Biomedical Science Study Guide PDF

Biomedical Science Study Guide Term 1: September - December 2024 Dental hygiene Anatomical Terms and Concepts De9inition of anatomical position: The scienti9ic study of the physical structure of humans Anatomical position Standing erect Facing forward Arms at the side with palms facing forward Feet slightly apart (almost together) Directional term Meaning Medial Nearer to the midline Lateral Further from the midline or at the side Proximal Nearer to a point of attachment of a limb; nearer to centre of the body Distal Further from the point of attachment of a limb; situated away from centre of the body Anterior or ventral Nearer the front Posterior or dorsal Nearer the back Superior Nearer the head Inferior Further from the head Regional Terminology Body planes 3 planes lie at right angles to each other Divide body into sections- enables visualising or describing of body’s internal arrangement from various perspectives. Uses anatomical position as reference Median plane can also be referred to as sagittal plane Oral perspective Renal Diseases Renal Function Renal function is needed to: Maintain normal body 9luid volume and composition Essential for excretion of waste products and drugs Some previously fatal renal diseases can now be managed successfully The numbers of patients treated with kidney transplants is growing. Loss of Renal function - causes Renal Disease E.g. renal tract infections, glomerulonephritis, hypertension, diabetes, congenital abnormalities, Renal Hypofunction e.g. severe shock or haemorrhage Blockage of Renal out;low E.g. kidney stones, prostate tumours Chronic kidney Disease Chronic Kidney Disease (CKD) is characterized by irregularities in the structure and renal function for 3 months or more Potential impacts of chronic kidney disease Metabolic: Thirst, urination at night, electrolyte disturbance, glucose in urine Cardiovascular: Hypertension, Atheroma Gastrointestinal: loss of appetite, weight loss, nausea and vomiting, peptic ulver, hiccups Neuromuscular: headaches, drowsiness, tremors Haematological: Bleeding due to platelet dysfunction and/or anticoagulant medication, Anaemia due to de9iciency of erythropoietin Skin: bruising, rashes, prone to infection Immunological Signs & Symptoms of kidney disease Weight loss and poor appetite Shortness of breath (dyspnoea) Swollen ankles, feet or hands – due to water retention Increased need to urinate (especially at night) Insomnia Itchy skin Blood In urine (haematuria) General management of CKD Low protein diet Potassium restriction Salt or water control Dialysis/Transplant Prevention of further renal damage Dialysis can give normal life to up to 20% of patients but cannot prevent all complications Over 70% of patients on haemodialysis survive at least 5 years Renal transplant may then become necessary Renal Transplants This is now common, and survival of the graft can be up to 90% at one year Patients need to be immunosuppressed after the transplant Usual medications are: Ø Corticosteroid Ø Azathioprine Ø Cyclosporine Dental relevance – it is important to take note of renal disease as a patient may be experiencing dif9iculty or symptoms regarding: Candida Infections Herpes Simplex or Zoster Cytomegalovirus & Epstein- Barr Virus infections Lymphomas Skin, lip and cervical cancer Kaposi’s Sarcoma Cyclosporine may cause gingival overgrowth Bleeding tendencies Impaired drug excretion Hypertension Corticosteroid or other immunosuppressive treatment Underlying disease Infections with hepatitis B and other viruses Bone lesions of the jaw Diet – may be speci9ic diet, avoiding foods etc - Can take longer to heal - May be taking blood thinning medication Clinical dental relevance – CKD may express oral symptoms such as the following Dry mouth – increased risk of caries, exposed roots and risk of periodontal disease Halitosis – bad breath Metallic taste Salivary gland swelling Growth may be stunted – in children, may impact tooth eruption Tooth eruption delayed Enamel hypoplasia Hypertension – can cause gingival hypoplasia (en9lamed gums) can cause false pocketing and dif9iculty cleaning. Wider reading Chronic kidney disease (CKD) worsens over time. High blood pressure and diabetes are two common causes of CKD. There’s no cure for CKD Kidney diseases happen when your kidneys are damaged and can’t 9ilter your blood kidney disease can run in biological families Anyone can get chronic kidney disease. You’re more at risk for chronic