By T. Owen. Wheaton College, Wheaton Illinois. 2017.

Cerebrospinal fluid is secreted by choroid plexuses in the ventricular walls buy 3 ml lumigan with visa. The fluid circulates through the ventricles and central canal purchase lumigan 3 ml with amex, enters the subarachnoid space, and is reabsorbed into the blood of the dural sinuses through the arachnoid villi. Blood-Brain Barrier compounds (alcohol, for example) pass readily through the BBB. Certain inorganic ions (Ca+ and K+) pass more slowly, so that The blood-brain barrier (BBB) is a structural arrangement of the concentrations of these ions in the brain differ from those in capillaries, surrounding connective tissue, and specialized neu- the blood plasma. Other substances, such as proteins, lipids, crea- roglia called astrocytes (see figs. The BBB must be taken into account when blood to the extracellular fluid of the brain. Nervous Tissue and the © The McGraw−Hill Anatomy, Sixth Edition Coordination Central Nervous System Companies, 2001 384 Unit 5 Integration and Coordination Although the BBB is an important protective device, it is thoracic vertebrae. Nerves emerging from this region serve the essential that the brain be able to monitor and respond to fluctu- upper extremities. The lumbar enlargement lies between the ations in blood glucose, pH, salinity, osmolarity, and pressure. Nerves from the lumbar For this reason, the BBB is absent in limited brain areas, includ- enlargement supply the lower extremities. The embryonic spinal cord develops more slowly than the associated vertebral column; thus, in the adult, the cord does not Knowledge Check extend beyond L1. Where is cerebrospinal fluid produced and where does it level of L1 to the coccyx. The spinal cord develops as 31 segments, each of which gives rise to a pair of spinal nerves that emerge from the spinal cord through the intervertebral foramina. Two grooves, an ante- rior median fissure and a posterior median sulcus, extend the SPINAL CORD length of the spinal cord and partially divide it into right and left portions. Like the brain, the spinal cord is protected by three dis- The spinal cord consists of centrally located gray matter, involved tinct meninges and is cushioned by cerebrospinal fluid. The pia in reflexes, and peripherally located ascending and descending mater contains an extensive vascular network.

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This is the lies deep to the peroneus longus and is positioned closer to the strongest tendon in the body order lumigan 3ml amex, but it is frequently ruptured from Van De Graaff: Human IV generic 3 ml lumigan overnight delivery. Muscular System © The McGraw−Hill Anatomy, Sixth Edition Companies, 2001 284 Unit 4 Support and Movement FIGURE 9. The popliteus muscle two muscles are frequently referred to as a single muscle, the tri- is a medial rotator of the knee joint during locomotion. The soleus and gastrocnemius muscles have a bipennate flexor hallucis longus muscle lies deep to the soleus common insertion, but the soleus acts on only the ankle joint, in muscle on the posterolateral side of the leg. It has a very long, slender ten- soleus, and it parallels the flexor hallucis longus muscle on the don of insertion onto the calcaneus. Its distal tendon passes posterior to the frequently mistaken for a nerve by those dissecting it for the first medial malleolus and continues along the plantar surface of time. The plantaris is a weak muscle, with limited ability to flex the foot, where it branches into four tendinous slips that at- the knee and plantar flex the ankle joint. Muscular System © The McGraw−Hill Anatomy, Sixth Edition Companies, 2001 Chapter 9 Muscular System 285 Muscles of the Foot With the exception of one additional intrinsic muscle, the ex- tensor digitorum brevis (fig. The functions of the muscles of the foot are different, however, because the foot is adapted to provide support while bearing body weight rather than to grasp objects. The muscles function either to move the toes or to support the arches of the foot through their contraction. Because of their complexity, the muscles of the foot will be presented only in il- lustrations (see figs. List all the muscles that either originate from or insert on the scapula. On the basis of function, categorize the muscles of the upper extremity as flexors, extensors, abductors, adduc- tors, or rotators. Which muscles of the lower extremity span two joints, and therefore have two different actions? CLINICAL CONSIDERATIONS Compared to the other systems of the body, the muscular system is extremely durable.

