Introduction to Tissues PDF

Introduction to tissues Tissue : structural and functional related cells and their external environment that together perform common function Histology: study of the normal structure of tissue (all tissues share 2 basic components) - Discrete population of cells related in structure and function...

Introduction to tissues Tissue : structural and functional related cells and their external environment that together perform common function Histology: study of the normal structure of tissue (all tissues share 2 basic components) - Discrete population of cells related in structure and function - Surrounding material called Extracellular Matrix which differ in composition in each tissue type Epithelial tissue Connective tissues Muscle tissues Nervous tissues - Sheets of tightly packed cells - Connect all other tissues together - Contract and generate force - Generate, send and receive message - Little ECM - Cells are scattered through the ECM - Little ECM - Include cells that support the neurons with - Covers and lines body surfaces and cavities - Bind, support protect and allow some ECM and form parts of glands transportation of substances EXTRACELLULAR MATRIX: composed of substances surrounding the cells in a tissue that function to - Provide the tissues with strength to resist tensile (stretch) and compressive forces - Direct cells to their proper places within a tissues & hold cells in their proper positions - Regulate the development, mitotic activity, and survival of cells GROUND SUBSTANCE PROTEIN FIBERS gel-like substances that contain extracellular fluid with water, ion, entwined fibrous protein subunits that provide tensile strength nutrients, and other solutes and 3 families of macromolecules Glycosaminoglycans Proteoglycans Glycoprotein Collagen fibers Elastic fibers Reticular fibers: carbohydrate large molecules with protein with 20 different types of made of protein type of collagen fiber polymers that attract GAG chains attached carbohydrate chains collagen fibers are surrounded by BUT thinner/shorter water and form a gel- to a core protein, that play roles in cell made in the body; glycoproteins; may than regular collagen; like substances in the contributing to tissues adhesion, matrix make up 20-25% of all stretch to 1/2 time interweaves to form a ECM providing structure, cell formation and protein in the body; their resting length scaffold that support hydration and signaling, and ECM signaling resemble entwined without breaking the cells and ground cushioning organization. Acts as a (Fibronectin) pieces of a steel cable; (distensibility) and substance of tissues; (Hyaluronic Acid) barrier to diffusion of very resistant to then return to their form "webs" in some substances though the tension and pressure original length organs to trap foreign ECM (Aggrecan) (elasticity) cells Cells junction: Connections of neighboring cells Tight (occluding) junctions: Desmosomes: Gap junctions in a tissue linked to one another by integral junctions composed of integral locking proteins in junction composed of integral linker proteins in small pores made of protein channels in adjacent protein adjacent plasma membrane; prevent passage of adjacent plasma membranes; distribute mechanical plasma membranes; allow small substances to pass macromolecules, although some are leaky and don’t stress freely provide a complete seal Epithelial tissue: found in on every external and internal body surface, so acts as a barrier between the body and the environment Protection Immune defense Secretion Transport into other tissues Sensation shield underlying tissues from Cells of the immune system are form glands that produces substances selectively permeable barriers that most epithelia supplied with nerves that mechanical and thermal injury; produce scattered through epithelial tissues such as sweat, oil and hormones allow certain substances to pass by detect changes in internal and external hard protein keratin; undergoes mitosis passive or active transport environment; specialized epithelial cells rapidly and frequently are responsible for some sensation Component of epithelial Basement membrane: anchors the epithelial tissues to the underlying connective tissue and made of: (1) Basal lamina Shape of the cells - this is the ECM of the epithelial tissues; consist of collagen fibers and ground substance Squamous cells Cuboidal cells Columnar cells (2) Reticular lamina flattened cells short cells tall and - produce by connective tissue beneath epithelial tissue; made of reticular fibers & ground substance elongated Epithelial cells have 1 side in contact with the extracellular space (apical Surface), & 1 contact with deeper cells/basal cells lamina (basal Surface) Classification of epithelia Number of cells Simple epithelia Pseudostratified epithelia Stratified epithelia One cell layer thick, Does not work for protection; Lines hollow organs and surfaces where diffusion or transport occurs; single layer of cells that appears to be multilayered more than one layer of cells Classification of epithelia by number of cells and shape of the cells Simple Squamous Epithelia Simple Cuboidal Epithelia Simple Columnar Epithelia Pseudostratified Columnar Epithelia (simple) Single layer of flat cells; Resemble fried eggs that Single layer of roughly cube-shaped cells; Appear Single layer of tall cells; Appear rectangular in a Single layer of cells that appears to be stratified; fit together like floor tiles; Diffusion occurs square with a large, central nucleus; Diffusion section; Some have folds of the apical surface Looks this way because nuclei are at different quickly across cells; Found in air sacs of lungs, occurs and some secrete substances; Found in (microvilli); Some have cilia, which move something heights and some cells are shorter; Most are serous membranes, and lining of blood vessels kidney tubules and glands along the apical surface; Some produce secretions; ciliated; Include goblet cells that secrete mucus; Found in small intestine, uterine tube, kidney Found in respiratory passages and nasal cavities tubules and glands for protection Stratified Squamous Epithelia Stratified Cuboidal Epithelia Stratified Columnar Epithelia Transitional Epithelia Nonkeratinized stratified squamous epithelia has Rare in the human body; Two layers