kidney disease if you: Have diabetes. Have high blood pressure. Have heart disease. Have a family history of kidney disease. Have abnormal kidney structure or size. Are over 60 years old. Have a long history of taking NSAID (nonsteroidal anti-in9lammatory drugs) pain relievers. This includes over-the-counter (OTC) products and some prescription (https://my.clevelandclinic.org/health/diseases/15096-chronic-kidney-disease) Chronic Kidney Disease (CKD) is characterized by irregularities in the structure and renal function for 3 months or more (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6441594/) KEY ASPECTS TO UNDERSTAND: - Fucntions of kidney - Understanding what happens when fucntions fail - Dental impacts - Dental management – HOW PATIENT MANAGES AND HOW TO MANAGE IN CLINC Epithelium & Membranes - Epithelial Tissue – Epi (on or upon) Epithelial tissue covers the whole surface of the body - It is made up of cells closely packed and arranged in one or more layers - This tissue is specialised to form the covering or lining of all internal and external body surfaces - The epithelial tissue is one of the four main types of tissue structures of the human body, along with muscle tissue, nerve tissue, and connective tissue. - Tissues are cellular organizations with similar specializations. - Epithelia are formed of cells that line the cavities in the body and cover 9lat surfaces. - Of the four major tissue types found in the human body epithelial cells are by far the most proli9ic. How Do Epithelial Cells Differ from Other Cells? Avascular Capillaries do not reside within epithelial cell tissues Sensory Endings of neurons are present within epithelial cell tissues Perceive external stimulus (i.e. tactile) Gliding surface layer Epithelial cells slough off and glide in order to replace dead cells This function allows epithelial cells to maintain a closed barrier to the external environment Transitional Multi-layered epithelia are able to stretch Allows the urinary bladder to be distended or contracted without compromising it Tight barrier Desmosomes, hemi desmosomes, tight junctions Epithelium is held together more tightly than other cells Aids cells in withstanding mechanical stress Different from endothelial cells Endothelial cells line the insides of structures that aren’t exposed to the “outside” Ex. Blood vessels Functions of Epithelium Secretion & Lubrication - Secretion is the movement of material from one point to another. - such as a secreted chemical substance from a cell or gland. - In contrast, excretion is the removal of certain substances or waste products from a cell or organism Selective Absorption - The process of a liquid, gas or other substance being taken in. Protection - Cover the inner and outer linings of the bodies cavities and organs. Transcellular Transport - Movement of substances across the cell membrane – either in to or out of the cell Sensation - Nerve endings provide signals for sensory sensations such as taste, sight and smell. - In the nose, the sensory transducers are olfactory sensory neurons; in the ear, auditory hair cells; and in the eye, photoreceptors. Movement - Some epithelial cells have cilia which aid in moving substances. - These work by a sweeping motion. Characteristics of Epithelium The most cellular tissue in the body Forms semi- permeable membranes Avascular – without blood vessels nutrients diffuse in from underlying connective tissue Good nerve supply Cells are tightly packed together Rapid cell division Characteristics Cellularity Polarity Supported by connective tissue Avascular Regenerative Basement Membrane Types & Categories of Epithelium Ø Simple – single layer of cells, all cells in contact with basement lamina Ø Stratified – multiple layers of cells, not all cells in contact with basement lamina Ø Transitional Ø Pseudostratified – looking histologically, it may appear that not all cells are in contact with basement lamina due to varying nuclei height Ø Squamous (shape) – this and flat Ø Cuboidal (shape) – cube shaped Ø Columnar (shape) – rectangular in shape Types and Categories of Epithelium Classi9ication of Epithelium Simple Epithelium Simple Squamous Epithelium - These consist of a single layer of 9lattened cells. - The thinness of these cells facilitates the transfer of materials across the epithelium. - Found kidney, alveoli of lungs, circulatory system Simple Cuboidal Epithelium - These consist of a single layer of cuboidal cells - This epithelium is often