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- Anatomy And Physiology 1 Lecture Notes Pdf
- Anatomy And Physiology 1 Lecture Notes Pdf
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Anatomy And Physiology 1 Lecture Notes Pdf
Bones are an important part of the musculoskeletal system. This article, the first in a two-part series on the skeletal system, reviews the anatomy and physiology of bone. The skeletal system is formed of bones and cartilage, which are connected by ligaments to form a framework for the remainder of the body tissues.
This article, the first in a two-part series on the structure and function of the skeletal system, reviews the anatomy and physiology of bone. Understanding the structure and purpose of the bone allows nurses to understand common pathophysiology and consider the most-appropriate steps to improve musculoskeletal health.
Citation: Walker J Skeletal system 1: the anatomy and physiology of bones. Nursing Times [online]; 2, The skeletal system is composed of bones and cartilage connected by ligaments to form a framework for the rest of the body tissues. There are two parts to the skeleton:.
Bones are a site of attachment for ligaments and tendons, providing a skeletal framework that can produce movement through the coordinated use of levers, muscles, tendons and ligaments. The bones act as levers, while the muscles generate the forces responsible for moving the bones.
Bones provide protective boundaries for soft organs: the cranium around the brain, the vertebral column surrounding the spinal cord, the ribcage containing the heart and lungs, and the pelvis protecting the urogenital organs. Blood cells are formed from haemopoietic stem cells present in red bone marrow. Babies are born with only red bone marrow; over time this is replaced by yellow marrow due to a decrease in erythropoietin, the hormone responsible for stimulating the production of erythrocytes red blood cells in the bone marrow.
Yellow bone marrow Fig 1 acts as a potential energy reserve for the body; it consists largely of adipose cells, which store triglycerides a type of lipid that occurs naturally in the blood Tortora and Derrickson, It forms the framework for bones, which are hardened through the deposit of the calcium and other minerals around the fibres Robson and Syndercombe Court, Mineral salts are first deposited between the gaps in the collagen layers with once these spaces are filled, minerals accumulate around the collagen fibres, crystallising and causing the tissue to harden; this process is called ossification Tortora and Derrickson, The hardness of the bone depends on the type and quantity of the minerals available for the body to use; hydroxyapatite is one of the main minerals present in bones.
While bones need sufficient minerals to strengthen them, they also need to prevent being broken by maintaining sufficient flexibility to withstand the daily forces exerted on them. This flexibility and tensile strength of bone is derived from the collagen fibres. Over-mineralisation of the fibres or impaired collagen production can increase the brittleness of bones — as with the genetic disorder osteogenesis imperfecta — and increase bone fragility Ralston and McInnes, Also known as compact bone, this dense outer layer provides support and protection for the inner cancellous structure.
Cortical bone comprises three elements:. The periosteum is a tough, fibrous outer membrane. It is highly vascular and almost completely covers the bone, except for the surfaces that form joints; these are covered by hyaline cartilage. Tendons and ligaments attach to the outer layer of the periosteum, whereas the inner layer contains osteoblasts bone-forming cells and osteoclasts bone-resorbing cells responsible for bone remodelling. The periosteum has numerous sensory fibres, so bone injuries such as fractures or tumours can be extremely painful Drake et al, The intracortical bone is organised into structural units, referred to as osteons or Haversian systems Fig 2.
These are cylindrical structures, composed of concentric layers of bone called lamellae, whose structure contributes to the strength of the cortical bone.
Osteocytes mature bone cells sit in the small spaces between the concentric layers of lamellae, which are known as lacunae. Canaliculi are microscopic canals between the lacunae, in which the osteocytes are networked to each other by filamentous extensions.
In the centre of each osteon is a central Haversian canal through which the blood vessels, lymph vessels and nerves pass. Also known as spongy bone, cancellous bone is found in the outer cortical layer. It is formed of lamellae arranged in an irregular lattice structure of trabeculae, which gives a honeycomb appearance. The large gaps between the trabeculae help make the bones lighter, and so easier to mobilise. Trabeculae are characteristically oriented along the lines of stress to help resist forces and reduce the risk of fracture Tortora and Derrickson, The closer the trabecular structures are spaced, the greater the stability and structure of the bone Bartl and Bartl, Red or yellow bone marrow exists in these spaces Robson and Syndercombe Court, Red bone marrow in adults is found in the ribs, sternum, vertebrae and ends of long bones Tortora and Derrickson, ; it is haemopoietic tissue, which produces erythrocytes, leucocytes white blood cells and platelets.
