i) Prophase ii) Metaphase iii) Anaphase iv) Telophase The phases are continuums and not distinctly cut off from one another What process is affected by a lack of RNA polymerase? Transcription How is DNA replication similar to transcription? They both use a template strand to form another strand. Transcription uses RNA polymerase and DNA replication uses DNA polymerase. Both copies are complementary. A single muscle cell can have up to 12 nuclei Glands are derived from epithelium • Glands are one or more cells that make and secrete a particular product (therefore, some glands are single-celled and some glands are multi- cellular • Substances are secreted into ducts, onto surfaces, or into the blood Endocrine vs. Exocrine • Endocrine glands secrete their product [hormones] into the interstitial fluid and from there into the bloodstream • Endocrine glands are DUCTLESS • Most common example of endocrine secretions are hormones The above picture is extra information ^^ Crosstalk happens through these hormones but the stomach/intestines in themselves are not hormones. • Exocrine glands secrete their products into ducts that empty onto a surface or into a lumen • Exocrine glands are DUCTED • Some organs can have both (ex. Pancreas) exocrine- into digestive system endocrine-insulin and glucagon to regulate metabolism and digestive functions Mechanisms of secretion Merocrine- secretions are released via exocytosis into the gland lumen (majority of human glands) Holocrine- cells die and rupture, so secretion includes the secretory product and cell fragments (sebaceous glands. Epithelium regenerates-on going process) Glands respond to hormones and become more active- more pimples Apocrine- controversial! Secretory product and pinched off region from apical region of the cell. (body odor) a) The only thing being released is the secretory product b) Secretory product and apical regions of the cell pinched off Membranes Two types of tissue- epithelial and connective tissue (typically areolar connective) Membranes are simple organs Mucous Membrane (mucosae) • Line body cavities that open to the outside • “Wet” because the surface remains moist, bathed by secretions of the epithelium or some other substance (i.e., urine) Mucus is in places where there needs to be a reduction of friction (in stomach to protect form acid) Serous Membrane • Lines closed body cavities • Simple squamous epithelium (endothelium or mesothelium) on a layer of areolar connective tissue • Double layers (two of each), with a thin layer of serous fluid between • Pleura (around lungs), pericardium (around heart), peritoneum (around digestive organs) Visceral layer- closest to organ Parietal layer- further from organ Serous fluid is in-between Found around organs or structures that are within motion Cutaneous Membrane • Skin! • Covers the body • Keratinized stratified squamous epithelium with a dense irregular connective tissue layer • “dry” membrane, meaning that it’s exposed to air Synovial Membrane • Line synovial joints (do not open to outside) • Not a true membrane because there is no epithelial layer • Synovial fluid lubricated the joint, provides nutrients for cartilage and removes waste No hair, but (yes sweat glands) on thick skin. Thick skin includes the palms of your hands and soles of your feet. Epidermis • Epithelium • Stratified, squamous, keratinized epithelium (keratinized is waterproof) • Many cells in close proximity • Distinct cell layers Cells are dying in the stratum granulosum Thick skin has stratum lucidum in between corneum and granulosum, in addition to the other 4 layers of the epidermis Stratum corneum is composed of little flat dead cells of keratin There are live cells in the basale, spinosum. Cells undergoing mitosis are in basale (also where melanin is) The cells closer to the surface are dying because of loss of nutrients (no blood supply) Stratum spinosum gets its name from the word spidery • Epidermis – Outer Layer; Keratinized stratified squamous epithelium • Dermis – Second layer underneath epidermis; dense irregular connective tissue • Hypodermis – Deep integumentary layer; loose connective tissue The vast majority of cells are: keratinocytes Melanocytes are also important because they produce a pigment: melanin. They have long projections that squeeze between nearby cells. The pigment is taken in by other keratinocytes. The melanin absorbs and protects against UV radiation. The melanin comes form melanocytes but is incorporated into other cells. Melanin is placed on top of the cell, not underneath. Langerhan’s cells- long spiky projections that go in between the keratinocytes- encounter microbial invaders. It engulfs it and then alerts the immune system Merkel cells- sensory cells in stratum basale that detect touch (activate sensory nerve ending) (intraepidermal receptor ends- another name) Skin from thin to thick: abdomen, shoulder, palm 1. What is a tissue? A group of cells that share a similar structure and