Bone is the type of connective tissue that forms the body s supporting framework, the skeleton. Serve to protect the internal organs from injury. The bone marrow inside the bones is the body's major producer of both red and white blood cells.
      The bones of women are generally lighter than those of men, while children's bones are more resilient than those of adults Bones also respond to certain physical physiological changes: atrophy, or waste away.
      Bones are generally classified in two ways. When classified on the basis of their shape, they fall into four categories: flat bones, such as the ribs; long bones, such as the thigh bone; short bones, such as the wrist bones; and irregular bones, such as the vertebrae. When classified on the basis of how they develop, bones are divided into two groups: endochondral bones and intramembraneous bones. Endochondral bones, such as the long bones and the bones at the base of the skull, develop from cartilage tissue Intramembraneous bones, such as the flat bones of the roof of the skull, are not formed from cartilage but develop under or within a connective tissue membrane. Although endochondral bones and intramembraneous bones form in different ways, they have the same structure.
      The formation of bone tissue (ossification) begins early in embryological development. The bones reach their full size when the person is about 25.
      Most adult bone is composed of two types of tissue: anouter layer of compact bone and an inner layer of spongy bone. Compact bone is strong and dense. Spongy bone is light and porous and contains bone marrow The amount of each type of tissue varies in different bones. The flat bones of the skull consist almost entirely of compact bone, with very little spongy tissue. In a long bone, such as the thigh bone, the shaft, called the diaphysis, is made up largely of compact bone. While the ends, called epyphyses, consist mostly of spongy bone. In a long bone, marrow is also present inside the shaft, in a cavity called the medullary cavity.
      Surrounding every bone, except at the surface where it meets another bone, is a fibrous membrane called the periosteum. The outer layer of the periosteum consists of a network of densely packed collagen fibres and blood vessels. This layer serves for the attachment of tendons, ligaments, and muscles to the bone and is also important in bone repair.
      The inner layer of the periosteum has many fibres, called fibres of Sharpey, which penetrate the bone tissue, anchoring the periosteum to the bone. The inner layer also has many bone-forming cells, or osteoblasts, which are responsible for the bone's growth in diameter and the production of new bone tissue in cases of fracture, infection.
      In addition to the periosteum, all bones have another membrane, the endosteum. It lines the marrow cavity as well as the smaller cavities within the bone. This membrane, like the inner layer of the periosteum, contains os-teoblasts, and is important in the formation of new bone tissue.

      Bone tissue consists largely of a hard substance called the matrix. Embedded in the matrix are the bone cells, or osteocytes. Bone matrix consists of both organic and inorganic materials. The organic portion is made up chiefly of collagen fibres. The inorganic portion of matrix constitutes about two thirds of a bone's total weight. The chief inorganic substance is calcium phosphate, which is responsible for the bone's hardness. If the organic portion were burned out the bone would crumble under the slightest pressure. In the formation of intramembraneous bone, certain cells of the embryonic connective tissue congregate in the area where the bone is to form. Small blood vessels soon invade the area, and the cells, which have clustered in strands, undergo certain changes to become osteoblasts. The cells then begin secreting collagen fibers and an intercellular substance. This substance, together with the collagen fibers and the connective tissue fibers already present, is called osteoid. Osteoid is very soft and flexible, but as mineral salts are deposited it becomes hard matrix. The formation of endochondral bone is preceded by the formation of a cartilaginous structure similar in shape to the resulting bone. In a long bone, ossification begins in the area that becomes the center of the shaft. In this area, cartilage cells become osteoblasts and start forming bone tissue This process spreads toward either end of the bone. The only areas where cartilage is not soon replaced by bone tissue are the regions where the shaft joins the two epiphyses. These areas, called epiphyseal pla-res, are responsible for the bones continuing growth in length. The bone's growth in diameter is due to the addition of layers of bone around the outside of the shaft As they are formed, layers of bone on the inside of the shaft are removed. In all bones, the matrix is arranged in layers called lamellae. In compact bone, the lamellae are arranged concentrically around blood vessels, and the space containing each blood vessel is called a Haver-sian canal. The osteocytes are located between the lamellae, and the canaliculi containing their cellular extensions connect with the Haversian canals, allowing the passage of nutrients and other materials between the cells and the blood vessels. Bone tissue contains also many smaller blood vessels that extend from the periosteum and enter the bone through small openings. In long bones there is an additional blood supply, the nutrient artery, which represents the chief blood supply to the marrow. The structure of spongy is similar to that of compact bone. However, there are fewer Haversian canals, and the lamellae are arranged in a less regular fashion, forming spicules and strands known as trabeculae.

