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Date Created: 09/12/15
Bio 162 Final Review First exam Blood 0 Blood is a specialized form of connective tissue 0 Cellular parts include RBC WBC and platelets O The extra cellular part is a liquid called plasma Red blood cells 0 The RBC contains 250 million molecules of hemoglobin hg 0 Hg can carry either C02 or 02 0 The RBC can live about 100 days 0 There are about 4 to 5 million RBC per 111 0 Heme group carbon nitrogen iron group molecule where we attach oxygen or carbon dioxide 0 RBC formation hemoerythroblast gt proerythroblast gt basophilic erythroblast gt polychromatophilic erythroblast gt normoblast gt ejection of nucleus amp gt reticulocyte gt enters circulation mature red blood cell Bilirubin 0 When the RBC dies the RBC is removed from the blood and recycled The only part of the recycled RBC that can not be recycled is part of the heme group The carbon nitrogen parts of the molecule is very toxic and must excreted out of the body The spleen creates 90 and the liver creates 10 of bilirubin Indirect bilirubin unconjugated White blood cells 0 WBC are used to fight infection within the body 0 The normal WBC count is between 5000 to 10000 per 111 0 There are five different types each with its own role and the ratio between the five types is often critically important 0 Agranular lymphocytes monocytes O Granular basophils neutrophils eosinophil 0 Order from greatest to least I Neutrophils lymphocytes monocytes eosinophil basophils Neutrophils phagocytic cell often attacking bacteria elevated often during bacterial infection an immature neutrophil is often called a B and cell Lymphocytes soldier of the immune system often seen during a viral infection 0 Monocytes large phagocytic cell in the CT it is often called a macrophage Eosinophil cell is phagocytic against allergic agents and produces proteins against parasitic worms Basophils produces and releases histamine and heparin both are important for in ammation process Blood plasma chemical parts 0 Makes up 55 of the blood Blood clotting 0 Important to prevent the excessive loss of blood 0 Two parts of blood clotting 0 Activation of the clotting cascade 0 Activation of the platelets I Intrinsic damaged surface I Extrinsic tissue factor trauma Heart flow of the blood via heart 1 The blood returns to the heart from the systemic circuit The blood is low in oxygen and low in blood pressure The blood enters the right atrium via superior inferior vena cava 2 The blood now passes from the right atrium into the right ventricle Then passes into the right ventricle via the tricuspid valve 3rd The right ventricle contacts and pumps the blood out of the right side of the heart via the pulmonary semi lunar valve The blood is now in highpressure travels via pulmonary trunk to the lungs 4th the passes into the lungs and the blood will pick up oxygen while the blood pressure falls The blood now returns to the left atrium via the pulmonary veins 5th the blood now passes from the left atrium into the left ventricle via the bicuspid valve The blood is now rich in oxygen but low in blood pressure 61 the left ventricle now contacts and pumps the blood out of the left side of the heart into the systemic circuit Then passes through the aortic trunk The blood is high in oxygen and high in blood pressure Coronary arteries 0 Right coronary artery starts from right side of the aorta just above the valve 0 Two major branches I Marginal artery I Posterior interventricle artery I Left coronary artery starts from left side of aorta just above valve 0 Two major branches I Anterior interventricle artery I Circum ex artery I Posterior ventricle artery from circum ex O Venous structures I Conorary sinus I Middle cardiac vein Heart conduction system I The conduction system helps to ensure an efficient pumping of blood via the heart p x 1 SA node starts contraction of atriums from the top downwards 2rld AV node picks up signal and transmits it down interventriclar septum 3rd Bundle branches travel to bottom of ventricles 4th Purkinje fibers start ventricular contact from the bottom upward Types of blood vessels 0 The blood vessels are pipes that the blood is pumped through by the heart 0 The average body contains some 50000 miles of blood vessels 0 Three basic types 0 Artery high pressure pipes carrying blood away from the heart 0 Vein low pressure pipes carrying blood toward the heart 0 Capillary most common microscopic vessels that connect the arteries to the veins Site of exchange between the blood and the tissues 0 Capillary types 0 Continuous typical locations fat muscle nervous system most abundant O Fenestrated typical locations intestinal villi endocrine glands kidney glomeruli O Discontinuous typical locations liver bone marrow spleen Capillary exchange 0 The exchange of chemical products between the blood and the cells of the body occur at the level of the capillary 0 Osmosis BCOP passive transport of chemicals passing into the blood water is being pulled