function 2. Epithelial Tissue a) Characteristics b) Classification i. By cell shape ii. By arrangement into layers c) Simple Epithelia i. Simple squamous ii. Simple cuboidal iii. Simple columnar 1) Ciliated vs. non-ciliated Non-ciliated- line most of the digestive tract Ciliated- line very small bronchi and uterine tubes iv. Pseudostratified columnar d) Stratified Epithelia i. Stratified squamous ii. Stratified cuboidal iii. Stratified columnar iv. Transitional epithelium e) Glandular epithelium i. Endocrine glands vs. exocrine glands ii. Single-celled glands vs. multicellular glands iii. Structural classification 1) simple vs. cuboidal 2) alveolar vs. tubular iv. Functional classification (i.e. modes of secretion) We didn’t cover the yellow highlighted information in class. EXAM 2 LEARNING OBJECTIVES Read The Nucleus and DNA Replication (106 -111); Protein Synthesis (112-117); Cell Growth and Division (117-123) The Nucleus • Some cells (muscle cells) contain more than one nucleus (multinucleated) • Some cells (mammalian red blood cells) don’t contain any nuclei at all • Inside the nucleus, DNA is stored • When a cell divides, the DNA must be duplicated • RNA is manufactured in the nucleolus • In the nucleus, there are threads of chromatin composed of DNA and proteins. Along the chromatin , the DNA is wrapped around histone proteins. • A nucleosome is a single, wrapped DNA -histone complex • A chromosome is a condensed form of chromatin Identify and describe the stages DNA replication • Few cells in the body don’t divide (nerve cells, skeletal muscle fibers, and cardiac muscle cells) • DNA molecules are made up of two strands that compliment each other. • DNA consists of covalent (within each linear strand) and hydrogen bonds (between nitrogenous bases) • Parts of DNA: Phosphate group, deoxyribose sugar , nitrogenous bases (Adenine, Thymine, Guanine, Cytosine) • Adenine pairs with Thymine and Guanine pairs with Cytosine • The two new daughter cells each contain one pre -existing strand of DNA, and one newly-synthesized (thus- semiconservative) • Three stages of DNA replication: Initiation, Elongation, Termination Initiation: The complementary strands are unwound and separated by a helicase enzyme, as well as other enzymes Elongation: Each strand is a template. DNA polymerase brings the correct, complementary bases to complete each template strand base by base Termination: Once the two original strands are bound to their own, new complementary strands, DNA replication stops • Mistakes made have the potential to render a gene dysfunctional or useless • Enzymes check the newly synthesized DNA for mistakes, and correct them Identify and describe the stages of protein synthesis • A gene is a functional segment of DNA that provides the genetic information necessary to build a protein • Gene expression, which transforms the information coded in a gene to a final gene product, ultimately dictates the structure and function of a cell by determining which proteins are made. • Proteins are chains of amino acids • Three DNA bases in a row represent a “codon” that code for a specific amino acid • An RNA molecule is the intermediate in the two -step process that turns the DNA code into a protein Transcription: • Transcription is DNAàRNA and takes place within the nucleus • A single strand of mRNA is produced, and that mRNA carries a copy of the genetic code out of the nucleus and into the cytoplasm, where it’s used to produce proteins • The triplets within the gene on a specific part of DNA transcribe the complementary mRNA strand • The mRNA is complementary to the template strand of DNA, but instead of thymine, mRNA uses uracil to bind with adenine. • The mRNA is identical to the coding strand of DNA, with uracil replacing thymine • There are three stages of transcription Initiation: A region at the beginning of the gene called a promoter- a particular sequence of nucleotides- triggers the start of transcription Elongation: RNA polymerase unwinds the DNA segment. RNA polymerase adds new, complementary nucleotides to the growing strand of RNA. The coding strand specifies the amino acid sequence of the encoded protein. The mRNA is complementary to the template strand and identical to the coding strand (but uracil instead of thymine, remember?) Termination: When the RNA polymerase reaches the end of a gene, on triplet (either UAA, UAG, or UGA) codes a “stop” signal, which triggers the enzymes to terminate transcription and release the mRNA. • This mRNA is really a “pre-mRNA” at this stage, because it contains long regions that don’t code for amino acids. Splicing removes these non-coding regions by use of a spliceosome. The segments that are removed are called introns. Exons remain. Some introns that are removed are actually coding, but depending on what’s spliced out, different possibilities of structure and function emerge. Translation: • The process of synthesizing a chain of amino acids called a polypeptide • Requires