New words

      bone – кость
      internal – внешний
      phosphorus – фосфор
      atrophy – атрофия
      spongy – губчатый
      tendon – сухожилие
      ligament – связка
      flexible – гибкий
      periosteum – надкостница
      osteoblast – остеобласт (клетка, образующая кость)
      rigidity – неподвижность
      shape – форма
      to crumble – крошиться
      to congregate – собираться
      epiphyseal – относящийся к эпифизу
      shaft – ствол, тело (длинной) кости, диафиз

      Bones of the skull: the neurocranium (the portion of the skull that surrounds and protects the brain) or the viscerocra-nium (i. e., the skeleton of the face). Bones of the neurocranium Frontal, Parietal, Temporal, Occipital, Ethmoid, Sphenoid.
      Bones of the viscerocranium (surface): Maxilla, Nasal, Zygomatic, Mandible. Bones of the viscerocranium (deep): Ethmoid, Sphenoid, Vomer, Lacrimal, Palatine, Inferior nasal concha. Articulations: Most skull bones meet at immovable joints called sutures. The coronal suture is between the frontal and the parietal bones The sagittal suture is between two parietal bones. The lambdoid suture is between the parietal and the occipital bones. The bregma is the point at which the coronal suture intersects the sagittal suture
      The lambda is the point at which the sagittal suture intersects the lambdoid suture. The pterion is the point on the lateral aspect of the skull where the greater wing of the sphenoid, parietal, frontal, and temporal bones converge. The temporomandibular joint is between the mandibular fossa of the temporal bone and the condylar process of the mandible.
      The parotid gland is the largest of the salivary glands. Structures found within the substance of this gland include the following: Motor branches of the facial nerve CN VII enters the parotid gland after emerging from the stylomastoid foramen at the base of the skull. Superficial temporal artery and vein. The artery is a terminal branch of the external carotid artery.
      Retromandibular vein, which is formed from the maxillary and superficial temporal veins.
      Great auricular nerve, which is a cutaneous branch of the cer vical plexus. Auriculotemporal nerve, which is a sensory branch of V3. It supplies the TMJ and conveys postganglionic parasympathetic fibers from the otic ganglion to the parotid gland Parotid (Stensen s) duct, which enters the oral cavity at the level of the maxillary second molar. The facial artery
      is a branch of the external carotid artery in the neck. It
      terminates as the angular artery near the bridge of the nose.

The muscles of face

New words

      brain – мозг
      frontal – лобная
      parietal – теменная
      temporal – височная
      occipital – затылочная
      ethmoid – решетчатая
      maxilla – верхняя челюсть
      zygomatic – скуловой
      mandible – нижняя челюсть
      sphenoid – клиновидная
      vomer – сошник
      lacrimal – слезная
      palatine – небная
      nasal concha – носовая раковина