associated with absorption, secretion or excretion of waste material. - Found kidney, Simple Cuboidal Epithelium Simple Columnar Epithelium - These consist of a single layer of cells that are taller than they are wide - This epithelium is often associated with absorption or secretion. - Found ears, eye, nose, oral cavity Pseudostrati9ied (Pseudo – fake/false) Columnar Epithelium - These appear to be strati9ied because of the nuclei of the epithelial cells are at different levels - All cells are in contact with the basement membrane, but not all cells reach the lumen - Inner ear, prostate gland Strati;ied Epithelium Strati9ied Squamous Epithelium - These have multiple layers of cells - They become 9lattened as they move from the basal layer to the apical layer - They provide protection from abrasion Can be Keratinised or non- Keratinised - Non- keratinised – no outer layer of dead cells, eg within oral cavity - Keratinised- outer surface composed of dead cells giving greater protection (skin) Strati9ied Cuboidal Epithelium - These have multiple layers of cells - The outermost layer being cuboidal - Limited distribution - Found in utera, anus uterus Strati9ied Columnar Epithelium - Multiple layers - Primary function is protection - Topmost layer is made up of columnar epithelial cells Transitional Epithelium - These have multiple layers of cells - The outermost layer has much larger cells, which are pear/dome shaped - These cells change shape during contraction - Allows for stretching - Featured mainly in urinary tract - Allows bladder to stretch Membranes Membranes - Membranes are sheets of tissue composed of cells They cover or line internal structures or cavities The main membranes are: - Mucous - Serous - Synovial - Cutaneous Mucous Membrane - This is an epithelial membrane containing mucous cells - It lines the body cavities that are open to the external environment - It has a protective function - It is rich with mucous glands that secrete a gel like 9luid to help keep the membranes moist - Mucous is produced from the epithelial exocrine glands The 9luid consists of: 95% water 05-5% mucins 1% inorganic salts 05-1% proteins Trace - lipids and mucopolysaccharides Serous Membrane - Lines the body cavities that are not open to the external environment - It is an epithelial membrane composed of mesodermal derived epithelium - Composed of two layers: Parietal – outer layer Visceral – inner layer - Serous 9luid lubricates The serous membranes are located in four locations and are named based on these locations. The pleura surrounds the lungs and thoracic cavity, the pericardium surrounds the heart, the tunica vaginalis surrounds the testes in males, and the peritoneum surrounds the abdominal cavity and abdominal organs. “A thin lining of closed cavities of the body, consisting of a single layer of squamous epithelial cells (MESOTHELIUM) resting on a thin layer of CONNECTIVE TISSUE, and covered with secreted clear 9luid from blood and lymph vessels” Synovial Membrane - This lines the cavity of a freely moveable joint - Fibroblasts release hyaluronan into the joint cavity - Hyaluronan traps available water to form the synovial 9luid - Nourishes cartilage - Eg. Knee and hip joints Cutaneous Membrane - It is a strati9ied squamous epithelial membrane - Rests on top of connective tissue - Covered with dead keratinized cells that protect the body from pathogens - Also known as skin Cartilage Cartilage, what is it and why do we need to know about it? A 9irm, avascular, non-calci9ied connective tissue. Forms much of the temporary skeleton in the embryo / foetus. (substructure for endochondral ossi9ication) Frequently serves as a model or template for the bones of the skeleton. It is also present on articular surfaces of free moving joints allowing for 9lexibility Cartilage is avascular and alyphatic “There are three types of cartilage in your body. Cartilage does everything from helping your joints move smoothly to absorbing impacts. Your nose and ears are made of cartilage. Cartilage damage is one of the most common results of sports injuries and other traumas. How long it takes to recover depends on where the injury is and how severely your cartilage is torn” Absorbing shock: Cartilage cushions your bones and joints when you move and use them. It absorbs force and reduces how much stress an impact puts on your bones. Think about the difference between jumping up and down in bare feet and wearing running shoes. Cartilage acts like the