a “translator”- the molecule that will conduct the translation, and a substrate on which the mRNA strand is translated into a protein • rRNA is RNA that, together with proteins, composes the structure of the ribosome (the substrate on which translation takes place) • Ribosomes consist of both a small and a large subunit, and when translation is ready to occur, the two subunits come together and attach to the mRNA • tRNA (transfer RNA) bring the correct amino acids to the ribosome and attaches them to each other • The tRNA consist of a binding site for a specific amino acid, and on the other side, an “anticodon” that matches the codon on the mRNA • There are three main stages: Initiation: binding of a ribosome to an mRNA transcript Elongation: the recognition of a tRNA anticodon with the next mRNA codon in sequence. Once they’re bound, the tRNA releases its amino acid cargo to the growing polypeptide chain. The attachment requires energy. Termination: the final codon (stop codon) on the mRNA is reached. This signals the termination of translation and release of the newly synthesized protein. A gene within DNA is transcribed into mRNA and the mRNA is then translated into a protein product. Distinguish between interphase and the phases of cell reproduction • One cycle of the cell cycle consists of interphase, followed by mitosis and cytokinesis • Interphase is the period of the cell cycle during which the cell is not dividing. • The majority of cells are in interphase the majority of the time • Mitosis is the division of genetic material, during which the cell nucleus breaks down and two, fully functional nuclei are formed. • Cytokinesis divides the cytoplasm into two distinctive cells (cytokinesis is really part of mitosis) • Interphase has 3 phases: G1, S, and G2 • During the G1 phase, cells carry out normal functions, duplicate organelles, and begin replicating centrosomes • During S, the cell replicates its DNA • During G2, cell growth continues, other enzymes and proteins are synthesized, and centrosome replication is completed. Identify the stages of mitosis and describe each • During the mitotic phase of the cell, a cell undergoes two major processes: mitosis (the contents of the nucleus are equitably pulled apart and distributed between its two halves) and cytokinesis (dividing the cytoplasm and cell body into two new cells) Prophase: chromosomes condense and become visible; spindle fibers emerge from the centrosomes; nuclear envelope breaks down; centrosomes move towards opposite poles Metaphase: chromosomes are lined up at the metaphase plate; each sister chromatid is attached to a spindle fiber originating from the opposite pole Anaphase: centromeres split in two; sister chromatids (now called chromosomes) are pulled toward opposite poles; certain spindle fibers begin to elongate the cell Telophase: chromosomes arrive at opposite poles and begin to decondense; nuclear envelope material surrounds each set of chromosomes; the mitotic spindle breaks down; spindle fibers continue to push poles apart • Chckpoints between each stage determine if the process can continue or if it must be halted Distinguish between mitosis and meiosis: Meiosis has two rounds of genetic separation and cellular division while mitosis only has one of each. In meiosis homologous chromosomes separate leading to daughter cells that are not genetically identical. In mitosis the daughter cells are identical to the parent as well as to each other. Read Types of Tissues (138); Tissue Membranes (141 -142); Epithelial Tissues (142-152); Connective Tissue Supports and Protects (152-161); Muscle Tissue and Motion (162-164); Nervous Tissue Mediates Perception and Response (164 -166) Name the 4 basic tissue types and identify characteristics of each • Epithelial tissue: the sheets of cells that cover exterior surfaces of the body, lines internal cavities and passageway s, and forms certain glands • Connective tissue: binds the cells and organs of the body together and functions in the protection, support, and integration of all parts of the body • Muscle tissue: excitable, responding to stimulation and contracting to provide movement, and occurs as three major types: skeletal, smooth, and cardiac • Nervous tissue: also excitable, allowing the propagation of electrochemical signals in the form of nerve impulses that communicate between different regions of the body Tissue Membranes • Made of epithelial and connective tissue • Connective tissue membranes: -Formed solely form connective tissue -Encapsulate organs such as the kidneys, and line out moveable joints -Synovial membranes are a type of connective tissue membrane that lines the cavity of a freely movable joint (not a true membrane because no epithelial layer) (don’t open to the outside) • Epithelial membranes: -Composed of an epithelium attached to a layer of connective tissue -Mucous membranes are composites of connective and epithelial tissues. Mucous membranes line the body