      Cervical vertebrae: There are seven cervical vertebrae of which the first two are atypical. All cervical vertebrae have the foramina transversaria which produce a canal that transmits the vertbral artery and vein.
      Atlas: This is the first cervical vertebra (C1). It has no body and leaves a space to accommodate the dens of the second cervical vertebra. Axis: This is the second cervical vertebra (C2). It has odontoid process, which articulates with the atlas as a pivot joint. Hyoid bone is a small U-shaped bone, which is suspended by muscles and ligaments at the level of vertebra C3.
      Laryngeal prominence is formed by the lamina of the thyroid cartilage.
      Cricoid cartilage. The arch of the cricoid is palpable below the thyroid cartilage and superior to the first tracheal ring (vertebral level C6). Triangles of the neck: The neck is divided into a posterior and an arterior triangle by the sternocleidomastoid muscle. These triangles are subdivided by smaller muscles into six smaller triangles. Posterior triangle is bound by the sternocleidomastoid, the clavicle, and the trapezius. Occipital triangle is located above the inferior belly of the omohyoid muscle. Its contents include the following: CN XI Cutaneous branches of the cervical plexus are the lesser occipital, great auricular, transverse cervical, and supaclavicular nerves.
      Subclavian (omoclavicular, supraclavicular) triangle is located below the inferior belly of the omohyoid. Its contents include the following: Brachial plexus supraclavicular portion The branches include the dorsal scapular, long thoracic, subclavius, and suprascapular nerves.
      The third part of the subclavian artery enters the subclavian triangle.
      The subclavian vein passes superficial to scalenus anterior muscle. It receives the external jugular vein.
      Anterior triangle is bound by the sternocleidomastoid muse the midline of the neck, and the inferior border of the body of the mandible. Muscular triangle is bound by the sternocleidomastoid muscle, the superior belly of the omohyoid muscle, and the midline of the neck. Carotid (vascular) triangle is bound by the sternocleidomastoid muscle, the superior belly of the omohyoid muscle and the posterior belly of the digastric muscle. The carotid triangle contains the following: Internal jugular vein; Common carotid artery, bifurcates and form the internal and external carotid arteries. The external carotid artery has six branches (i. e., the superior thyroid; the ascending pharyngeal, the lingual, the facial, the occipital, and the posterior auricular arteries). Vagus nerve; hypoglossal nerve; internal and external laryngeal branches of the superior laryngeal branch of the vagus nerve. Digastric (sub-mandibular) triangle is bound by the anterior and posterior bellies of the digastric muscle and the inferi or border of the body of the mandible. It contains the submandibular salivary gland. Submental triangle is bound by the anterior belly of the digastric muscle, the hyoid bone, and the midline of the neck. It contains the submental lymph nodes.

      Root of neck: This area communicates with the superior medi astinum through the thoracic inlet. Structures of the region include the following: subclavian artery and vein. The subclavian artery passes poste rior to the scalenus anterior muscle, and the vein passes ante rior to it Branches of the artery include: vertebral artery; thyrocervical trunk, which gives rise to the inferior thyroid, the transverse cervical, and the suprascapular arteries; Internal thoracic artery.
      Phrenic nerve is a branch of the cervical plexus, which arises from C3, C4, and C5. It is the sole motor nerve to the diaphragm. It crosses the anterior scalene muscle from lateral to medial to enter the thoracic inlet.
      Recurrent laryngeal nerve is a branch of the vagus nerve. This mixed nerve conveys sensory information from the laryngeal; mucosa below the level of the vocal folds and provides motor innervation to all the intrinsic muscles of the larynx except the cricothyroid muscle.
      Thoracic duct terminates at the junction of the left subclavian and the left internal jugular veins On the right side of the body, the right lymphatic duct terminates in a similar fashion.
      Fascias of the neck Superficial investing fascia encloses the platysma, a muscle of facial expression, which has migrated to the neck
      Deep investing fascia surrounds the trapezius and ster-noclei – domastoid muscles.
      Retropharyngeal (visceral) fascia surrounds the pharynx.
      Prevertebral fascia invests the prevertebral muscles of the nee (i. e., longus colli, longus capitis) This layer gives rise to a derivative known as the alar fascia.
      The major muscle groups and their innervations. A simple method of organizing the muscles of the neck is based on two basic principles: (1) The muscles may be arranged in group according to their functions; and (2) all muscles in a group share common innervation with one exception in each group.
      Group 1: Muscles of the tongue. All intrinsic muscles plus all but one of the extrinsic muscles (i. e., those containing the suffix, glossus) of the tongue are supplied by CN XII. The one exception is palatoglossus, which is supplied by CN X.
      Group 2: Muscles of the larynx. All but one of the intrinsic muscles of the larynx are supplied by the recurrent la-ryngeal branch of the vagus nerve. The sole exception is the cricothyroid muscle, which is supplied by the external laryngeal branch of the vagus.
      Group 3: Muscles of the pharynx. All but one of the longitudinal and circular muscles of the pharynx are supplied by CNs X and XI (cranial portion). The sole exception is the stylopharyngeus muscle, which is supplied by CN IX.
      Group 4: Muscles of the soft palate. All but one of the muscles of the palate are supplied by CNs X and XI (cranial portion). The sole exception is the tensor veli palatini, which is supplied CN V3.
      Group 5: Infrahyoid muscles. All but one of the infrahyo-id muscles are supplied by the ansa cervicalis of the cervical olexus (C1, C2, and C3). The exception is the thy-rohyoid, which is supplied by a branch of C1. (This branch of C1 also supplies the geniohyoid muscle).