of cuboidal Rare in the human body; Few layers of cells that Cells in the basal layer are cuboidal and apical distinct nucleated cells on the apical surface; cells; Lines the ducts of sweat glands are columnar in apical layers and cuboidal in basal cells are dome-shaped when the tissue is relaxed; Found in epithelium of mouth, pharynx, layers; Found in ducts of salivary glands; parts of When stretched, apical cells appear squamous; esophagus, anus, and vagina male urethra, and the conjunctiva (membrane Found in lining of kidneys, ureters, urinary lining the surface of the eye) bladder, and urethra Connective tissue functions Connecting and binding Support Protection Transport Bind tissue layers together in organs and anchor Certain connective tissues, such as bone and Bone protects internal organs; Cartilage and fat Blood, which is the main transport medium in the organs in place and to one another cartilage, support the weight of the body tissue provide shock absorption; Elements of the body, is a type of connective tissue immune system are found within connective tissues Classification of connective tissue (1) General connective tissue (Connective Tissue Proper) (2) Specialized connective tissue - Widely distributed in the body, where it connects tissues and organs to one another and forms part of the internal architecture. (loose, dense, reticular, adipose tissues) - Cartilage, bone, blood, etc. Cell that FORM connective tissues Fibroblasts Adipocytes - produce protein fibers, ground substance and other ECM - fat cells with single large inclusion that contains lipids with elements; usually lie close to collagen fibers that they produce organelles pushed to the perimeter Cells OF connective tissue Mast cells Phagocytes Other immune cells - Cells of the immune system with cytosolic - Immune cells that phagocytize foreign substances, - Other cells of the immune inclusions (or granules) containing inflammatory microorganisms, and dead and damaged cells; system can move in and mediators such as histamine Includes macrophages and neutrophils out of connective tissues depending on the needs of the body Type of connective tissue proper Loose (Areolar) Connective Tissue Dense Irregular Connective Tissue Dense Regular Collagenous Connective Tissue Ground substance with all 3 types of protein fibers, fibroblasts, and Composed of protein fibers with mostly collagen fibers that are Contains thick collagen fibers arranged in parallel bundles; Resist other cells including immune cells; Jelly-like consistency; Found arranged haphazardly; Strong tissue that resists tension in all 3 tension in one direction; Found in tendons (which join muscle to deep to the epithelium of the skin and in membranes; Supports and planes; Found in dermis and around organs and joints bone) and ligaments (which join bone to bone) houses blood vessels Dense Regular Elastic Connective Tissue Reticular Tissue Adipose Tissue Also known as “elastic tissue;” Consists of mostly parallel elastic Includes numerous reticular fibers(typically collagenous fibers) Fat tissue consisting of adipocytes and surrounding fibroblasts and fibers with randomly oriented collagen fibers; Allow organs to produced by surrounding fibroblasts; Form fine, mesh like networks ECM; Adipocytes can increase in size; Functions in insulation, warmth, shock absorption, protection, and energy reserve stretch; Found in the lining of the large blood vessels and some for support and weblike nets that trap foreign cells; Forms part of ligaments basement membrane Special connective tissue Cartilage Bone Blood - Tough, flexible tissue that absorbs shock and is - Supports the body, protects vital organs, provides attachment - E C M is fluid and is called Plasma, with water, dissolved solutes, resistant to tension, compression, and shearing forces sites for muscles, stores calcium salts, and houses bone marrow, and globular proteins which produces our red blood cells and stores fat - ECM is solid and gel-like with glycosaminoglycans, - Cells are erythrocytes (red blood cells), which carry oxygen, Bone Cells proteoglycans, collagen fibers, and elastic fibers Osteoblasts Osteocytes Osteoclasts leukocytes (white blood cells), which function in immunity, and cell Carry out bone Mature osteoblasts Multinucleated fragments called platelets which function in blood clotting Chondroblast Chondrocytes deposition surrounded by ECM; cells that carry out Immature cartilage cells Mature cartilage cells, Produce substances bone resorption which live in small cavities for bone maintenance (break down) called lacunae Bone Remodeling Bone deposition and bone resorption are constantly occurring in Surrounded by an outer sheath of dense irregular connective tissue healthy bone called the perichondrium, which supplies blood to the cartilage Muscle cells (myocytes): excitable cells that respond to electrical/chemical stimulation; cytoplasm is filled with bundle of proteins called myofilaments; surrounded by small amount of ECM (endomysium) Striated muscle cells Smooth Muscle Cells Myofilaments: organized into regions that produce dark & light areas called “bands;” Alternating light-dark bands are Striations Myofilaments: irregular bundles scattered in cytoplasm, no striations are visible Type of muscle tissues Skeletal Muscle Cardiac Muscle Smooth Muscle - Found attached to the skeleton to produce body movement; Found only in the heart; Involuntary contractions; Shorter Found in the walls of hollow organs, walls of blood vessels, the eyes, the Controlled by the nervous system; Typically, voluntary movements; than skeletal muscle cells with branches and a single nucleus; skin, and the ducts of some glands; Involuntary contractions; Cells are Formed by the fusion of Intercalated discs, flattened, with a single nucleus; embryonic myoblasts resulting in which contain gap Gap junctions in the plasma large, multinucleate cells (also junctions and tight membrane connect cells to called Muscle Fibers) junctions, are found other smooth muscle cells between cells and permit heart muscle to contract as a unit Nervous Tissue Makes up majority of the brain, spinal cord, and nerves; ECM is different from other tissues and contains few protein fibers, mostly ground substance with unique proteoglycan Cells include Neurons and Neuroglial Cells Neurons: Generate, conduct, and receive nerve impulses (electrical signals). Amitotic Neuroglial cells Cell body Axon Dendrites Supportive cells that anchor neurons and blood vessels in place, speed up the rate Large center with the Moves impulse to the Arms that receive of nerve impulse transmission, and circulate fluid around the brain and spinal cord nucleus and organelles target cell messages - Neuroglial cells can divide by mitosis Tissue repair: process of wound healing; occurs differently in different tissues and is dependent on the tissues ability to regenerate Regeneration (Damaged or dead cells are replaced with cells of the same type). Fibrosis (Fibroblast divide by mitosis and produce collagen to fill in the defect left by the injury; 1. Cell Type: Tissues with high regenerative capacity, such as epithelial tissues (skin, gastrointestinal results in scar tissue, which is dense irregular connective tissues). lining) and some connective tissues (liver, bone), are more likely to regenerate. 1. Severe Injury: Extensive damage to tissue structure and the ECM can make regeneration difficult, 2. Extent of Damage: Regeneration is more likely when the damage is not extensive, and the tissue leading to fibrosis. architecture is minimally disrupted. 2. Chronic Inflammation: Prolonged or chronic inflammation can lead to excessive deposition of 3. Presence of Stem Cells: Tissues with abundant stem cells or progenitor cells can regenerate collagen and other ECM components, resulting in fibrosis. effectively. For example, skin and liver tissues have significant regenerative potential due to their 3. Lack of Regenerative Capacity: Some tissues, such as cardiac muscle or nervous tissue, have stem cell populations. limited regenerative capacity and are more prone to fibrosis following injury. 4. Minimal Scarring: When the 4. Disruption of ECM: Significant underlying extracellular matrix damage to the ECM can interfere (ECM) is intact and not excessively with the ability of tissues to damaged, regeneration can occur regenerate normally, favoring scar with less fibrosis. formation instead. The integumentary system: consists of the skin and its accessory structure. Including hair, nail, and glands The skin (cutaneous membrane) – largest organ in the body, making up 10-15% of our total body The skin has two main components: Superficial epidermis Deep dermis Keratinized stratified squamous epithelium resting on a basement membrane Consists of loose connective tissue and dense irregular connective tissue Accessory structures: nail, hair, sweat glands, oil-producing Sebaceous glands Epidermis is avascular, superficial layers is dead cells while dermis is vascularized Skin: sensory neurons and receptors, and arrector pili muscles that attach to hair Below dermis is the hypodermis (Superficial Fascia/Subcutaneous Tissue) which is NOT part of the skin; Includes loose connective/adipose tissue, highly vasculari. Function of the integumentary system (1) Protection (2) Thermoregulation (3) Sensation (5) Synthesis of vitamin D Mechanical Trauma Maintenance stable internal body temperature Sensory receptors in the skin are perceived as Required for calcium absorption, which is needed Such as stretching, pressure, or abrasion (negative feedback loops) sensations by the nervous system for nerve and muscle function, bone building and Pathogens Body temperature rises above normal Detects potentially harmful stimuli which is crucial maintenance, and other processes Disease-causing microorganisms Stimulus: Body °C increases to homeostasis Precursor compound of Vitamin D is in the Environment Receptor: Thermoreceptors in the brain detect the increased deep cells of the epidermis body °C Protects against environmental threats (4) Excretion When exposed to U V radiation, this Control Center: The heat-loss center in the hypothalamus of Skin absorbs ultraviolet (U V) radiation from the the brain receives the signal Small amounts of metabolic waste products, compound is converted to Cholecalciferol, sun before it damages underlying tissues; Secretes Effector/Response: Neurons stimulate sweating & dilation of including lactic acid and urea, are eliminated in which enters the bloodstream lipid-based chemicals that repel water and salts blood vessels in skin to release heat sweat Modified by the liver, then kidneys to form Return to Normal Range: Heat-loss center stops response which prevents water entering or leaving the body Small but significant contribution Calcitriol when body °C returns normal through the skin Epidermis: superficial part of the skin; composed of several cell types and up to 5 layers or Strata Keratinocytes Dendritic (Langerhans) Cells Makes up around 95% of cells in the epidermis; provides strengths to the Phagocytes of the immune system that protect the skin and deeper tissues epidermis Tactile (Merkel) Cells Manufacture Keratin, which is a fibrous protein that makes tissue strong and Sensory receptors that detect light touch and differentiate shapes and textures; Numerous in fingertips, lips, and the base of hairs resistant to mechanical stress, aids in waterproofing, immune response, barrier Melanocytes formation. Produce melanin, which is an orange red to brown-black pigment (discussed in Module 5.4) Thick and thin skin Thick Skin: Found on locations subject to more mechanical stress (palms of the hands, palmar surfaces of fingers, soles of the feet, and plantar surfaces of toes) Contains all 5 strata and a very thick stratum corneum Lacks hair follicles, but has numerous sweat glands Thin Skin: Found on remainder of body No stratum lucidum and thinner stratum corneum Includes hair follicles, sweat and sebaceous glands Callus Additional layers of stratum corneum; Forms in response to repeated pressure The dermis: Deep part of the skin; houses blood supply of the epidermis; contains sensory receptors; anchors the epidermis in place; divided into 2 layers Papillary layer: Superficial layer of the dermis Dermal Papillae: Reticular Layer: Deep layer of the About 20% of the depth of the dermis Provide blood supply to the epidermis dermis Made of loose connective tissue House Tactile (Meissner) Corpuscles, which Made of dense irregular connective At the dermis-epidermis junction, special collagen respond to light touch, and distinguish shape and tissue, which