cavities and hollow passageways that open to the external environment and also include the digestive, respiratory, excretory, and reproductive tracts. -Mucus covers the epithelial layer, and the underlying connective tissue layer is called the lamina propria - Serous membranes are epithelial membranes composed of mesothelium that are supported by connective tissue. They don’t open to the outside, and line the coelomis cavities (those that don’t open to the outside), and cover organs within these cavities. Serous fluid lubricates the membrane and reduces friction between organs. Serous membranes are edentified depending on their location. Pericardium - heart Peritoneum-digestive and abdominal organs and Pleura -lungs -Cutaneous membranes- skin. Stratified squamous epithelium that rests on top of dense irregular connective tissue. Describe the general features of epithelial tissue • Highly cellular, with little or no extracellular material present between cells • Adjoining cells form a connection between their cell membranes known as a cell junction • Different types of epithelial cells have different roles, whether they’re facing the surface, or closest to underlying bodily structures (basale) • The basal lamina, a mixture of glycoproteins and collagen, provides an attachment for the epithelium, separating it from the underlying connective tissue. • The basal lamina attaches to a reticular lamina (secreted by the underlying connective tissue), forming a basement membrane • First line of protection form physical, chemical, and biological wear and tear • Cells are replaced constantly Describe the functions of each type of epithelial tissue and identify possible locations Connective Tissue Supports and Protects (152 -161); Muscle Tissue and Motion (162-164); Nervous Tissue Mediates Perception and Response (164-166) Describe glands based on their structure /function • Endocrine glands are ductless and secrete directly into surrounding tissues and fluids (hormones) • Exocrine glands are ducted and open directly, or indirectly, to the external environment (releases into a duct that leads to the epithelial surface) (mucus, sweat, saliva, breast milk) • Exocrine glands are either unicellular or multicellular. The unicellular glands are scattered single cells, such as goblet cells, found in them mucous membranes of the intestine • The multicellular exocrine glands, known as serous glands develop from a simple epithelium to form a secretory surface that secretes directly into an inner cavity Compare and contrast the types of glands present in the skin (sebaceous and sudoriferous) Sebaceous: composed of epithelial cells; found mostly in hair follicles on our body; exerts oily fluids and fatty material called “sebum”; functions are to waterproof the body and lubricate the hair; found on the face, scalp, and potentially all over the body (NOT on palms and soles) Sudoriferous: sweat glands; function is to protect the skin form severe dryness; sweat also deters bacteris from entering the sacs of human skin • Types of secretion: merocrine, apocrine, and holocrine Merocrine: most common. The secretions are enclosed in vesicles that move to the apical surface of the cell where contents are released by exocytosis Apocrine: accumulates near the apical portion of the cell. That portion of the cell and its secretory contents pinch off from the cell and are released. (Sweat glands of armpit) Both merocrine and apocrine continue to produce a nd secrete with little damage to the cell because the nucleus and golgi regions remain intact after secretion Holocrine: the rupture and destruction of the entire gland cell. The cell accumulates its secretory products and releases them only when it bursts (sebaceous glands that product the oils on skin and hair- pimples) Describe the general features of connective tissue and identify different types of connective tissue • Support and connect other tissues • Connective tissue cells are dispersed in a matrix (large amount of extracellular material produced by the connective tissue cells that are embedded within it) • The major component of the matrix is a ground substance often crisscrossed by protein fibers. This ground substance is usually a fluid, but it can also be mineralized and solid, as in bones • The three broad categories of connective tissue are classified according to characteristics of their ground substance and the types of fibers found within the matrix Describe the functions of each type of connective tissue and identify possible locations Connective tissue proper: variety of cell types and protein fibers suspended in a viscous ground substance. Dense connective tissue is reinforced by bundles of fibers that provide tensile strength, elasticity, and protection. Loose connective tissue has fibers that are loosely organized, with large spaces between them. (surrounds blood vessels, provides support to organs, in the dermis, tendons, ligaments) Supportive connective tissue: bone