Neuromotor Control and Modeling (Subject) / Prevention and Rehabilitation (Lesson)
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M5
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- What is a tissue? A cellular organizational level intermediate between cells and a complete organ. A tissue is an ensemle of similar cells from the same origin.
- What kind of tissue is bone? A bone is a living, well-organised, vascular form of connective tissue.
- What is the connective tissue composed of? The connective bone tissue consists of living cells which are surrounded by matrix. It is composed of: 1.ground substance (primarily water; also consists of glycosaminoglycans, proteoglycans and glycoproteins->glyco- and glycan- indicate the presence of carbohydrates 2.fibers (Collagen fibers-> containing the protein collagen, Elastic fibers-> containing the protein elastin and Reticular fibers-> also containing collagen) 3.cells (primary cells as well as accessory cells (fat cells, white blood cells, macrophages, mast cells, plasma cells) Differentiating factors: cell and fiber type, and/or relative amounts of them All tissues are derived from one common, embryonic, tissue (fibroblasts, chondroblasts, osteoblasts, hematopoietic stem cells)
- In which two subgroups can a skeleton be divided? 1.Axial skeleton: bones of the skull, vertebral column, ribs and sternum 2.Appendicular skeleton: bones of the upper and lower limbs
- What are different types of connective tissue? Cartilage ›Hyaline cartilage›Elastic cartilage›Fibrocartilage Connective tissue proper ›Loose connective tissue: »Areolar»Adipose»Reticular›Dense connective tissue»Dense regular»Dense irregular Bone (osseous tissue) Blood
- What are the functions of bones? 1.Protection-> mechanical protection for most of the body's internal organs 2.Support-> framework, provides attachement for skeletal muscles 3.Levers-> skeleton assists with movement 4.Mineral storage-> Reservoirs for calcium and phosphorus , minerals are released when needed into the blood 5.Blood cell formation-> Hematopoiesis occurs within the bone marrow of certain bones; develops red blood cells in the bone marrow
- Bones are typically classified according to shape. What are different classifications? Long bones (extremities),flat bones (protection of underlying organs e.g. sternum), sesamoid bones (in some tendons in locations where there is considerable friction, tension& physical stress e.g. patellae), Irregular bones (shapes due to the function they fullfil e.g. vertebrae, Short bones (roughly cube-shaped e.g. wrist bones)
- What are bones composed of? Bones are organs: they are composed of more than one type of tissue Apart from osseous tissue they contain nervous tissue (nerves), cartilage, fibrous connective issue (lining cavities), and muscleand epithelial tissue (in blood vessels) Bone is largely composed of an organic protein, collagen and an inorganic mineral, hydroxyapatite-> mechanical and supportive role in the body
- What is the Wolff's law (bones)? “states that bone responds to the stressesthat are imposed upon it by rearranging itsinitial architecture in the best way to with-stand stress (Porter 2008)
- What is the typically gross structure of a long bone (three parts)? A long bone is typically divided into thre parts: Proximal epiphysis, Diaphysis (middle) and Distal epiphysis
- What is the difference between the gross structure of a typically long bone and a flat bone? A flat bone has no shaft or epiphyses and no marrow cavity (but marrow is present in between trabeculae
- What is the periosteum (bone structure)? The periosteum is the outer fibrous layer consisting of dense irregular connective tissue The Inner layer consists of osteoblasts (bone-forming cells) and osteoclasts (bone-destroying cells). It also contains: nerve fibers, blood vessels, and lympathic vessels Sharpey's fibers secure the periosteum to the bone> Insertion for tendons
- What is the Endosteum (bone structure)? It covers the trebeculua and canals and like the periosteum, it also contains osteoblasts and osteoclasts.
- What kind of bone marrow is when present? Where in adults is medullary cavity present? Where takes blood cell production place? When can yellow marrow convert back to red marrow? At birth, all bone is red marrow (Hematopoietic tissue). With age, more and more of it is converted to the yellow type; only around half of adult bone marrow is red.Adults: medullary cavity contains yellow marrow, and this often extends well into the epiphysis. Blood cell production takes only place in the head of the femur and the humerus. Yellow marrow can convert back to red marrow if a person becomes anemic (low red blood cell count).