New words

      neck – шея
      cervical – цервикальный
      vertebrae – позвоночник
      cricoid cartilage – перстневидный хрящ гортани
      scapulae – лопатка
      scalene – лестничная мышца
      brachial plexus – плечевое сплетение
      vagus nerve – блуждающий нерв
      hypoglossal nerve – подъязычный нерв
      laryngeal branches – гортанные ветви

      There are 12 thoracic vertebrae. Each rib articulates with the body of the numerically corresponding vertebra and the one below it. Sternum: the manubrium articulates with the clavicle and the first rib. It meets the body of the sternum at the sternal angel an important clinical landmark.
      The body articulates directly with ribs 2–7; it articulates interiorly with the xiphoid process.
      Ribs and costal cartilages: there are 12 pairs of ribs, which are attached posteriorly to thoracic vertebrae.
      Ribs 1–7 attach directly to the sternum by costal cartilages.
      Ribs 8 – 10 attach to the costal cartilage of the rib above. Ribs 11 and 12 have no anterior attachments. The costal groove is located along the inferior border of each rib and provides protection for the intercostal nerve artery, and vein.
      There are 11 pairs of external intercostal muscles.
      These muscles fill the intercostal spaces from the tubercles of ribs posteriorly to the costochondral junctions anteriorly. There are 11 pairs of internal intercostal muscles.
      These muscles fill the intercostal spaces anteriorly from the sternum to the angles of the ribs posteriorly.
      Innermost intercostal muscles: the deep layers of the internal intercostal muscles are the innermost intercostal muscles.
      Subcostalis portion: Fibers extend from the inner surface of the angle of one rib to the rib that is inferior to it.
      Internal thoracic vessels, branches of the subclavian arteries, run anterior to these fibers. Intercostal structures
      Intercostal nerves: there are 12 pairs of thoracic nerves, 11 intercostal pairs, and 1 subcostal pair.
      Intercostal nerves are the ventral primary rami of thoracic spinal nerves. These nerves supply the skin and musculature of the thoracic and abdominal walls.
      Intercostal arteries: there are 12 pairs of posterior and anterior arteries, 11 intercostal pairs, and 1 subcostal pair.
      Anterior intercostal arteries.
      Pairs 1–6 are derived from the internal thoracic arteries.
      Pairs 7–9 are derived from the musculophrenic arteries.
      Posterior intercostal arteries: the first two pairs arise from the superior intercostal artery, a branch of the costo-cervical trunk of the subcla vian artery.
      Nine pairs of intercostal and one pair of subcostal arter ies arise from the thoracic aorta.
      Intercostal veins: Anterior branches of the intercostal veins drain to the internal thoracic and musculophrenic veins.
      Posterior branches drain to the azygos system of veins.
      Lymphatic drainage of intercostal spaces: anterior drainage is to the internal thoracic (parasternal) nodes.
      Posterior drainage is to the paraaortic nodes of the poste rior mediastinum.

New words

      thoracic – грудной
      wall – стенка
      clavicle – ключица
      xiphisternal – грудинный
      groove – углубление
      intercostal – межреберный
      subcostal – подкостный
      transversus – поперечный
      musculophrenic – мышечный грудобрюшной
      paraaortic – парааортальный
      mediastinum – средостение