strengthens the dermis fibers extend into the basement membrane to anchor texture of objects; Numerous in fingertips, lips, face, and allows it to stretch, and house the epidermis; Repetitive trauma disrupts these fibers and external genitalia Blood vessels, sweat glands, hairs, and causes a fluid-filled pocket called a blister sebaceous glands, and sensory The surface of the papillary layer folds into projections receptors. that push into the epidermis called Dermal Papillae Skin markings: interaction between the epidermis and dermis are visible as small lines in the epidermis Most obvious are on the thick skin; Dermal papillae are prominent and arrange into Dermal Ridges The epidermis then indents to produce epidermal ridges that occur in patterns unique to each individual; Sweat pores open along these ridges and leave a fingerprint on surfaces Gaps between collagen bundles in the reticular layer form Tension, or cleavage Lines Run in a circular pattern in the neck and trunk and longitudinally in the head and limbs Flexure line are deep creases found on areas such as the palms Melanin: produces in vesicle called melanosomes, in melanocytes, the enzyme tyrosinase joins 2 molecules of the amino acid tyrosine to form melanin - Melanosomes migrate to the Melanin tips of the melanocyte and are Melanin synthesis increases on exposure to UV radiation taken into the keratinocyte by Immediate Effects Secondary Effects phagocytosis Oxidize the melanin, which darken Damage DNA of melanocytes, ↑ melanin production - Melanin is transported to the Melanin also decreases the synthesis of vitamin D to control the amount and keep it within a specific range area superficial to the nucleus, – Individuals living in Africa have darker skin to prevent excess vitamin D production, while people in northern where it shields the DNA from UV Europe have lighter skin to synthesize more vitamin D radiation, although it is not Common variations of pigmentation: complete protection – Freckle: Small area of increased melanin production in a local spot Melanin degrades after a few days, so – Mole (Nevus): Area of increased pigmentation, caused by local proliferation of melanocytes it must be replaced – Albinism: Melanocytes fail to manufacture tyrosinase; Results in lack of skin pigmentation and greatly increased the risk of keratinocyte D N A damage from U V radiation Accessory structure of the integument: hair, nails and glands - All are derived primarily from the epithelium Each structure assists the integument in performing overall function Hair, nails, sweat glands & sebaceous glands Hair or Pili: small, filamentous structure that project from all surface s of the skin except the regions with thick skin, the lips and parts of the genitalia Consists of squamous keratinized epithelial cells Function in protection Function in sensation: Hair around eyes/nose keep out foreign objects, hair on head protects against UV Sensory neurons associated with hair detect environmental changes Hair structure Hair shaft: Project from the skins surface and each strand has 3 regions Hair root: Portion embedded in the dermis Medulla Cortex Cuticle Arrector pili Hair bulb Present in thicks hairs only; Several layers of keratinocytes Single layer of keratinocytes with attach to the dermal root sheath and contract Enlarged area at the base of the root with a include soft keratin in the core, with hard keratin hard keratin; wears over time causing Piloerection, which causes “goosebumps” projection called the Hair Papilla, which supplies similar to that in the epidermis producing “split ends” capillaries to the root Hair Growth—grows at different rates for different individuals, averages about 1-1.5 cm per month Growth Stage and Resting Stage Alopecia Male and Female Pattern Baldness Growth and resting stages vary among individuals and hair types and determine maximal hair length Baldness caused by the death of hair follicles Baldness caused by hormones, particularly testosterone Hair pigment and texture Lanugo Terminal hair Vellus hair (peach fuzz Hair Color Red Hair Age Nonpigmented hair that covers Thick, coarser, and pigmented Thin, nonpigmented hair found Determined primarily by the Special reddish pigment that Melanocytes in hair produce less the body in a fetus; Falls out hair found on the scalp and on the rest of the body; After amount of melanin produced by contains the reddish form of melanin as we age, turning the after birth around the eyes puberty, much of the vellus hair melanocytes melanin (pheomelanin) and was hair gray or white is replaced by terminal hair but - Blonde hair melanocytes also found to contain ions the amount differs by sex: produce little melanin M: 90% vellus hair replaced Black hair melanocytes produce F: 35% vellus hair is replaced more melanin Nails—Hard structures located at the end of digits; Safeguard fingertips and act as tools (Consist of stratified squamous epithelium and hard keratin) Nail Plate: Portion of the nail that sits on top of the epidermal Nail bed divide into: Nail body Nail root Visible portion of the nail plate Portion of the nail plate under the skin with the nail matrix with actively dividing cells Nail Growth is continuous with fingernails growing about 0.5 mm per week, while toenails grow more slowly Keratinocytes die as they move away from the matrix Nail Pigment Nails contain no melanocytes, so they are translucent with an opaque half-moon shaped region near the proximal nail fold called the Lunula, which has accumulated more keratin. Nail beds are pinkish is a well-oxygenated individual and bluish (cyanotic) in a poorly oxygenated individual Sweat (sudoriferous) glands: all (4) types of sweat glands release their various products by exocytosis, a type of secretion called Merocrine Secretion (1) Eccrine Sweat Glands (2) Apocrine sweat glands (3) Ceruminous Glands—Modified apocrine glands that secrete Most prevalent sweat gland Large glands in the dermis, found only in the axillae (armpits), anal thick Cerumen (ear wax) - Sweat exits through a duct with a sweat pore in the epidermis area, and areolae (darkened area around the nipples) - Secreted onto hair follicles to protect and lubricate the - Eccrine sweat is 99% water with small amounts of electrolytes - Sweat exits onto a hair follicle rather than through a pore tympanic