and cartilage- provide strength to the body and protect soft tissues (hyaline cartilage: joints, respiratory tract, immature skeleton) (fibrocartilage: intervertebral discs, spinal cord) (elastic cartilage: epiglottis, outer ear) Fluid connective tissue: lymph and blood- various specialized cells circulate in a watery fluid containing salts, nutrients, and dissolved proteins Types of fibers secreted by fibroblasts in connective tissue: Collagen fiber- made from fibrous protein subunits linked together to form a long and straight fiber Elastic fiber- contains the protein elastin alone with other proteins. After being stretched or compressed, it returns to original shape Reticular fiber- narrow fibers that are arrayed in a branching network Describe the general characteristics of muscle tissue • Characterized by properties that allow movement • They’re excitable (respond to a stimulus) and contractile (they can shorten and generate a pulling force) Describe the general characteristics of nervous tissue • Excitable and capable of sending and receiving electrochemical signals that provide the body with information. • Two main classes of cells make up nervous tissue: Neuron- propagates information via electrochemical impulses, called action potentials, which are biochemically linked to the release of chemical signals Neuroglia- play an essential role in supporting neurons and modulating their information propagation Read Layers of the Skin (181-192); Accessory Structures of the Skin (193-198); Functions of the Integumentary System (198 - 203) Identify the tissue types present in skin (in both epidermis and dermis) Epidermis- stratified squamous epithelium Dermis- dense, irregular connective tissue Describe the layers of the epidermis, and the cells present in each (layers: stratum corneum, stratum granulosum, stratum spinosum, stratum basale) • The epidermis is composed of keratinized, stratified squamous epithelium. It contains no blood vessels. • The cells in all of the layers except the stratum basale are keratinocytes (manufacture and store keratin- keratin has hardness and water resistant properties) The basale layer contains basal cells (cuboidal shaped stem cells) • The cells in the stratum basale bond to the dermis via intertwining collagen fibers (basement membrane) • Cells in the stratum basale and the stratum spinosum are alive. Upper-level cells are dead, because of no blood supply • Other important cells in the epidermis include melanocytes, langerhan’s, and merkel cells Melanocytes: produce melanin pigment. They have long projections that squeeze between nearby cells. The pigment is then taken in by keratinocytes Langerhan’s: long, spiky projections that go inbetween keratinocytes- encounter microbial invaders- engulfs them and then alerts immune system Merkel: sensory cells in stratum basale that detect touch (activate sensory nerve ending) (intraepidermal receptor ends is another name) Describe the functions of each epidermal layer Stratum corneum: exposed to outside environment; 15-30 layers of cells; dry, dead layer; helps prevent the penetration of microbes and the dehydration of underlying tissues; shed periodically and replaced by cells pushing up from stratum granulosum; entire layer is replaced during a period of 4 weeks Stratum lucidum: smooth, seemingly translucent; only found in thick skin of palms, soles, and digits; cells are densely packed; provides a barrier to water Stratum granulosum: 3-5 layers deep; flatter, thickened membranes; generates large amounts of keratin proteins; grainy appearance; cells begin to die here; the nuclei and other cell organelles disintegrate, leaving keratin and cell membranes Stratum spinosum: spiny, because desmosones interlock in this layer and strengthen bonds between cells; 8-10 layers of keratinocytes; includes langerhan’s cells Stratum basale: deepest layer; attaches epidermis to the basal lamina, which is attached to the dermis; wound with dermal papilla projections, which increase strength of con nection to dermis; includes melanocytes and merkel cells Compare thick and thin skin Thick skin (palms and soles) contains another layer of the epidermis (stratum lucidum), which is found between stratum corneum and stratum granulosum Identify the layers of the dermis Papillary: loose, areolar connective tissue; the collagen and elastin fibers form a loose mesh; this layer projects into the dermis with papillae; this layer consists of fibroblasts, fat cells, and a lot of small blood vessels; it also contains defense cells, lymphatic capillaries, nerve fibers, and touch receptors Reticular: much thicker than the papillary layer; dense, irregular connective tissue; rich sensory and sympathetic nerve supply; elastin fibers are present, and collagen fibers provide structure and strength, with strands of collagen extending both into the papillary layer, and the hypodermis; collagen also binds to water to keep the skin hydrated Didn’t get to this information