because it is attached by another molecule 0 Filtration BHP passive transport of chemicals out of the blood and into the tissues of the body pushing of water exerted pressure 0 P wave depolarization of muscles of atrium atrium is contracting 0 QRS wave depolarization of ventricles 0 T waves repolarization of ventricles 0 NEP BHP BCOP 0 Hydrostatic pressure depends on albumin Second exam Lymphatic system Lymphatic system open passive circulatory system consists of three parts A meandering network of lymphatic vessels Lymph the uid contained in those vessels Lymph nodes that cleanse the lymph as it passes through them Lymph Drainage System Three litersday found Within Lymph vessels Lymph nodes Smallest but most numerous about 500 of lymph organs Range in size from 10mm to 25 mm The filter the lymph uid coming from the body s tissues of immunological agents The uid that leaves the lymph node Will then go to the venous blood Capillaries Lymphatic capillaries are blindended tubes in which adjacent endothelial cells overlap each other forming ap like mini valves Lymph Capillaries they are blindended vessels that start Within the tissues of body The Lymph capillary has pores that can drain large chemicals or objects from the tissue Organs all except the thymus have part in tissue makeup Thymus The Thymus is found in the Anterior Mediastinum It is nonencapsulated lymph organ The Thymus creates Tlymphocytes other words the thymus is Where T lymphocytes become able to defend us against specific pathogens in the immune response no thymus no T cells Important in early years of life as Will get older the Thymus degenerates Thymic Hassall s corpuscles involved in development of T cells imposrtant for preventing autoimmune diseases Spleen The Spleen is the largest Lymph organ It is an encapsulated organ in the upper left quadrant Soft bloodrich size of a fist drainage of 3 liters of uid Red pulp remaining splenic tissue disposing of worn out red blood cells and blood borne pathogens White pulp immune functions of the spleen Spleen s two functions 1 Removes dead RBCs 2 Filters Ag agents from the blood Tonsil The Tonsils guard the pharynx form Bacteria in the food amp water The Tonsil will produce the correct Abs and placed Within the blood Stratified squamous Removed if bacteria in crypt 5 tonsils names depends on he location In ammation The Mast cells in the CT produce and release Histamine and Heparin Prevents the spread of damaging agents to nearby tissues dispose of cell debris and pathogens sets the stage for repair Signs Redness Heat Swelling Pain Sometimes loss of function Triggers for Histamine release 1 Local tissue injury 2 Direct trauma to Mast cells 3 Immune system IgE Ag complex Exudate uid containing clotting factors and antibodies seeps from the blood into the tissue spaces causes local swelling edema and pain water and protein Transudate water Red and warms skin Vasodilation causes heat and redness Immune system Attacking an antigen chemical that provokes the immune system from acting Antigen substance capable of provoking an immune response Typically a large complex molecule like a protein not normally present in the body Antibody protein produces by B cell or by plasma cell Antibodies produced by plasma cells are released into body uids where they attach to antigens causing complement fixation neutralization precipitation or agglutination which mar the antigens for destruction by phagocytes or complement Tsvstem or Cell mediated T Lymphocytes protect us 1 most Viral infections 2 animal cell infections 3 solid tissue tumors 4 organ transplants Active cell is TKiller celluses short range proteins Must go to the infection leave lymphocytes and travel through blood and then go 11 the tissue Kill infected cells protect tissues TKiller cell Produces two types of proteins 1 Lymphotoxin will destroy all DNA amp RNA both Viral amp Human within target cell 2 Perforin will cause Cytolysis of target cell A double kill Bsvstem Antibodv mediated BLymphocytes protect us 1 Bacterial infections 2 Yeast infections 3 Fungal infections 4 Some Viral infections Ni 5 Chemicals penicillin Active cell is Plasma Cell uses longrange proteins Antibody structure The Antibody is a fourchain protein The upper arms of the Ab is the Variable or Ag bonding site The lower part of Ab is the constant portion this part provides the chemical immune work against the Ag The Ab will become active When an Ag With the proper shaped Ag attaches to the variable portion Antibody Antigen complex Neutralization of Ag 1 Detoxify Bacteria toxins 2 Attaches to Viral receptor Immobilization of Bacteria turns off Bacteria agella Agglutination of Bacteria causes bacteriaAb to stick togetherresulting in less targets for Neutrophils to phagocytize Complement Fixation protein chain reaction resulting in the lysis of target cell Enhancement of Phagocytosis by Neutrophils AbAg complex provides chemotaxis signal for incoming attacking neutrophils Antibody families lggz single Y unit found in plasma 