cushion in your sneakers on the inside of your joints and around your bones. Reducing friction: Cartilage lubricates your joints. It helps your bones slide past each other without rubbing together. This lets your joints work as smoothly as they should and reduces wear and tear on them. Supporting structures in your body: Cartilage helps your joints keep their shape while moving. It also connects other tissue together and to your bones. Muscles, tendons and ligaments are connected to cartilage throughout your body. From the 7th week of embryonic life, ossi9ication or ossogenisis, replaces cartilage with bone continuing into early childhood. Cartilage grows in 2 ways – Interstitial growth Chondrocytes divide and create more matrix inside the cartilage, causing it to grow in length. This process mainly occurs during childhood and adolescence. Appositional growth New chondroblasts from the perichondrium add new surface layers of matrix to the existing matrix, causing the cartilage to expand 65% of cartilage is water, decreases with age – the rest is matrix TMJ The most important cartilage in the head and neck is the TMJ. Issues with this joint may have a signi9icant impact. It may mean the patient could present with limited opening & discomfort Cartilage depends on its surrounding connective tissue for its cellular nutrition, it is called the perichondrium which is often described as a 9ibrous connective tissue sheath Structure of Cartilage Cartilage is made up of cells and a matrix The matrix is 9ibres / collagen/ intra cellular substances The cells are immature chondroblasts -these produce cartilage matrix chondrocytes which are in essence mature chondroblasts that maintain the cartilage matrix Matrix: Ground substance Highly hydrogenated gel composed of proteoglycan, chondronectin & water Fibres: Type and number of 9ibre depends on the type of cartilage 40% of dry weight of cartilage, giving it strength Perichondrium: Capsular sheath that surrounds cartilage Three types of cartilage: Hyaline Fibrous Elastic All cartilage starts as Hyaline but then modi9ies according to need. Hyaline cartilage Principal type of cartilage, particularly in foetus and infants Small groups of chondrocyte cells Matrix is smooth and solid Appears as a smooth bluish white, glassy tissue Not easily repaired following injury Location: Articulating surfaces of bone Costal cartilages which attach the ribs to the sternum Cartilages of larynx, trachea and bronchi Fibrous cartilage Dense, tough and slightly 9lexible tissue Groups of chondrocytes separated from each other by thick bundles of collagen 9ibres Collagen 9ibres arranged predominantly in tight parallel bundles Strongest and least 9lexible Location: Intervertebral discs Knee and jaw joints Surrounding the rim of the bony sockets of the hip and shoulder joints Pubic symphysis Elastic cartilage Elastic 9ibres feature in the intracellular matrix The least common type of cartilage tissue - The matrix of elastic cartilage is dominated by large elastic 9ibres Elastic cartilage Location: Pinna of the ear Epiglottis Forming part of the tunica media of blood vessel walls Bone Function of bone: Besides serving as a framework for soft tissue, bones permit locomotion, protect vital organs, facilitate breathing, play a role in electrolyte homeostasis, and house hematopoietic sites. Bone remodelling continues throughout life, driven by physiologic demands. Human infants typically have 270 bones, fusing into around 206 in the human adult. - Bone consists largely of collagen forming a soft framework, calcium phosphate hardens this framework giving it strength - Bones contain 99% of the body's calcium Long bones Consist of a long shaft or diaphysis and two articular surfaces, with central bone marrow cavity E.g. limb bones such as tibia or femur Diaphysis: Also known as the shaft. The diaphysis contains the bone medulla, which houses yellow marrow. Epiphysis: Located at the tip of the long bone, typically responsible for articulation. The epiphysis is also the primary source of red marrow in long bones, the site of erythropoiesis. Metaphysis: The region between the diaphysis and epiphysis that contains the epiphyseal plate in children. Epiphyseal plates are responsible for linear bone growth and remain cartilaginous until after puberty. After ossi9ication, the metaphysis becomes primarily responsible for transferring mechanical loads from the epiphysis to the diaphysis Short bones Cube shaped bones E.g. wrist