membrane, or eardrum, of the ear and waste products - Apocrine sweat is thick and rich in proteins (4) Mammary Glands Primary function is thermoregulation - When secreted, the sweat is odorless, but when metabolized by Highly specialized sweat glands that produce modified sweat : milk bacteria, it produces odor Milk contains proteins, lipids, sugars, and other substances to Secretion begins at puberty with influence from hormones nourish a newborn infant Sebaceous Glands Acne Vulgaris or Acne Wound Branched glands with clusters of secretory cells Caused by an accumulation of sebum and dead cells within the Common skin pathology defined as any call Acini that surround small ducts that usually sebaceous glands producing a Comedone, or Blackhead disruption in the skin’s integrity empty onto a hair follicle If these become infected with the bacterium Propionibacterium acnes, Wounds may involve the inflammation and formation of a Pustule, or Pimple may occur and may epidermis, the dermis, and lead to scars occasionally deeper tissues Burns—Skin wound caused by agents such as heat, extreme cold, electricity, chemicals, and radiation First degree burns: Superficial burns Second degree: Partial thickness burns Third degree Full thickness burns - Only epidermis is damaged - Epidermis and part of the dermis are damaged - Epidermis, dermis, hypodermis, and possibly - Erythema and minor pain are present, but no - Significant pain, blistering, and possibly deeper tissues are damaged blisters or permanent damage occur scarring occur - Not painful initially because of nerve damage, - No treatment is usually required - Treatment is usually required but major tissue damage and significant scarring occur - Problems with dehydration due to massive fluid loss and infection are serious complications Treatment may require extensive skin grafting, which involves transplanting skin from another part of the body onto the wound Rule of Nine: Burns Second and third-degree burns can be described by estimating the percentage of body Skin Cancer surface they affect using the rule of nine Cancer: Mutations in a cell’s D N A induce the cell to lose control over the cell cycle - Divides body into 11 areas, each representing 9% of total body surface area (genital resulting in a Tumor, or cluster of undifferentiated cells area is 1%) Cancerous tumors prevent the tissue from functioning normally, and can - A burn involving the entire right lower limb covers 18% of the body Metastasize, or spread to other tissues - Used to estimate how much fluid to give burn patients Skin Cancer—Linked to exposure to U V radiation, and other cancer-causing - Must be modified if body proportions are different agents, called Carcinogens Three common skin cancers include: Basal Cell Carcinoma, Squamous Cell Carcinoma, and Malignant Melanoma THE SKELETAL SYSTEM (Includes the bones, joints, and other supporting tissues) Bones - Main organs of the system; Adults typically have 206 bones. Each bones includes: Bone (osseous) tissue Dense regular collagenous tissue Dense irregular connective tissue A tissue called Bone Marrow Functions of the Skeletal System (6) (1) Protection (3) Mineral storage and acid base homeostasis (4) Blood cell formation (6) Movement Bones such as the skull, sternum, and ribs protect Bone stores minerals including calcium, Red Bone Marrow in bones is the site of Bones are the sites of attachment for most skeletal underlying organs phosphorus, and magnesium salts; These minerals hematopoiesis or formation of blood cells muscles; when muscles contract, they pull the (2) Support are electrolytes, acids, and bases in the blood, and (5) Fat storage bones which generates movement around a joint The skeleton supports the weights of the body and are critical for electrolyte and acid-base Yellow bone marrow in bone contains adipocytes provides its structural framework maintenance with stored triglycerides Classification of bone by shape Long Bone Short Bone Flat Bones Irregular Bones Sesamoid Bones Longer than wide; About as long as wide or Thin and broad; Examples Irregular shapes; Small, flat, oval-shaped Examples include bones of roughly cube-shaped; include most of the skull Examples include the bones located within the limbs; Some long Examples include the wrist bones and bones of the vertebrae tendons; An example is the bones are very small and ankle bones pelvis kneecap Structure of a Long Bone Periosteum Perforating Fibers Diaphysis Epiphyses Compact Bone Spongy (Cancellous) Epiphyseal Lines Outer dense irregular Collagen anchors that Shaft of the bone with Ends of a long bone Hard, dense outer Bone Remnants of an connective tissue penetrate into bone a medullary (marrow) (filled with Red bone that resists linear Inner, honeycomb-like Epiphyseal (Growth) membrane with blood matrix to attach the cavity lined by the Marrow) covered with compression and bone framework that Plate, which is a line of vessels and nerves periosteum Endosteum (A Articular Cartilage, twisting forces resists forces in many hyaline cartilage membrane lining the which is composed of directions and actively growing in inner surface of the hyaline cartilage provides a place for children and bony wall) and filled bone marrow to reside adolescents with marrow Structure of Short, Flat, Irregular, and Sesamoid Bones Share similarities with long bones, but have fewer structures In flat bones, the spongy bone is called diploë and in some flat and irregular bones of the skull, there are air-filled spaces called sinuses to make the bones lighter Blood and Nerve Supply to Bone Bones are well supplied with blood vessels and many sensory fibers – Blood supply to long bones is from the periosteum and 1 or 2 Nutrient Arteries that enter through a small hole in the diaphysis called the nutrient foramen to supply the internal structures of the long bone – Blood supply to short, flat, irregular, and sesamoid bones is provided mostly by vessels in periosteum that penetrate bone Red and yellow marrow Yellow Bone Marrow Red Bone Marrow Consists mostly of blood vessels and adipocytes. (Can make cartilage, bone or during Network of reticular fibers supporting islands of hematopoietic cells (where red blood cells , white blood cells and platelets form) life threatening emergencies can turn to red bone marrow to produce blood