in class. Do not focus on for test, unless it’s included in this Tuesday’s lecture material notes that will be posted under the study guide material as well: Identify at least 4 functions of the skin Describe the keratinization process of epidermal growth Identify the skin appendages Describe the structure of nails Describe the structure of hair Outline the process of tissue repair involved in normal healing of a superficial wound WEEK 6 NOTES (9/13-Exam 2) Another word for Langerhans’s cells (dendritic cells) Stratum lucidum means “the clear layer”: found only in thick skin Dermis • Connective tissue • Papillary region is areolar connective tissue • Reticular region is dense irregular connective tissue Cow-hide (dense irregular connective tissue) very strong and tough in multiple directions Tissue that surrounds the hair is an extension of the epidermis The arrangement of the nipple-like projections of the dermis increases the surface area, functionality, and strength of the skin Appendage Structures • Derivatives of the epidermis (but we find them in the dermis) • Can be sites of disease Shaft vs. hair root Root can actually extend down to the hypodermis Part of hair in the “hair-ball” is called the hair follicle Sebaceous glands are always associated with hair follicles (keeps it functional and keeps it from getting dried out) The arrector pili muscle is also associated with the hair follicle When cats or dogs feel threatened, their hair stands up (protective mechanism) When the hair stands up, it creates a blanket of warm air that’s close to the skin (thermoregulatory mechanism) (you see it when you have goose bumps too) Hair root plexus- nerve ending that curves around the bulb of the hair. Allows you to feel touch when you move the hairs without actually touching the skin. Allows the hairs to serve as a sensory organ. Some hairs grow more quickly than other hairs. Now, zoom in on the hair bulb- in the deepest part of the dermis Dermal papille (extension of the dermis into the hair follicle) is in the middle- where the blood supply is (provides nutrients to the hair cells) (melanin also is one of the pigments that gives hair its color) The cells that are mitotically active are at the hair matrix (the single layer) The growth pattern in hair is similar as it is in the epidermis The cells will eventually die as they get pushed away from the blood supply Protects against UV radiation Keeps things out Inappropriate hair growth: Hircutism A person gets a burn on the forearm that destroys the epidermis and extensive areas of the deep dermis. When the injury heals, will hair grow again in the affected area? No, if the dermis is destroyed, we destroy the follicles and the hair won’t grow back. If just the epidermis is destroyed, then the hair will still grow back because the hair follicle is in the dermis, even though it’s a derivative of the epidermis Nails are more useful for animals then humans Also derivatives of the epithelium (epidermis) Fingernails are similar to hairs because they have a lot of keratin Growth pattern is similar to growth pattern of epidermis and hairs Mitotically active cells are in nail matrix. And they’re pushed out. Glands in the skin (open to epidermis) Sebaceous- oil glands; exocrine; ducted onto hair follicles; mechanism of secretion is holocrine (acne) Sudoriferous- sweat glands -Eccrine -Apocrine Eccrine: Clump of a gland in the dermis, and then a single duct opens Produce normal sweat; releases onto surface of skin to cool; evaporative cooling; Merocrine (exocytosis) Apocrine: The duct of the apocrine sweat gland is associated with the hair follicle; armpit, groin, bearded areas of the face; become more active at puberty; apocrine sweat glands actually don’t secrete their products through apocrine mechanisms (contrary to what we thought long ago)- it’s actually just a merocrine mechanism; the sweat product is different- very attractive to certain kinds of bacteria; this is where body odor comes from Repair of the skin • Regeneration- replacement of damaged tissue with the same kind of tissue • Fibrosis- replacement of damaged tissue with scar tissue Neurons do not regenerate (Parkinson’s disease, Alzheimer’s disease) No blood vessels in the epidermis Superficial healing If cut, we’d see an increase in the rate of mitosis in stratum basale. Individual cells would migrate across the dermis until they bumped into each other. The epidermis is replaced, but there’s not an overgrowth of the epidermis Deep wound healing (where the dermis is involved as well) There is bleeding Repair of the skin • Inflammation • Organization/Proliferation • Regeneration/Fibrosis/Maturation We need to know an overview of what’s happening and compare is to superficial healing In inflammatory stage- vasodilation, cells get bigger and leakier (deliver regenerative factors and white blood cells to the area) The initial tissue- granulation tissue
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