1 Longest half life 2 Cross the placenta 3 Fixes complement 4 enhanced phagocytosis M five Y units found in plasma 1 Fixes complement best 2 Agglutination IgA double Y unit found in tears saliva mucus amp milk 1 prevents Bacteria from getting into body IgE single Y unit found in CT 1 IgEAg causes release of Histamine IgD single Y unit found surface of B cell 1 involved in activation of B cell s Primary Immune Response Primary and secondary response Memory attack cells are seen in both The primary immune response of the body to antigen occurs on the first occasion it is encountered Depending on the nature of the antigen and the site of entry this response can take up to 14 days to resolve and leads to the generation of memory cells with a high specificity for the inducing antigen The humoral response mediated by B cells with the help of T cells produces highaffinity and antigenspecific antibodies This is in contrast with the CD8 Tcell response which leads to the generation of large numbers of antigenspecific cells that are capable of directly killing infected cells Antigenspecific CD4 T cells which provide help to B cells in the form of cytokines and other stimulatory factors can also be expanded upon antigenic stimulation The secondary response of both B and T cells is observed following subsequent encounter with the same antigen and is more rapid leading to the activation of previously generated memory cells This has some quantitative and qualitative differences from the primary response Respiratory System This organ system allows us to bring in oxygen and blow off carbon Dioxide gas Simple system that contains a series of blind ended tubes Divisions of respiratory The Respiratory system can be divided into 1 Upper respiratory everything above 1st pair of Ribs 2 Lower respiratoryeverything below 1st pair of Ribs The lungs contain the Air Sacs to absorb the oxygen LEFT lung contains two lobes Right lung contains three lobes Right lung Left lung Heavier Lighter Shorter amp wider due to upward compression by liver Longer amp narrower due to side compression by heart Has oblique amp horizontal transverse fissure Only has oblique fissure Three lobes upper middle and lower Two lobes upper and lower Base more concave by liver compression Base less concave Hilum 2bronchi 2pulmonary arteries and 2 Hilum one bronchus 2pulmonary arteries and 2 pulmonary veins pulmonary veins The Nose Nose is divided into two chambers The Nose is used to clean the air warm the air hydrate the air and to detect different smells Larynx The Larynx is composed mostly of Hyaline Cartilage The Larynx acts as a valve to prevent foodliquids from entering the Trachea aids in making vocal sounds and coughing Trachea The Trachea is about one inch in diameter and will carry the air into and out of the Thorax It will remain open because of a series of C shaped cartilaginous rings The Pseudostratified lining the inside will aid in cleaning the air Pulmonary ventilation Inspiration process to bring new air into lungs by lowering air pressure within the lungs below the pressure in the room Expirationprocess to release old air out of lungs by raising air pressure within the lungs above the pressure in the room Respiratory types Quiet of Resting respiration use of Diaphragm Deep or Forced Respiration use of both the diaphragm and intercostal muscles in movement of ribs Respiratory vs Volume Expiratory reserve volume ERV 1000ml Tidal volume TV 500 ml Inspiratory reserve volume IRV 3300 ml in males 1900 ml in females Respiratory Centers Brain control in Medulla Oblongata Two nerve centers 1 Dorsal Respiratory Group controls diaphragm and intercostal muscles for both Quiet and Deep respiration 2 Ventral Respiratory Group used to control accessory muscle for Deep respiration only Bronchial tree Consists of right and left main bronchi which is subdivide within the lungs to form lobar and segmental bronchi and bronchioles Bronchiolar walls lack cartilage but contain complex layer of smooth muscle Constriction of this muscle impedes expiration Air passageways connecting trachea with alveoli cleans warms and moistens incoming air Alveoli Microscopic chambers at termini of bronchial tree Walls of simple squamous epithelium are underlain by thin basement membrane External surfaces are intimately associated with pulmonary capillaries Main sites of gas exchange Special alveolar cells produce surfactant Reduces surface tension helps prevent lung collapse Gas Laws Boyle s Law pressure verses volume the amount of collisions result in the air pressure a decrease in volume results in higher pressure because there is less room so more collisions Dalton s law partial pressure of gases are related to concentration of each gas in a system Henry s Law relationship between partial pressure of a gas in a gaseous state is equal to the partial pressure of a gas in a liquid state Digestive System 0 The digestive system is an open tube single pass system over 20 feet long 0 The goals of the GI Tract is to O