and ankle bones Short bones also evolve by endochondral ossi9ication but are smaller and take on different shapes. Flat bones Thin and often curved E.g. skull bones such as occipital bone or parietal bone Irregular bones Irregular bones Irregular and complicated shapes E.g. bones of spine Sesamoid bones Embedded in tendons E.g. the patella What’s the difference between the axial and appendicular skeleton? Your axial skeleton is made up of the bones in your head, neck, back and chest. Your appendicular skeleton is made up of everything else — the bones that attach (append) to your axial skeleton. Your appendicular skeleton includes the bones in your shoulders, pelvis and limbs, including your arms, hands, legs and feet. Your axial skeleton provides support and cushioning for your brain, spinal cord and organs in your body. Muscles in your body that move your head, neck and trunk attach to your axial skeleton. These muscles help you breathe and steady parts of your appendicular skeleton. Development of bone Bone ossi9ication, or osteogenesis, is the process of bone formation. This process begins between the sixth and seventh weeks of embryonic development and continues until about age twenty-9ive, although this varies slightly based on the individual. Muscle Deﬁnition noun; A band of ﬁbrous tissue in a human or animal body that has the ability to contract, producing movement in or maintaining the position of parts of the body. Myoﬁbril A muscle tissue is made up of muscle cells, which in turn consist of several myoﬁbrils The myoﬁbril is the contractile thread of a muscle These extend from one end of the muscle ﬁbre to the other. Myoﬁbrils are bundles of protein ﬁlaments that contain the contractile elements of the cardiomyocyte, that is, the machinery or motor that drives contraction and relaxation Myoﬁbrils are cylindrical microﬁlamentous organelles with a diameter of approximately 1 µm Myoﬁbrils account for approximately 80% of the volume of a muscle ﬁbre The smallest fundamental contractile unit of the myoﬁbril is called the sarcomere Sarcomere A sarcomere is the basic contractile unit of muscle ﬁbre. Each sarcomere is composed of two main protein ﬁlaments—actin and myosin— which are the active structures responsible for muscular contraction. The sarcomere is composed of long ﬁbrous proteins that slide past each other resulting in the appearance of dark and light bands under the microscope The sarcomere is regarded as the basic structural unit of a muscle. Muscle Fuel Muscle cells fuel their actions by converting chemical energy in the form of Adenosine Triphosphate (ATP) ATP, in fact, is the only molecule able to provide energy to muscle ﬁbers to power muscle contractions This is derived by the metabolism of food into chemical energy Through metabolic processes, ATP becomes hydrolysed into ADP, or further to AMP, and free inorganic phosphate groups. Functions of Muscle Posture/Muscle Tone Stability Mobility/Movement Circulation Respiration Digestion Temperature Regulation/Heat Production Organ Protection Urination Muscle tone This is a state of sustained partial contraction of a muscle Muscle Fatigue Not enough oxygen and nutrients Build-up of waste products Properties of Muscle Tissue Muscle cells share several properties Ø Contractility Ø Excitability Ø Extensibility Ø Elasticity Contractility - The ability of muscle to forcefully shorten - For a muscle to work, one will need to ﬂex and the other contract - Muscles can only pull, never push - Prime movers contract and antagonists relax Excitability The ability to respond to a stimulus Delivered from a motor neurone or hormone Extensibility The ability for a muscle to be stretched Can be stretched up to 3x contracted length without injury Temperature: Muscles can produce heat through a process called ATP hydrolysis, which occurs when ATP is broken down into ADP and inorganic phosphate Heat production This process releases energy and heat, which is especially noticeable during exercise or shivering. Temperature regulation When the body is too cold, the hypothalamus in the brain triggers skeletal muscles to contract to generate heat and raise body temperature. This is a negative feedback loop that helps maintain temperature homeostasis. Levers Levers in our body are formed from bones, joints and muscles. A lever consists of: a rigid structure (bone) a force acting upon it (muscle) to produce a turning movement (angular motion) Types of muscle Striated/Skeletal Muscle - About 