cells) – Infants and young children have mostly red bone marrow because of their rapid growth rate, which begins to change to yellow marrow at about age 5-7 – Adults have mostly yellow marrow with red marrow found mostly in flat bones such as the hip bone, sternum, skull, vertebrae, ribs, shoulder blades and ends of long bones. The Extracellular Matrix of Bone Inorganic Matrix—About 65% of bones total weight Organic Matrix (Osteiod)—About 35% of bones total weight Figure 6.5 The importance of bone matrices. Consists mostly of calcium salts and phosphorus as part of – Consists of protein fibers (mostly collagen), proteoglycans, a large mineral called hydroxyapatite glycosaminoglycans, glycoproteins, and bone-specific Ca10(PO4)6(OH)2 which gives bone its hardness and proteins such as Osteocalcin ability to resist compression and bending – Collagen helps bone resist torsion (twisting) and tensile (pulling Bicarbonate (HCO3-), potassium, magnesium, and or stretching) forces that would cause breaks in bones, and sodium salts are also in the inorganic matrix aligns with hydroxyapatite crystals to enhance bone hardness Bone Cells: Bone is dynamic tissue because new bone is continually being formed as older bone is broken down Osteoblasts build bone and matures into; Histology of bone Spongy bone Osteocytes which maintain bone Compact bone Resists forces from many directions and forms a Osteoclasts break down bone Hard, dense, outer shell, able to resist a great amount of stress that would typically strain or deform an object protective framework for the bone marrow – Units are called osteons or Haversion Systems although not weight bearing Osteon structure – Organized into branching “ribs” of bone called trabeculae Lamellae (Concentric Central (Haversian) Canal Lacunae Trabeculae—Covered with endosteum; Contain Lamellae) Contains blood vessels and Small cavities between lamellae concentric lamellae, houses osteocytes; Access Rings of very thin layers of bone; nerves; Lined by endosteum filled with E C F; About 20,000– blood supply from blood vessels in bone marrow Osteons contain 4 to 20 lamellae; 30,000 osteocytes and lacunae Collagen fibers of adjacent are found in each cubic lamellae run in opposite millimeter of bone directions which resists twisting and bending forces Osteoporosis and Healthy Bone Tissue Osteoporosis—Bone disease caused by inadequate inorganic matrix in the E C M Makes bone brittle and increases the risk of fractures, which also heal more slowly Note the differences in healthy versus osteoporotic bone (right) Causes of Osteoporosis Dietary factors, such as calcium ion and vitamin D deficiency; Female sex; Advanced age; Lack of exercise; Hormonal factors, such as lack of protective estrogen in postmenopausal women; Genetic factors; Diseases of the skin, digestive and urinary systems Preventative Measures and Treatments Ensure adequate intake of calcium and vitamin D; Engage in weight-bearing exercises; Replace estrogen, if appropriate; Use drugs that inhibit osteoclasts or stimulate osteoblasts Bone growth in length - Longitudinal Growth—Lengthening of long bones when chondrocytes divide at the Epiphyseal Plate The epiphyseal plate has 5 different zones of cells: 1) Zone of Reserve Cartilage 2) Zone of Proliferation 3) Zone of Hypertrophy and 4) Zone of Calcification 5) Zone of Ossification Cells not directly involved in bone growth, Chondrocytes are actively Maturation Dead chondrocytes matrix becomes Contains calcified chondrocytes but can divide if needed dividing lacunaue; most mitotic Contains mature chondrocytes calcified; Far from blood supply and osteoblasts to build bone activity Zones 2–5 are actively involved in longitudinal growth, and as cells divide, the cells “above” them progressively become part of the next zones Steps of Longitudinal Growth 1) Chondrocytes divide in the zone of proliferation 2) Chondrocytes that reach the next zone enlarge and mature (Lacuenae surrounding the chondrocytes are larger here) 3) Chondrocytes die and their matrix calcifies 4) Calcified cartilage is replaced with bone (In the zone of ossification, osteoblast invade the calcified cartilage and lay down bone; osteoclast resorb the calcified cartilage/bone which is replaced by bone) Bone Growth in Length Longitudinal growth continues at the epiphyseal plate as long as mitosis is happening in the zone of proliferation At about 12–15 years of age, the rate of mitosis slows, but ossification in steps 3 and 4 continues which causes the epiphyseal plate to shrink until the zone of proliferation is overtaken by the zones of calcification and ossification When the zone of proliferation completely ossifies (between ages 13 up to 21), the plate is said to be “closed” and leaves a remnant called the epiphyseal line 6.4 Bone Growth in Width Appositional Growth—Growth of all bones in width; May continue after bone growth in length ceases Osteoblasts between the periosteum and the bone surface lay down new bone Begins with the formation of new circumferential lamellae; As new lamellae are added, the deeper circumferential lamellae are removed or incorporated into osteons Primarily thickens the compact bone of the diaphysis; Osteoclasts in the medullary cavity digest the inner circumferential lamellae so as bones increase in width, their medullary cavities enlarge as well Gigantism and Acromegaly Gigantism—Excess growth hormone is secreted in childhood before the closure of the epiphyseal plates Excessive longitudinal and appositional growth occurs Acromegaly—Excess growth hormone is secreted after closure of the epiphyseal plates Results in enlarged bones of the skull, face, hands and feet, and soft tissues such as the tongue Can cause heart and kidney malfunction and diabetes mellitus Both gigantism and acromegaly are generally treated by removing a tumor that secretes growth hormone Bone remodeling: the continual process of bone formation, by Bone Deposition, and bone loss, by Bone Resorption. Occurs for many reasons: : Maintenance of calcium ion homeostasis Bone repair Replacement of primary bone with Replacement of older, brittle bone, with Bone adaptation to tension and secondary bone newer bone stresses Bone Remodeling in Response to Tension and Stress Bone Remodeling in Response to Tension and Stress In healthy adult bone, bone formation and