Digest food both mechanically and chemically O Absorb nutrients O Absorb water 0 Do it for a profit in terms of energy used vs energy absorbed and enzymes used 0 The trip starts in the mouth 0 The teeth are needed to cut and grind the food 0 The tongue is used for swallowing and also aids in talking and chewing and taste buds 0 Salivary glands three sets produce a number of items including 0 Amylase starch saliva Lipase lipids saliva although not very active till it reaches the stomach IgA proteins saliva Lysozyme proteins saliva Na Bicarbonate stomach Tripzen proteins pancreas Pepsin proteins stomach 000000 New topics Gross renal system Renal system contains two kidneys removal of water soluble waste maintain water balance removal of urea Two kidneys are located retroperitoneal at the level of 11th and 12th ribs Each kidney is surrounded by a layer of adipose tissue Renal pumping 0 Each kidney is connected to the urinary bladder via the ureter 0 The urinary bladder is the storage of urine that has been produced 0 The urinary bladder is connected to the outside world via the urethra Urine drainage in kidney Nephrons make urine stored in renal pyramid lst collecting duct within the renal pyramid 2 minor calyx 3rd major calyx 4th renal pelvis 5th ureter 6th urinary bladder 7th urethra Nephron parts and functions of each part The nephron is the functional unit of the kidney Each kidney contains one million nephrons The kidneys produce 55 gallons of glomerular filtrate day while the urine released per day is only two liters The nephron is a series of tubes that start within the renal cortex Function the rest of the nephron starting with the proximal convoluted tubule that chemicals and water that the body does not want to lose will reabsorb them back into the blood Tubule prox convoluted reabsorbing glucose amino acids water with salt Tubule loop of henle reabsorbing water and salt countercurrent mech Tubule distal convoluted reabsorbing water and salt Reproductive system Meiosis only occurs in sexual glands Female quality males quantity Male reproduction sperminogenesis Female reproduction oogenesis 1st polar body only has a cell membrane The 2rld oocyte has everything all organelles Male reproductive system parts and functions Testes male gonads lie within the scrotum served by both devisions of the autonomic nervous system from the testes the sperm are delivered to the body exterior through a system of ducts including the epididymis the ductus deferns the ejectulatory duct and the urethra which opens to the outside at the tip of the penis Each plum sized testis approximately 4 cm 15 inches long and 25 cm 1 inch in width and is surrounded by two tunics O Tunica vaginalis outer tunic two layered derived from an out pocketing of the peritoneum O Tunica albuginea deep to the serous layer the fibrous capsule of the testis O Seminiferous tubules where meiosis occurs sperm factories tightly coiled surrounding each seminiferous tubule are three layers of muscle like myoid cells By contracting rhythmically these cells may help to squeeze sperm and testicular uids through the tubules and out of the testes The seminiferous tubules of each lobule converge to form a straight tubule or tubule rectus that conveys sperm into the rete testis O Rete testis a tubular network on the posterior side of the testis from the rete testis sperm leave the testis through the efferent ductules and enter the epididymis which hugs the external testis surface posteriorly The immature sperm pass through the head the body and then move into the tail of the epididymis were they are stored until ejaculation O Interstitial cells Leydig cells lie in the soft connective tissue surrounding the seminiferous tubules these cells produce androgen most importantly testosterone which they secrete into the surrounding interstitial uid Thus the sperm producing and hormoneproducing functions of the testis are carries out by completely different cell populations 0 Testicular arteries long branch from the abdominal aorta superior to the pelvis supply the testes O Testicular veins draining the testes arise from a network called the pampiniform venous plexus that surrounds the portion of each testicular artery within the scrotum like a climbing vine O Spermatic cord where nerve fibers are enclosed along with the blood vessels and lymphatic s in the connective tissue sheath The accessory sex glands which empty their secretions into the ducts during ejaculation are the seminal vesicles prostate and the bulbourethral glands Epididymis cupshaped about 38 inches long most of the epididymis consists of highly coiled duct of the epididymis with and uncoiled length of 6 m 20 feet sperm is ejaculated from the epididymis when a male is sexually stimulated and ejaculated the smooth muscle in the ducts of the epididymis contracts expelling sperm into the next segment of the duct system the ductus deferens Sperm can be stored in the epididymis for several months but if held longer they are eventually