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Vomiting is a reflexive re- The outer serosa completes the wall of the GI tract discount lumigan 3 ml on line. It is a bind- sponse to many toxic chemicals; thus generic 3ml lumigan overnight delivery, even though unpleasant, it ing and protective layer consisting of loose connective tissue cov- can be beneficial. Innervation of the Gastrointestinal Tract The body has several defense mechanisms to protect against The GI tract is innervated by the sympathetic and parasympa- ingested material that may be harmful if absorbed. The acidic environment of the stomach and the lymphatic system kill many thetic divisions of the autonomic nervous system (see fig. A mucous lining throughout the GI tract serves as a The vagus nerves are the source of parasympathetic activity in Van De Graaff: Human VI. Digestive System © The McGraw−Hill Anatomy, Sixth Edition Body Companies, 2001 640 Unit 6 Maintenance of the Body the esophagus, stomach, pancreas, gallbladder, small intestine, and upper portion of the large intestine. The lower portion of the large intestine receives parasympathetic innervation from spinal nerves in the sacral region. The submucosal plexus and myen- teric plexus are the sites where preganglionic neurons synapse Transverse palatine folds with postganglionic neurons that innervate the smooth muscle of of hard palate the GI tract. Stimulation of the parasympathetic neurons in- creases peristalsis and the secretions of the GI tract. Palatine uvula Postganglionic sympathetic fibers pass through the submu- Pharyngo- cosal and myenteric plexuses and innervate the GI tract. The ef- palatine arch fects of sympathetic nerve stimulation are antagonistic to those of parasympathetic nerve stimulation. Sympathetic impulses in- hibit peristalsis, reduce secretions, and constrict muscle sphinc- ters along the GI tract. List the four tunics of the GI tract and identify their major tissue types.

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The remaining haploid nucleus with its 23 chromo- multiple sperm from entering the egg buy generic lumigan 3 ml. Soon after ization is the completion of the second meiotic division of being incorporated into the ooplasm purchase 3ml lumigan fast delivery, the nuclear envelope the egg, which extrudes the second polar body. At this of the sperm disintegrates; the male pronucleus is formed point, the male and female pronuclei unite, followed by ini- and increases 4 to 5 times in size. The two pronuclei, which tiation of the first mitotic cell division (Fig. Contact between the sperm and egg their nuclear membranes, and the pronuclei fuse. The zy- triggers the acrosome reaction, which is required for sperm gote (fertilized egg) then enters the first mitotic division penetration. Sperm proteolytic enzymes are released that (cleavage) producing two unequal sized cells called blas- dissolve the matrices of the cumulus (granulosa) cells sur- tomeres within 24 to 36 hours after fertilization. Develop- rounding the egg, enabling the sperm to move through this ment proceeds with four-cell and eight-cell embryos and a densely packed group of cells. The sperm penetrates the morula, still in the oviduct, forming at approximately 48, 72, zona pellucida, aided by proteolytic enzymes and the and 96 hours, respectively. The morula enters the uterine propulsive force of the tail; this process may take up to 30 cavity at around 4 days after fertilization, and subsequently, minutes. After entering the perivitelline space, the sperm a blastocyst develops at approximately 6 days after fertiliza- CHAPTER 39 Fertilization, Pregnancy, and Fetal Development 687 First polar body Sperm Metaphase spindle A Egg H Spindle of Granulosa first mitotic division (cumulus cells) (cleavage) Zona pellucida B G Perivitelline space Ooplasm C F FIGURE 39. B, Con- tact between the sperm and Second polar body the zona pellucida. The blastocyst implants into the uterine wall on ap- for embryo transport, protection against mechanical dam- proximately day 7 after fertilization. At the 20- to 30-cell stage, a fluid-filled cavity (blasto- coele) appears and enlarges until the embryo becomes a Implantation Requires the Interaction of hollow sphere, the blastocyst.

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