      Blood is considered a modified type of connective tissue Mesodermal is composed of cells and cell frag ments (erythrocytes, leukocytes, platelets), fibrous proteins (fibrinogen), and an extracellular fluid and proteins (plasma). It also contains cellular elements of the immune system as well as humoral factors
      The formed elements of the blood include erythrocytes, leukocytes, and platelets.
      Erythrocytes, or red blood cells, are important in trans porting oxygen from the lungs to tissues and in returning carbon dioxide to the lungs. Oxygen and carbon dioxide carried in the RBC combine with hemoglobin to form oxyhemoglobin and carbaminohemoglobin, respectively.
      Mature erythrocytes are denucleated, biconcave disks with a diameter of 7–8 mm. The biconcave shape results in a 20–30 % increase in sur face area compared to a sphere.
      Erythrocytes have a very large surface area: volume ratio that allows for efficient gas transfer. Erythrocyte membranes are remarkably pliable, enabling the cells to squeeze through the narrowest capillaries In sickle cell anemia, this plasticity is lost, and the subsequent clogging of capillaries leads to sickle crisis. The normal concentration of erythrocytes in blood is 3,5–5,5 million/mm 3 in women and 4,3–5,9 million/mm 3in men. The packed volume of blood cells per total volume of known as the hematocrit. Normal hematocrit values are 46 % for women and 41–53 % for men.
      When aging RBCs develop subtle changes, macrophages in the bone marrow, spleen, and liver engulf and digest them. The iron is carried by transferring in the blood to certain tissues, where it combines with apoferritin to form ferritin. The heme is catabolized into biliver-din, which is converted to bilirubin. The latter is secreted with bile salts.
      Platelets (thromboplastids) are 2–3 mm in diameter.
      They are a nuclear, membrane-bound cellular fragments derived by cytoplasmic fragmentation of giant cells, called megakaryocytes, in the bone marrow.
      They have a short life span of approximately 10 days.
      There are normally 150 000–400 000 platelets per mm3 of blood. Ultrastructurally, platelets contain two portions: a peripheral, light-staining hyalomere that sends out fine cytoplasmic processes, and a central, dark-staining granulomere that con tains mitochondria, vacuoles, glycogen granules, and granules. Platelets seal minute breaks in blood vessels and maintain endothelial integrity by adhering to the damaged vessel in a process known as platelet aggregation. Platelets are able to form a plug at the rupture site of a vessel because their mem brane permits them to agglutinate and adhere to surfaces.
      Platelets aggregate to set up the cascade of enzymatic reac tions that convert fibrinogen into the fibrin fibers that make up the clot.

New words

      mesodermal – мезодермальный
      erythrocytes – эритроциты
      platelets – тромбоциты
      carbon – углерод
      dioxid – диоксид
      span – промежуток
      light-staining – легкое окрашивание
      to aggregate – соединяться

      Leukocytes, or white blood cells, are primarily with the cellular and humoral defense of the organism foreign materials. Leukocytes are classified as granulocytes (neutrophils, eosinophils, basophils) and agranulocytes (lympmonocytes).
      Granulocytes are named according to the staining properties of their specific granules. Neutrophils sare 10–16 mm in diameter.
      They have 3–5 nuclear lobes and contain azurophilic granules (lysosomes), which contain hydrolytic enzymes for bacterial destruction, in their cytoplasm. Neutrophils are phagocytes that are drawn (chemotaxis) to bacterial chemoattractants. They are the primary cells involved in the acute inflammatory response and represent 54–62 % of leukocytes.
      Eosinophils: they have a bilobed nucleus and possess acid granulations in their cytoplasm. These granules contain hydrolytic enzymes and peroxidase, which a discharged into phagocytic vacuoles.
      Eosinophils are more numerous in the blood during allergic diseases; they norma asent only – 3 % of leukocytes.
      Basophils: they possess large spheroid granules, which are basophilic and metachromatic
      Basophils degranulate in certain immune reaction, releasing heparin and histamine into their surroundings They also release additional vasoactive amines and slow reacting substance of anaphylaxis (SRS-A) consisting of leu-kotrienes LTC4, LTD4, and LTE4. They represent less than 1 % – of leukocytes
      Agranulocytes are named according to their lack of specific granules. Lymphocytes are generally small cells measuring 7 – 10 mm in diameter and constitute 25–33 % of , leukocytes. They con tain circular dark-stained nuclei and scanty clear blue cyto plasm. Circulating lymphocytes enter the blood from the lymphatic tissues. Two principal types of immunocompetent lymphocytes can be identified T lymphocytes and В lymphocytes.
      T cells differentiate in the thymus and then circulate in the peripheral blood, where they are the principal effec tors of cell-mediated immunity. They also function as helper and suppressor cells, by modulating the immune response through their effect on В cells, plasma cells, macrophages, and other T Cells.
      В cells differentiate in bone marrow. Once activated by contact with an antigen, they differentiate into plasma cells, which synthesize antibodies that are secreted into the blood, intercellular fluid, and lymph. В lymphocytes also give rise to memory cells, which differentiate into plas ma cells only after the second exposure to the antigen. Monocytes vary in diameter from 15–18 mm and are the largest of the peripheral blood cells. They constitute 3–7 % of leukocytes.
      Monocytes possess an eccentric nucleus. The cytoplasm has a ground-glass appearance and fine azurophilic granules.
      Monocytes are the precursors for members of the mo-nonuclear phagocyte system, including tissue macrophages (histiocytes), osteoclasts, alveolar macrophages, and Kupffer cells of the liver.