phagocytized by epithelial cells of the epididymis This is not a problem for the man as sperm are generated continuously Prostate single doughnut shaped gland about the size of a peach pit It encircles the urethra just inferior to the bladder Enclosed by a thick connective tissue capsule it is made up of 20 to 30 compound tubuloalveolar glands embedded in a mass stoma of the smooth muscle and dense connective tissue The prostatic gland secretion enters the prostatic urethra via several ducts when prostatic smooth muscle contracts during ejaculation It plays a role in activating sperm accounts for up to onethird of the semen volume Bulbourethral glands peasized glands inferior to the prostate They produce a thick clear mucus some of which drains into the spongy urethra and lubricates the glans penis when a man becomes sexually excited Additionally the mucus neutralized traces of acidic urine to the urethre just prior to ejaculation Semen milky white somewhat sticky mixture of sperm testicular uid and accessory gland secretions The liquid provides a transport medium and nutrients and contains chemicals that protect and activate the sperm and facilitate their movements Urethra terminal portion of the male duct system it conveys both urine and semen at different times so it serves both the urinary and reproductive systems 0 Three regions I Prostatic urethra portion surrounding the prostate sperm and seminal uid mix in the ejaculatory duct and enter the prostatic urethra together during ejaculation Seminal gland secretion accounts for some 70 of the volume of semen l Membranous urethra intermediate part in the urogenital diaphragm I Spongy urethra penile which runs through the penis and opens to the outside at the external urethral orifice about 15 cm 6 inches long and accounts for 75 of urethral length Its mucosa contains scattered urethral glands that secrete mucus into the lumen just before ejaculation Seminal vesicle adds sugar fructose to the sperm Ductus deferens carrying away about 45 cm 18 inches long carries sperm from epididymis to the body runs upward as part of the spermatic cord of the epididymis through the inguinal canal to the pelvic cavity 0 Ampulla O Ej aculatory duct enters the prostate and there it empties into the urethra Scrotum is a sac of skin and superficial fascia that hangs outside the abdominopelvic cavity at the root of the penis It is covered with sparse hairs and contains paired oval testes The midline septum divides the scrotum providing a compartment for each testis The scrotum is affected by temperature changes When its cold the testis are pulled closer to the pelvic oor and the warmth of the body wall and the scrotum becomes shorted and heavily wrinkled reducing the surface area and increasing its thickness to reduce heat loss When its warm the scrotal skin is accid and loose to increase the surface area for cooling and the testes hang lover away from the body trunk O Dartos muscle layer of smooth muscle in the superficial fascia wrinkles the scrotal skin 0 Cremaster muscles bands of skeletal muscle that arise from the internal oblique muscles of the trunk elevates the testes Penis copulatory organ designed to deliver sperm into the female reproductive tract The penis and scrotum which hang suspended from the perineum make up the external reproductive structure external genitalia of the male 0 Perineum diamond shaped region located between the pubic symphysis anteriorly the coccyx posteriorly and the ischial tuberosites laterally O Glans penis attached root and a free shaft or body that ends in an enlarged tip 0 Foreskin prepuce skin covering the penis is loose and it slides distally to form a cuff 0 Corpus spongiosum spongy body surround the urethra it expands distally to form the glans and proximally to form the past of the root called the bulb of the penis the bulb is covered externally by the sheet like bulbopongiosus muscle and is secured to the urogenital diaphragm 0 Corpus cavernose cavernous bodies make up most of the penis and are bound by the fibrous tunica albuginea O Crura of the penis proximal ends legs surrounded by an ischiocabernosus muscle and anchors to the pubic arch of the bony pelvis Sperm acrosome used to penetrate the cell membrane theres an inhibiting chemical over acrosome when active allows for reproduction dies to exposure to acidity vaginal canal has a lot of it Cowper s gland produces alkaline solution Female reproductive system parts and functions More complex than that of a male not only must she produce gametes but her body must prepare to nurture a developing fetus for a period of nine months Uterine tubes also called the fallopian tubes or oviducts form the initial part of the female duct system They receive the ovulated oocyte and are the site where fertilization generally occurs Each uterine tube is about 10 cm 4 inches long and extends medially from the region of an ovary to empty into the superlateral region of the uterus via a constricted region called the isthmus The distal