Blood vessels in bone are necessary for nearly all skeletal functions, including the delivery of oxygen and nutrients, homoeostasis and repair Tomlinson and Silva, The blood supply in long bones is derived from the nutrient artery and the periosteal, epiphyseal and metaphyseal arteries Iyer, Each artery is also accompanied by nerve fibres, which branch into the marrow cavities.
Arteries are the main source of blood and nutrients for long bones, entering through the nutrient foramen, then dividing into ascending and descending branches. The ends of long bones are supplied by the metaphyseal and epiphyseal arteries, which arise from the arteries from the associated joint Bartl and Bartl, If the blood supply to bone is disrupted, it can result in the death of bone tissue osteonecrosis. A common example is following a fracture to the femoral neck, which disrupts the blood supply to the femoral head and causes the bone tissue to become necrotic.
The femoral head structure then collapses, causing pain and dysfunction. Bones begin to form in utero in the first eight weeks following fertilisation Moini, The embryonic skeleton is first formed of mesenchyme connective tissue structures; this primitive skeleton is referred to as the skeletal template.
These structures are then developed into bone, either through intramembranous ossification or endochondral ossification replacing cartilage with bone. Flat bones develop from membrane membrane models and sesamoid bones from tendon tendon models Waugh and Grant, The term intra-membranous ossification describes the direct conversion of mesenchyme structures to bone, in which the fibrous tissues become ossified as the mesenchymal stem cells differentiate into osteoblasts.
The osteoblasts then start to lay down bone matrix, which becomes ossified to form new bone. Long bones — typically longer than they are wide such as humerus, radius, tibia, femur , they comprise a diaphysis shaft and epiphyses at the distal and proximal ends, joining at the metaphysis. In growing bone, this is the site where growth occurs and is known as the epiphyseal growth plate. Most long bones are located in the appendicular skeleton and function as levers to produce movement.
Short bones — small and roughly cube-shaped, these contain mainly cancellous bone, with a thin outer layer of cortical bone such as the bones in the hands and tarsal bones in the feet. Flat bones — thin and usually slightly curved, typically containing a thin layer of cancellous bone surrounded by cortical bone examples include the skull, ribs and scapula.
Most are located in the axial skeleton and offer protection to underlying structures. Irregular bones — bones that do not fit in other categories because they have a range of different characteristics. They are formed of cancellous bone, with an outer layer of cortical bone for example, the vertebrae and the pelvis. Sesamoid bones — round or oval bones such as the patella , which develop in tendons. Long, short and irregular bones develop from an initial model of hyaline cartilage cartilage models.
Once the cartilage model has been formed, the osteoblasts gradually replace the cartilage with bone matrix through endochondral ossification Robson and Syndercombe Court, Mineralisation starts at the centre of the cartilage structure, which is known as the primary ossification centre.
Secondary ossification centres also form at the epiphyses epiphyseal growth plates Danning, Resting or quiescent zone — situated closest to the epiphysis, this is composed of small scattered chondrocytes with a low proliferation rate and anchors the growth plate to the epiphysis;. Growth or proliferation zone — this area has larger chondrocytes, arranged like stacks of coins, which divide and are responsible for the longitudinal growth of the bone;. Hypertrophic zone — this consists of large maturing chondrocytes, which migrate towards the metaphysis.
There is no new growth at this layer;. Calcification zone — this final zone of the growth plate is only a few cells thick. Bones are not fully developed at birth, and continue to form until skeletal maturity is reached. In rare cases, a genetic mutation can disrupt cartilage development, and therefore the development of bone. This can result in reduced growth and short stature and is known as achondroplasia.
The human growth hormone somatotropin is the main stimulus for growth at the epiphyseal growth plates. During puberty, levels of sex hormones oestrogen and testosterone increase, which stops cell division within the growth plate. As the chondrocytes in the proliferation zone stop dividing, the growth plate thins and eventually calcifies, and longitudinal bone growth stops Ralston and McInnes, Males are on average taller than females because male puberty tends to occur later, so male bones have more time to grow Waugh and Grant, Over-secretion of human growth hormone during childhood can produce gigantism, whereby the person is taller and heavier than usually expected, while over-secretion in adults results in a condition called acromegaly.
If there is a fracture in the epiphyseal growth plate while bones are still growing, this can subsequently inhibit bone growth, resulting in reduced bone formation and the bone being shorter. It may also cause misalignment of the joint surfaces and cause a predisposition to developing secondary arthritis later in life.
A discrepancy in leg length can lead to pelvic obliquity, with subsequent scoliosis caused by trying to compensate for the difference.