bone loss The heavier the load a bone carries, the more bone tissue is deposited in that bone occur simultaneously by osteoblasts and osteoclasts, respectively Tension Pressure In children, bone formation outweighs bone loss Stretching force; Stimulates bone deposition Application of a continuous downward force; Stimulates bone resorption Other factor influencing bone remodeling (1) Age (2) Hormones (4) Vitamin D Intake (5) Vitamin K Intake Hormone levels decline with advancing age, such as Testosterone strongly promotes bone deposition, Promotes calcium ion absorption in the intestines Required for osteocalcin to bind to calcium ions; growth hormone, which causes a reduction in protein while estrogen depresses osteoclast activity and prevents calcium loss in the urine; Inadequate Promotes proliferation of osteoblasts, increases synthesis, and estrogen, which reduces the protective (3) Calcium Ion Intake amounts in children causes Rickets, which results their lifespan, and causes them to deposit more effects of the hormone on bone remodeling Required for bone deposition in bone deformities, fractures, and muscle matrix; Inhibits osteoclast division and activity weakness Bone repair: steps of fracture healing 1) A hematoma fills the gap between the bone 2) Fibroblasts and chondroblasts infiltrate 3) Osteoblasts build a hard (bone) callus. 4) The bone callus is remodeled, and fragments (Hematoma—Ruptured blood vessels that the hematoma, and a soft callus form (Over several weeks, osteoblasts from the primary bone is replaced with secondary bleed into the injured site.) (Fibroblasts form dense irregular periosteum lay down a collar of primary bone bone. (Over several months, the primary connective tissue and chondroblasts secrete called a bone callus) bone is resorbed and replaced with hyaline cartilage; These 2 components secondary bone; The bone callus often produce the soft callus) remains visible following full healing of the injury) Classes of fractures Treatment of fracture: Stabilization of the fracture, followed by immobilization for about 6 weeks Simple (closed) fractures Compound (open) fractures Closed reduction Open reduction Skin and surrounding tissue remain impact Damage around the fracture Bone ends are brought into contact Surgically fixated with plates, wires, and/or screws The skeleton: include approximately 206 bones and associated skeletal cartilages Skull: The The skeleton’s most complex structure with 22 bones; 8 cranial bones encase the brain; 14 facial bones form the framework for the face Vertebral column Thoracic (Rib) Cage Pectoral Girdle Upper Limb Pelvic Girdle Lower Limb Includes 33 vertebrae; The top 24 Includes 12 pairs of ribs, the Includes the clavicle and scapula; Arm includes humerus; forearm Includes pelvic bones and the The thigh includes the femur; vertebrae encase the spinal cord; sternum, part of the vertebral Supports the upper limb and includes the radius and ulna; The sacrum; Each pelvic bone is The leg includes the tibia and The inferior bones, the sacrum column; Protect the structures in anchors it to the trunk wrist includes the carpals; The composed of an ilium, ischium, fibula; The ankle includes the and coccyx, are made of fused the thoracic cavity hand and fingers include and pubis; Supports the lower tarsals; The foot includes the vertebrae metacarpals and phalanges limb and anchors it to the trunk metatarsals and phalanges  Structural division of the skeleton Axial Skeleton Skull bones Longitudinal axis of the body; Structured for protection All skull bones are united in adults by immoveable joints called Sutures, except the mandible (lower jawbone) - Skull, vertebral column, thoracic (rib) cage Cranial Bones (Cranium) Neurocranium Appendicular Skeleton Single Bones—Frontal, Occipital, Ethmoid, Sphenoid Structured for motion Paired Bones—Temporal, Parietal Pectoral girdle, upper limbs, pelvic girdle, lower limbs Facial Bones Viscerocranium Single Bones—Mandible, Vomer Paired Bones—Maxilla, Zygomatic, Nasal, Lacrimal, Palatine, Inferior Nasal Concha Figure 7.5 Anterior view of the skull. Figure 7.6 Lateral view of the skull. Figure 7.2 Basic structure of the skull: Figure 7.10 Disarticulated skull anterolateral view of the cranial and facial bones The orbit Paranasal sinuses Houses the eyeball, its associated blood vessels, muscles, and nerves, and Paranasal Sinuses Hyoid Bone the lacrimal gland, Found within the Small, C-shaped bone which produces tears frontal, sphenoid, suspended in the superior neck Formed by 7 bones: ethmoid, and by muscles and ligaments 1. Frontal maxillary bones Attachment points for muscles involved in swallowing and 2. Maxilla Lined with speech 3. Zygomatic, mucous 4. Sphenoid, membranes 5. Ethmoid, and connect to 6. Lacrimal the nasal 7. Palatine cavity Lighten the skull and enhance voice resonance Infections result in sinusitis Oral Cavity—Houses the teeth, the tongue, and some salivary glands; First part of the gastrointestinal tract of the digestive system Vertebral Column (Spine) —Average of 33 Vertebrae 7 cervical 12 thoracis 5 lumbar 5 fused sacral (sacrum) 3-5 fused coccygeal (coccyx) C1-c7 located in the neck T1-T12 articulate with the ribs L1-L5 located in the lower back Articulate with the pelvic bones Located at the most inferior end of the vertebral column Spinal curvatures Primary (Thoracic and Sacral)—Present during fetal period Secondary (Cervical and Lumbar) —Develop after fetal period Sacral curvature Thoracic curvature Cervical Curvature Lumbar curvature Convex; lumbosacral junction- coccyx Convex Concave Concave Bones of the Hand and Fingers: Metacarpals and Phalanges Sacrum and Coccyx Manus (Hand) - Sacrum- s1-s5 form the posterior wall of the Includes the metacarpal bones, which are numbered I–V. pelvic activity. Fuse by ages 20-25 Fingers Coccyx- generally composed of 4 vertebrae: fuse about Includes 14 total phalanges age 25 Thoracis cage – Ribs: include Includes 12 pairs of ribs and Costal Cartilages, made of hyaline cartilage which provides flexibility; Spaces between ribs are the Intercostal Spaces - Ribs 1–7- True (vertebrosternal) ribs; Attach to the sternum via their own costal cartilage. - Ribs 8–12- False (vertebral) ribs; Do not attach to the sternum directly Ribs 8–10 Ribs 11–12 Vertebrochondral ribs: Costal cartilages attach to