New words

      mesodermal – мезодермальный
      erythrocytes – эритроциты
      leukocytes – лейкоциты
      fibrous proteins – волокнистые белки
      immune – иммунный
      humoral – гуморальный
      to contain – содержать
      nuclei – ядра

      Plasma is the extracellular component of blood. It is an aqueous solution containing proteins, inorganic salts, and organic com pounds Albumin is the major plasma protein that maintains the osmotic pressure of blood. Other plasma proteins include the globulins (alpha, beta, gamma) and fibrinogen, which is necessary for the formation of fibrin in the final step of blood coagulation Plasma is in equilibrium with tissue interstitial fluid through capil lary walls; therefore, the composition of plasma may be used to judge the mean composition of the extracellular fluids Large blood proteins remain in the intravascular compartment and do not equilibrate with the interstitial fluid Serum is a clear yellow fluid that is separated from the coagulum during the process of blood clot formation. It has the same com position as plasma, but lacks the clotting factors (especially fib rinogen).
       Lymphatic vessels
      Lymphatic vessels consist of a, fine network of thin-walled vessels that drain into progressively larger and progressively thicker-walled collecting trunks. These ultimately drain, via the thoracic duct and right lymphatic duct, into the left and right subclavian veins at their angles of junction with the internal jugular veins, respectively. The lymphatics serve as a one-way (i. e., toward the heart) drainage sys tem for the return of tissue fluid and other diffusible substances, including plasma proteins, which constantly escape from the blood through capillaries. They are also important in serving as a conduit for channeling lymphocytes and antibodies produced in lymph nodes into the blood circulation.
      Lymphatic capillaries consist of vessels lined with endothelial cells, which begin as blind-ended tubules or saccules in most tis sues of the body Endothelium is attenuated and usually lacks a continuous basal lamina. . Lymphatic vessels of large diameter resemble veins in their struc ture but lack a clear-cut separation between layers. Valves are more numerous in lymphatic vessels. Smooth muscle cells in the media layer engage in rhythmic contraction, pumping lymph toward the venous system. Smooth muscle is well-developed in large lymphatic ducts.
      Circulation of lymph is slower than that of blood, but it is nonetheless an essential process. It has been estimated that in a single day, 50 % or more of the total circulating protein leaves the blood circulation at the capillary level and is recaptured by the lymphatics.
      Distribution of lymphatics is ubiquitous with some notable excep tions, including epithelium, cartilage, bone, central nervous sys tem, and thymus.

New words

      plasma – плазма
      extracellular – внеклеточный
      aqueous – водный
      solution – раствор
      proteins – белки
      inorganic – неорганический
      salts – соли
      organic – органический
      albumin – альбумин
      globulins – глобулины
      alpha – альфа
      beta – бета
      gamma – гамма
      fibrinogen – фибриноген
      lymphatic – лимфатический
      vessel – сосуд
      endothelium – эндотелий
      circulation – кровообращение
      lymph – лимфа
      ubiquitous – вездесущий
      notable – известный

      Hematopoietic tissue is composed of reticular fibers and cells, blood vessels, and sinusoids (thin-walled blood channels). Myeloid, or blood cell-forming tissue, is found in the bone marrow and provides the stem cells that develop into erythrocytes, granulocytes, agranulocytes, and platelets. Red marrow is characterized by active hemato-poiesis; yellow bone marrow is inactive and contains mostly fat cells. In the human adult, hematopoiesis takes place in the mar row of the flat bones of the skull, ribs and sternum, the vertebral column, the pelvis, and the proximal ends of some long bones. Erythropoiesis is the process of RBC formation. Bone marrow stem cells (colony-forming units, CFUs) differentiate into proerythroblasts under the influence of the glycoprotein erythropoietin, which is produced by the kidney.