Bone remodelling has several functions, including mobilisation of calcium and other minerals from the skeletal tissue to maintain serum homoeostasis, replacing old tissue and repairing damaged bone, as well as helping the body adapt to different forces, loads and stress applied to the skeleton.
Calcium plays a significant role in the body and is required for muscle contraction, nerve conduction, cell division and blood coagulation. Serum calcium levels are tightly regulated by two hormones, which work antagonistically to maintain homoeostasis.
Calcitonin facilitates the deposition of calcium to bone, lowering the serum levels, whereas the parathyroid hormone stimulates the release of calcium from bone, raising the serum calcium levels. Osteoclasts are large multinucleated cells typically found at sites where there is active bone growth, repair or remodelling, such as around the periosteum, within the endosteum and in the removal of calluses formed during fracture healing Waugh and Grant, The osteoclast cell membrane has numerous folds that face the surface of the bone and osteoclasts break down bone tissue by secreting lysosomal enzymes and acids into the space between the ruffled membrane Robson and Syndercombe Court, These enzymes dissolve the minerals and some of the bone matrix.
The minerals are released from the bone matrix into the extracellular space and the rest of the matrix is phagocytosed and metabolised in the cytoplasm of the osteoclasts Bartl and Bartl, Once the area of bone has been resorbed, the osteoclasts move on, while the osteoblasts move in to rebuild the bone matrix. Osteoblasts synthesise collagen fibres and other organic components that make up the bone matrix. They also secrete alkaline phosphatase, which initiates calcification through the deposit of calcium and other minerals around the matrix Robson and Syndercombe Court, As the osteoblasts deposit new bone tissue around themselves, they become trapped in pockets of bone called lacunae.
Once this happens, the cells differentiate into osteocytes, which are mature bone cells that no longer secrete bone matrix. The remodelling process is achieved through the balanced activity of osteoclasts and osteoblasts. If bone is built without the appropriate balance of osteocytes, it results in abnormally thick bone or bony spurs.
Conversely, too much tissue loss or calcium depletion can lead to fragile bone that is more susceptible to fracture. Typical features on X-ray include focal patches of lysis or sclerosis, cortical thickening, disorganised trabeculae and trabecular thickening.
Anatomy And Physiology 1 Lecture Notes Pdf
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Anatomy and Physiology is a dynamic textbook for the two-semester human anatomy and physiology course for life science and allied health majors. The book is organized by body system and covers standard scope and sequence requirements. Its lucid text, strategically constructed art, career features, and links to external learning tools address the critical teaching and learning challenges in the course. The web-based version of Anatomy and Physiology also features links to surgical videos, histology, and interactive diagrams. The overall purpose of this preparatory course textbook is to help students familiarize with some terms and some basic concepts they will find later in the Human Anatomy and Physiology I course. The organization and functioning of the human organism generally is discussed in terms of different levels of increasing complexity, from the smallest building blocks to the entire body. This Anatomy and Physiology preparatory course covers the foundations on the chemical level, and a basic introduction to cellular level, organ level, and organ system levels.
Attribution CC BY. Overall, I found this text to be very comprehensive. There are some differences between the terminology and approaches compared to what I am used to, but there were no significant gaps that I could see. Comprehensiveness rating: 5 see less. A couple of things that might be different from other books are the way movements are described in skeletal muscle function, and the description of functional organization of the nervous system.
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It is an old science, having its beginnings in prehistoric times. Anatomy and physiology , which study the structure and function of organisms and their parts respectively, make a natural pair of related disciplines , and are often studied together. Human anatomy is one of the essential basic sciences that are applied in medicine.
Bones are an important part of the musculoskeletal system.
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PDF Usmle Step 1 Lecture Notes Anatomy Usmle Prep Uploaded By Jin Yong, usmle step 1 lecture notes by kaplan medical is most certainly the best book from the volume of 7 books for the preparation of medical license exam for the us this book is the most comprehensive and advanced one to date for achieving high. It will be most effective if you follow the sequence of videos. Students will be evaluated by lecture exams and laboratory. Pre-Requisite s None. Anatomy, Physiology and Biochemistry, Tanta. Day Lecture Reading Assessment 1. In this article, we are sharing with our audience the genuine PDF download of Dr.
Anatomy describes the structure and location of the different components of an organism to provide a framework for understanding. Human anatomy studies the way that every part of a human, from molecules to bones, interacts to form a functional whole. There are two major types of anatomy. Gross macroscopic anatomy is the study of anatomical structures that can be seen by the naked eye, such as the external and internal bodily organs. Microscopic anatomy is the study of tiny anatomical structures such as tissues and cells.
Human physiology is the study of the functions of the human body. These functions are complex and much more difficult to examine than most anatomical.
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