40% of body weight - Some elasticity via tendons that contain collagen and elastin - Blood vessels and nerves associated with each striated muscle, transport blood and nutrients removing CO2 Contracts to move limbs Maintains posture Both ends of muscle articulate the skeleton Attached to the bones by tendons Has blood vessels and nerves associated with it Under voluntary control Each skeletal muscle ﬁbre is roughly cylindrical in shape Fibre arrangement depends on the function of the muscle Each muscle ﬁbre has a long cylindrical shape measuring between 0.02 to 0.08 mm in diameter They vary in length between 40mm to 35cm - Fibers have an outer membrane called the sarcolemma which contain large numbers of myoﬁbers with many nucelli lying underneath - known as striated muscles, because the ﬁlaments of actin and myosin that power their contraction are organized into repeating arrays, called sarcomeres, that have a striated microscopic appearance. - Healthy skeletal muscle harbours a robust regenerative response that becomes inadequate after large muscle loss or in degenerative pathologies and aging - Striated muscles are required for whole-body oxygen supply, metabolic balance, and locomotion Smooth Muscle - smooth muscle can be described as an involuntary, non-striated muscle. - Smooth muscle consists of thick and thin ﬁlaments that are not arranged into sarcomeres giving it a non-striated pattern. On microscopic examination, it will appear homogenous - Smooth muscle cytoplasm contains a large amount of actin and myosin. Actin and myosin act as the main proteins involved in muscle contraction - Actin ﬁlaments attach to dense bodies that are spread throughout the cell - Another important structure is the calcium- containing sarcoplasmic reticulum which aids in sustaining contraction - The shape of the smooth muscle is described as fusiform, which is described as being round in the centre and tapering at each end - Smooth muscle can tense and relax but has greater elastic properties than striated muscle. This is important in organ systems like the urinary bladder where contractile tone must be preserved. Found where movement of soft tissues structures is required e.g. Walls of blood and lymphatic vessels Alimentary canal Cells are spindle shaped Under the autonomic nervous system Only relaxes for short periods of time Contraction of smooth muscle can be sustained for long periods if required The cells are long and narrow, and spindle shaped with one centrally place nucleus They are 0.005mm to 0.01mm in diameter and 0.03mm to 0.2mm long Cardiac Muscle - Cardiac muscle (or myocardium) makes up the thick middle layer of the heart - The myocardium is surrounded by a thin outer layer called the epicardium (AKA visceral pericardium) and an inner endocardium. The heart is made up of three layers—pericardium, myocardium, and endocardium. - The endocardium is not cardiac muscle and is comprised of simple squamous epithelial cells and forms the inner lining of the heart chambers and valves - The pericardium is a ﬁbrous sac surrounding the heart, consisting of the epicardium, pericardial space, parietal pericardium, and ﬁbrous pericardium - The cardiac muscle is responsible for the contractility of the heart and, therefore, the pumping action Cellular level - Cardiac muscle cells (cardiomyocytes) are striated, branched, contain many mitochondria, and are under involuntary control - Cardiac muscle cells contain branched ﬁbres connected via intercalated discs that contain gap junctions and desmosomes. These interconnections allow the cardiomyocytes to contract together synchronously to enable the heart to work as a pump. - The functional unit of cardiomyocyte contraction is the sarcomere, which consists of thick (myosin) and thin (actin) ﬁlaments, the interactions between which form the basis of the sliding ﬁlament theory - Only found in the wall of the heart - Exhibits rhythmic contractions - Under the autonomic nervous system - Each ﬁbre is roughly rectangular in shape - Has an intrinsic pacemaker system - Has intercalated discs Intercalated discs (ICDs) are structures in the heart that connect cardiac muscle cells together. Muscles of Mastication Connective Tissue It protects, supports, binds, transports and plays a role in immunity Protects and supports – bones and the pericardium are connective tissue that protect and support. Eg. Kidneys are anchored by connective tissue Transport – blood transport oxygen, CO2, ions, electrolytes, waste