- What is the structural unit of compact bone? The structural unit of compact bone is the osteon: - cylinder oriented parallell to long axis of the bone - consists of tubes (or lamellae): containing collagen - central canal contains blood vessels and nerve fibers. Also connects perforating canals (Volkmann's canals)
- What is the bone structure of spongy bone? ›Trabeculae align precisely along lines of stress›Irregularly arranged lamellae, osteocytes, canaliculi›No osteons
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- What is the bone structure on a chemical level? Organic components:-Cells : osteoblasts, osteocytes, osteoclastsosteoblasts, osteocytes, osteoclasts-Osteoid»Ground substance: proteoglycans and glycoproteins»Collagen fibers-Organic components contribute to the flexibility and strength of bone Inorganic components:-Mineral salts, hydroxyapatites, like calcium phosphate»Materialize as salt crystals that surround collagen fibers in the extracellular matrix»Gives bone its exceptional hardness»The reason why bones endure long after death
- What is the Osteogenesis/ossification important for? >Formation of the skeleton in embryos>Postnatal bone growth, until early adulthood>Remodeling and repair
- How can bone grow? Bone cannot grow interstitially (dazwischenliegend). It must grow by apposition. Osteoblasts produce new bone. Osteoclasts absorb bones
- Explain the growth in length of a long bone The region of the epiphyseal plate closest to the epyphisis (distal face) contains resting cartilage cells. The cells of the epiphyseal plate proximal to the resting cartilage area are arranged in three functionally different zones- growth, transformation, and osteogenic. 1.) Growth zone: Cartilage cells undergo mitosis 2.) Transformation zone: Older cells enlarge; matrix becomes calcified; cartillage cells die; matrix becomes deteriorating 3.) Osteogenic zone: New bone formation is occuring
- Is the rate of cartilage growth and bone growth equal? When do epiphyseal plates disappear? -Rate of cartilage growth and bone growth are equal-Epiphyseal plates disappear at about 18 (females) and 21 (males) years of age
- What is bone homeostasis? ›Bone is a dynamic and active tissue›5-7% of bone mass is recycled weekly›Remodeling and repair
- How does the remodeling in bones occur (two control loops)? Controlled by two control loops:- Negative feedback loop involving hormones»Aims to maintain Ca2+blood levels- Response to mechanical factors
- Describe the hormonal controls of ionic calcium levels in the blood PTH and calcitonin operate in negative feedback control systems that influence each other. - Calcitonon stimulates calcium salt deposit in bone-> falling blood CA2+ levels - Parathyroid glands release parathyroid hormone -> Osteoclasts degrade bone matrix and release CA2+ into blood-> Rising blood CA2+ levels
- Explain the influence of mechanical factors on the remodeling of bone Wolff’s Law: a bone grows or remodels in response to the forces or demands placedon it (Mechanical loading, Muscle pull and gravity). In other words: a bone's anatomy reflects the common stresses it encounters Important observations:›Long bones are thickest midway along the shaft, exactly where bending forces are greatest›Curved bones are thickest where they are most likely to buckle›Trabeculae of spongy bone form trusses or struts along lines of compression›Large, bony projections occur where heavy, active muscles attach›If bones are not stressed (fetus, bedridden people), bones will not have such prominent features
- Tendon and ligaments are both composed of so called dense regular connective tissue a)When is some structure referred to as a tendon, and when is it referred to as a ligament? b) Name a factor that has a negative influence on the repair capacity of tendons and ligaments as well as on that of cartilage a)Tendon connects muscle to boneLigament connects bone to bone b) Avascularity, i.e. lack of blood vessels
- Two muscles that can be found in the human thigh are the m. sartoriusand the m. rectus femoris a) Which of these two muscles is best suited for generating force, and which can produce the largest motion? Force: m. rectus femoris Motion: m. sartorius b) Motivate your answer. The physiological cro ss - sectional area is greatest in m. rectus femoris, due to the muscle architecture : in pennate muscles, more fibers can be packed in parallel, resulting in the ability to generate la rger forces The m. sartorius is much longer and has a parallel muscle architecture, meaning, there are many muscle fibers positioned in series, rather than in parallel. Many fibers in series allow for a greater shortening, and thus greater movement a) Force: m. rectus femorisMotion: m. sartorius b) The physiological cross-sectional area is greatest in m.rectus femoris, due to the muscle architecture: in pennate muscles, more fibers can be packed in parallel, resulting the ability to generate larger forces. The m. sartorius is much longer and has a prallel muscle architecture, meaning, there are many muscle fibers positioned in series, rather than in parallel. Many fibers in series allow for a greater shortening, and thus greater movement.
- Is the following statement true or false? “The force that a muscle produces during a maximal isometric contraction is the highest force a muscle can generate” False
- Consider the person showing off her m. biceps to some admirers. Use correct anatomical terminology to describe the configuration of the following joints, relative to the anatomical position. More than one answer might be required. a) Elbow (lower arm relative to upper arm) b) Glenohumeral joint (upper arm relative to trunk) c) Wrist (hand relative to lower arm) a) Flexed b)Abducted&exorotated c)(palmar)flexed
- Consider the series of photos of a person walking down stairs. The following question concerns the right leg only. During the descent, the right ankle joint flexes (see photos 2 to 3). Which muscle or muscle group are most likely to control this ankle flexion, the m. soleus/m. gastrocnemius or their antagonist, the m. tibialis anterior? Motivate your answer M. soleus/gastrocnemius. The external moment (due to gravity)in the ankle joint is dorsiflexion.If a static position was to be maintained, we would require an internal moment (caused by activation of muscle tissue) of plantarflexion. This could be delivered by the soleus and/or gastrocnemius. In the present case, where a movement under the influence of gravity is carried out, those muscles are active by means of an eccentric contraction, thus allowing dorsiflexion to occur in a controlled manner.