end of each uterine tube expands as it curves around the ovary forming the ampulla and fertilization usually occurs in this region The ampulla ends in the infundibulum an open funnel shaped structure bearing ciliated fingerlike projection called fimbriae that drape over the ovary Uterus located in the pelvis anterior to the rectum and posterosuperior to the bladder It is a hollow thickwalled muscular organ that functions to receive retain and nourish a fertilized ovum In a fertile woman who has never been pregnant the uterus is about the size and shape of an inverted pear but is usually somewhat larger in women who have borne children The major portion of the uterus is referred to as the body The round region superior to the entrance of the uterine tubes is the fundus and the slightly narrowed region between the body and the cervix is the isthmus The cervix of the uterus is its narrow neck or outlet which projects into the vagina inferiorly The cavity of the cervix is called the cervical canal communicates with the vagina via the external ox and with the cavity of the uterine body via the internal os Vagina is a thinwalled tube 810 cm 34 inches long It lies between the bladder and the rectum and extends from the cervix to the body exterior The urethra parallels its course anteriorly The vagina provides a passageway for delivery of an infant and for menstrual ow Because it receives the penis and semen during sexual intercourse it is the female organ of copulation The distensible wall of the vagina consists of coats an outer fibroelastic adventitia a smooth muscle muscularis and an inner mucosa marked by transverse ridges or rugaq which stimulate the penis during intercourse O Vulva or pudendum covering 0 Clitoris small protruding structure composed largely of erectile tissue which is homologous to the penis of the male Ovaries female gonads shaped like an almond and about twice as large each ovary is held in place by several ligaments in the fork of the iliac blood vessels with the peritoneal cavity are the primary reproductive organs of a female and like the male testes ovaries serve a dual purpose They produce the gametes ova and sex hormones estrogen and progesterone 0 Internal genitalia ovaries and duct system are mostly located in the pelvic cavity The female accessory ducts from the vicinity of the ovary to the body exterior are the uterine tubes the uterus and the vagina They transport or otherwise serve the needs of the reproduction cells and a developing fetus 0 External genitalia the external organs of the female 0 Ovarian follicles embedded in the highly vascular connective tissue of the ovary cortex tiny saclike structures each follicle consists of an immature egg oocyte I Follicle cells surrounding cells are follicle cells if a single layer is present I Primordial follicle one layer of squamouslike follicle cells surround the oocyte I Primary follicle single layer of cuboidal or columnartype follicle cells enclosing the oocyte I Secondary follicle formed when two or more layers of granulosa cells surround the oocyte I Late secondary follicle results when a small uidfilled spaces appear between the granulosa cells I Tertiary follicle forms when the uidfilled pockets coalesce to form a central uidcavity called the antrum at this stage the follicle extends from the deepest part of the ovarian cortex and bulges from the surface of the ovary and its oocyte sits on the stalk of granulosa cells at one side of the antrum I Corpus luteum yellow body after ovulation the ruptured follicle is transformed into a very different looking glandular structure it eventually degenerates Female cycle structures and hormones I Meiosis the specialized nuclear division that occurs in the testes to produce sperm also occurs in the ovaries I Oogenesis the process when sex cells are produced This process can take years to complete 0 First in the fetal period the oogonia the diploid stem cells of the ovaries multiply rapidly by mitosis and then enter a growth phase and lay in the nutrients reserves Gradually primordial follicles begin to appear as the oogonia are transformed into primary oocytes and become surrounded by a single layer of attened follicle cells The primary oocytes begin the first meiotic division but become stalled late in prophase I and do not complete it By birth a female is presumed to have her lifetime supply of primary oocytes Of the original 7 million oocytes approximately 2 million of them escape programmed death and are already in place in the cortical regions of the immature ovary Since they remain in their state of suspended animation all through childhood the wait is a long one 10 to 14 years at the very least At puberty perhaps 250000 oocytes remain Beginning at this time a small number of primary oocytes are recruited activated each month in a response to an LH surge midcycle However only one is selected each time to continue meiosis I ultimately producing two haploid cells each with 23 replicated chromosomes that are quite