etc Immunity – lymphatic ﬂuids and white blood cells All connective tissues are made up of cells, gels and ﬁbers - Cells: blasts and cytes. Immature cells of connective tissue include ﬁbroblasts, chondroblasts, hemocytoblasts Mature cells such as adipocytes (fat cells), osteocytes (bone cells), chondrocytes (cartilage cells), erythrocytes (red blood cells), leucocytes (white blood cells) - Cells create the gels or ground substance, this is the bulk of connective tissue This is made of glycosaminoglycans (GAGS), proteoglycans, glycoproteins - Fibers: collagen ﬁbres, elastic and reticular Collagen ﬁbres strong and rigid, adds strength Elastic add ﬂexibility Reticular provide a network within connective tissue often in lymphatic tissue, net like structure works for ﬁltration EVERY CONNECTIVE TISSUE CONTAINS CELLS, GELS AND FIBERS. THE TYPE OF CONNECTIVE TISSUE IT IS DEPENDS OF THE COMBINATION OF THESE ELEMENTS. Connective tissue proper - Binds holds etc - DENSE Regular – ﬁbres in a regular pattern, tendons and ligaments, bone to bone, muscle to bone direct resistance Irregular – ﬁbers are arranged irregularly, need to resist pulling in all direction, dermis for example, connective tissue under skin elastic – arteries, need to be able to stretch to handle power of blood pumping - LOOSE Areolar – binds and anchors internal organs Reticular – lymphatic organs Adipose – fat tissue Supportive connective tissue - Supports weight of the body Bone Cartilage Hyaline, elastic, ﬁbrocartilage Fluid connective tissue - Blood https://youtu.be/0z9rF2kJaXs?si=7e7-mdRnEucw8k6j LECTURE: What is connective tissue? A group of tissues that maintain the form of the body and its organs and provide cohesion and internal support. Several types of tissues that vary in their: Density Cellularity Being specialised - Fibroblasts, adipocytes, macrophages, mast cells, plasma cells, eosinophils In a matrix made up of glycoproteins, ﬁbrous proteins and glycosaminoglycans Extracellular matrix The extracellular matrix is the main feature in tissues with a mechanical function (ligaments, tendon & bone) Cells are the main feature in tissues specialised for protection (haemopoietic tissue, blood - white blood cells) or metabolic maintenance (adipocytes, blood - red blood cells). Also known as ground substance Amorphous gelatinous material Transparent, colourless Fills the spaces between cells and ﬁbres, also enable transportation of metabolites Consists of large protein molecule: glycosoaminoglycans (GAGs) – link together making larger molecules: proteoglycans which absorb water Good at resisting compressive forces Connective Tissue Cells Fixed cells: - Fibroblasts - Adipocytes - Macrophages - Mast cells Transient Cells: - Plasma cells - Eosinophils Fibres of the Connective Tissue Secreted by ﬁbroblasts Form a supporting network to which cells attach Three types: - Elastic - Collagen - Reticular - Loose connective tissue - Dense connective tissue Temporomandibular joint TMJ is a synovial, condylar and hinge-type joint. The joint involves ﬁbrocartilaginous surfaces and an articular disc which divides the joint into two cavities. These superior and inferior articular cavities are lined by separate superior and inferior synovial membranes Capsule - The capsule is a ﬁbrous membrane that surrounds the joint and attaches to the articular eminence, the articular disc and the neck of the mandibular condyle. Articular disc - The articular disc is a ﬁbrous extension of the capsule that runs between the two articular surfaces of the temporomandibular joint. The disc articulates with the mandibular fossa of the temporal bone above and the condyle of the mandible below. The disc divides the joint into two sections, each with its own synovial membrane. The disc is also attached to the condyle medially and laterally by the collateral ligaments. The anterior disc attaches to the joint capsule and the superior head of the lateral pterygoid. The posterior portion attaches to the mandibular fossa and is referred to as the retrodiscal tissue. Retrodiscal tissue - Unlike the disc itself, the retrodiscal tissue is vascular and highly innervated. As a result, the retrodiscal tissue is often a major contributor to the pain of Temporomandibular Disorder (TMD), particularly when there is inﬂammation or compression within the joint Bone 2 types: - Compact bone consists of closely packed osteons or haversian systems. The osteon consists of a central canal called the osteonic (haversian) canal, which is surrounded by concentric rings (lamellae) of matrix. Between the rings of matrix, the bone cells (osteocytes) are located in spaces called lacunae. Small channels (canaliculi) radiate from the lacunae to the osteonic (haversian) canal to provide passageways through the hard matrix. In compact bone, the haversian systems are packed tightly together to form what appears to be a solid mass. The osteonic canals contain blood vessels that are parallel to the long axis of the bone. These blood vessels interconnect, by way of perforating canals, with vessels on the surface of the bone. - Spongy bone , light, porous bone enclosing numerous large spaces that give a honeycombed or spongy appearance. The bone matrix, or framework, is organized into a three-dimensional latticework of bony processes, called trabeculae, arranged along lines of stress. The spaces between are often ﬁlled with marrow and blood vessels. Blood - Blood is considered a specialized connective tissue as it connects all systems of the body and transports oxygen, nutrients, and wastes Intro to microbiology The study of organisms too small to be seen clearly with the naked eye (0.1-0.2mm diameter) Known as micro-organisms or microbes Includes: 1. Bacteria 2. Viruses 3. Fungi 4. Algae 5. Protozoa Eukaryotes Large & complex Has clearly deﬁned nucleus Membrane bound organelles Single or multi-cellular - eukaryote, any cell or organism that possesses a clearly deﬁned nucleus. - The eukaryotic cell has a nuclear membrane that surrounds the nucleus, in which the well- deﬁned chromosomes are located Prokaryotes Small & simple Have a nucleoid with no membrane Lacks internal membrane structure Always unicellular - Prokaryotes are organisms whose cells lack a nucleus and other organelles Nucleus Eukaryotic cells have a nucleus that surrounds the cell's DNA, while prokaryotic cells lack a nucleus and instead have DNA in a central region called the nucleoid. Organelles Eukaryotic cells have a plasma membrane and other membrane-bound organelles, while prokaryotic cells lack these organelles. Chromosomes Eukaryotic cells have multiple linear chromosomes, while prokaryotic cells typically have a single circular chromosome. Cell wall Prokaryotic cell walls may be made of peptidoglycan or pseudopeptidoglycan, while eukaryotic cells have a cell wall as their outermost layer. Reproduction Eukaryotes reproduce sexually, while prokaryotes reproduce asexually. Ribosomes In prokaryotes, ribosomes are about 40% protein and 60% rRNA, while in eukaryotes, ribosomes are about half protein and half rRNA. Attachments Prokaryotes have hair-like appendages called pili that help them attach to various environments. Endotoxins VS Exotoxins Microbes are found almost everywhere around us, both inside and outside the living organisms. These pathogens produce toxins which are the major causes of the infections. These toxins are categorized into two types: Endotoxins Exotoxins The basic diqerence between endotoxins and exotoxins lies in how these toxins are produced by bacteria The endotoxins and exotoxins widely vary in toxicity and lethality. Exotoxins are more potent and often fatal when compared to endotoxins. Enzymes Enzymes are proteins that speed up chemical reactions in living organisms without being consumed or permanently altered by the reaction Digestion: Enzymes break down large nutrient molecules, such as proteins, carbohydrates, and fats, into smaller molecules. For example, amylase breaks down starch into sugars, and lipase breaks down fats and oils into glycerol and fatty acids. Metabolism: Enzymes regulate the rate of chemical reactions that occur in all aspects of cell metabolism. Energy conservation: Enzymes help conserve and transform chemical energy. Macromolecule construction: Enzymes help construct cellular macromolecules from smaller precursors Commensals Commensals are those type of microbes that reside on either surface of the body or at mucosa without harming human health. The microbes living in harmony with human mostly consist of bacteria, also known as commensal bacteria, which are 10 times more than the cells present in our body. These bacteria are present at a particular location of the body such as the skin surface, oral cavity, intestine, nasopharyngeal cavity, mucosal surface of the genital tract, and other anatomical places that provide a suitable environment for proper growth and multiplication

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