dissimilar in size The smaller cell is called the first polar body The larger cell which contains nearly all the cytoplasm of the primary oocytes is the secondary oocyte The events of this first maturation division ensure that the polar body receives almost no cytoplasm or organelles The first polar body may continue its development and undergo meiosis II producing two even smaller polar bodies However in humans the secondary oocyte arrests in metaphase II and it is this cell that is ovulated If an ovulated secondary oocyte is not penetrated by a sperm it simply deteriorates But if sperm penetration does occur the oocyte quickly completes meiosis II yielding one large ovum and a tiny second polar body The union of the egg and sperm nuclei constitutes fertilization The potential end products of oogenesis are three tiny polar bodies nearly devoid of cytoplasm and one large ovum All of these cells are haploid but only the ovum is a functional gamete The unequal cytoplasmic divisions that occur during oogenesis ensure that a fertilized egg has ample nutrients for its siX to sevenday journey to the uterus Lacking nutrientcontaining cytoplasm the polar bodies degenerate and die Since the reproductive life of a female is at most about 40 years from the age 11 to approximately 51 and typically only one ovulation occurs each month fewer than 500 oocytes out of her estimated pubertal potential of 250000 are released during a women s lifetime Perhaps the most striking different between male and female meiosis is the error rate As many as 20 of oocytes but only 3 4 of sperm have the wrong number of chromosomes a situation that often results from failure of the homologues to separate during meiosis It appears that faced with meiotic disruption meiosis in males grinds to a halt but in females it marches on Ovarian cycle the monthly series of events associated with the maturation of an egg It is best described in terms of two consecutive phases The follicular phase is the period of follicle growth typically indicated as lasting from the rst to the fourteenth day of the cycle The luteal phase is the period of corpus luteum activity days 1428 The socalled typical ovarian cycle repeats at intervals of 28 days with ovulation occurring midcycle O 1 JUN Follicular Phase maturation of a primordial follicle occupies the rst half of the cycle and involves several events stages 13 When a primordial follicle is activated by a process directed by the oocyte the squamouselike cells surrounding the primary oocyte grow becoming cuboidal cells and the oocyte enlarges The follicle is now called a primary follicle 1 degree Follicular cells proliferate forming a strati ed epithelium around the oocyte As soon as more than one cell layer is present the follicle is called secondary follicle 2 degree and the follicle cells take on the name granulosa cells A layer of connective tissue condenses around the follicle forming the theca folliculi As the follicle grows the thecal and granulosa cells cooperate to produce estrogens The inner thecal cells produce androgens which the granulosa cells convert to estrogens Clear liquid begins to accumulate between the granulosa cells producing the late secondary follicle The uid between the granulosa cells coalesces to form a large uid lled cavity called the antrum an event that distinguishes the vesicular follicle from the late secondary follicle The primary oocyte complete meiosis l to form the secondary oocyte and rst polar body Ovulation occurs when the ballooning ovary wall ruptures and expels the secondary oocyte still surrounding by its corona radiate into the peritoneal cavity In the ovaries of adult females there are always several follicles at different stages of maturation As a rule one follicle outstrips the others to become the dominant follicle and is at the peak stage of maturation when the hormonal LH stimulus is given for ovulation This attains the greatest FSH sensitivity the quickest The others degenerate and are reabsorbed o The Luteal Phase 7 After ovulation the ruptured follicle collapses and the antrum lls with clotted blood This stage begins to secrete progesterone and some estrogen 8 If pregnancy doesn t occur the corpus luteum starts degenerating in about 10 days and its hormonal output ends In this case all that ultimately remains is a scar called corpus albicans quotwhite bodyquot The last two or three days of the luteal phase when the endometrium is just beginning to erode is sometimes called the luteolytic or ischemic phase On the other hand if the oocyte is fertilized and pregnancy ensues the corpus luteum persists until the placenta is ready to take over its hormonal producing duties in about three months Pituitary effects ovary gt follicle only Estrogen gt corpus colsum regrows uterine linings estrogen and progesterone causes the secretory phase glucose into plans levels decrease vascular insult in the next menstrual cycle HCG prolongs corpus luedium
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