the cartilage of rib 7 as the Floating ribs: Do not attach to the sternum. Costal Margin. The pectoral girdle: The humerus: Consists of two bones, the Clavicle and Scapula, that support the upper limb only bone of the arm (branchium) 1. Clavicle—S-shaped bone; – Functions like a brace for the upper limb so that it rests laterally to the trunk 2. Scapula—Sits on the posterosuperior rib cage; Injuries to the A C joint are common and are referred to as a separated shoulder Bones of the forearm: the radium and Ulna Forearm (Antebrachium) Crossing of the radius and ulna the elbow joint Consists of a lateral Radius and a medial Ulna - Ulna—Proximal epiphysis - The proximal radius and ulna fit with the distal humerus to form the elbow joint Radius Proximal epiphysis is the Radial Head that articulates with the capitulum as part of the elbow joint and with the ulna to form the proximal radioulnar joint; The pelvis and bones of the pelvic girdle Pelvis Female and Male Pelvis Consists of two pelvic bones, the sacrum, which form the oval-shaped Female pelvis is generally wider, shallower, lighter, and less Pelvic Inlet with the robust than the male pelvis surrounding bony ridge Shape of Greater Pelvis – Wide in females and anterior called the Pelvic Brim, superior iliac spines are far apart with flared iliac crests; and the coccyx Narrow in males, anterior superior iliac spines are close - Pelvic bone is together, iliac crests are straight composed of three Coccyx and Sacrum – Male sacrum is longer and narrower bones: Ilium, than the female sacrum; Female coccyx is situated more Ischium, and Pubis posteriorly and is more moveable than the male coccyx Pelvic Inlet and Outlet – Female pelvic inlet is wide and oval; Male pelvic inlet is narrow and heart-shaped; The male pelvic outlet is narrower than that of the female Bones of the Thigh: The Femur and Patella Bones of the Leg: The Tibia and Fibula Bones of the Ankle and Foot: The Tarsals, Metatarsals, and Phalanges Femur Leg Foot Only bone of the thigh Consists of a medial Tibia and a lateral Fibula held together by an - Tarsals (7) - Largest and strongest bone in Interosseous Membrane - Metatarsals (I–V). the body Tibia – Second strongest bone in the body Toes Patella Fibula - Includes 14 total phalanges - Sesamoid bone The knee joint consists of two articulations – tibiofemoral and patellofemoral. The joint surfaces are lined with hyaline cartilage and are enclosed within a single joint cavity Muscle Tension Properties of Muscle Cells Generation of force by all muscle tissue; creates movement, maintains posture, Contractility: Ability to contract where proteins in the cell draw closer stabilizes joints, generates heat, and regulates the flow of materials through together hollow organs Excitability: ability to respond to a stimulus (chemical, mechanical or - Muscle tissue consists of Muscle Cells (Myocytes) and the surrounding electrical) extracellular matrix called Endomysium, which holds the muscle cells Conductivity: ability to conduct electrical charges across the plasma together and transmits tension to neighboring cells membrane - Muscle types include skeletal, cardiac and smooth Distensibility: ability of a cell to be stretched without being ruptured (Myo=muscles Sarco=flesh) Elasticity: ability of a cell to return to its original length after it has been stretched Gross Anatomy of a Skeletal Structure of Muscle Cells Muscle Muscle cells have most of the same organelles as other cells, but there are structural differences: Skeletal muscle cells are Sarcoplasm The Sarcolemma The muscle Myofibrils Bundles of specialized called Skeletal Muscle Fibers muscle cell’s cytoplasm cell’s plasma membrane proteins, including those involved in because of their long, thin muscle contraction shape; surrounded by a thin Composed of hundreds to thousands of protein bundles called Myofilaments. Many myofibrils layer of extracellular matrix come together to make up a myocytes called endomysium Myofibrils consist of: Between 10 and 100 muscle Contractile Regulatory Proteins Structural Proteins cell fibers are bundled together into a group called a Fascicle, which is surrounded by Proteins Control when the muscle Hold the myofilaments in proper connective tissue called perimysium Produce tension fiber can contract places, ensure stability of muscle fiber All fascicles in muscle surrounded by another layer of connective tissue epimysium 3 types of myofilaments: Thick Filaments, Thin Filaments, and Elastic Filaments Epimysium is continuous with the most superficial connective tissue sheath, known as Sarcoplasmic reticulum (SR) is a modified smooth endoplasmic reticulum that forms a weblike the Fascia network surrounding each myofibril Thick Filaments Phases of skeletal muscle contraction Largest diameter; composed of the contractile protein myosin Excitation Phase The sarcolemma of a muscle fiber must be stimulated by ACh from a motor - Each myosin molecule includes two globular “heads” and two intertwining chains making up a neuron to have an action potential “tail”; the heads protrude from the myosin tail. Excitation Contraction Coupling Phase—Transmits the excitation to the parts of the fiber that Thin Filaments produce the contraction, the myofilaments, via calcium ions from the S R Made up of contractile, regulatory, and structural proteins: Contraction Phase Sliding-filament mechanism occurs and the sarcomere contracts Actin Bead-shaped protein with an active site that can bind to a myosin head. Muscle contraction: each sarcomere shortens a little Tropomyosin Long, rope like regulatory protein that spirals around the two actin strands so that, at rest, Basic process of contraction it covers the active sites on actin. 1. Skeletal muscle must be activated by a nerve. Troponin Small, globular regulatory protein that consists of subunits that hold the tropomyosin in place; 2. Nerve activation increases the concentration of Ca²⁺ ions in the vicinity of the contractile proteins. together, tropomyosin and troponin help to switch on and off muscle contraction. 3. The presence of calcium ions enables contractions. Elastic Filaments 4. When nerve stimulation stops, contraction stops. Thinnest filaments; composed of a single massive structural protein called Elastic Filaments which is Nerves Activate Skeletal Muscles shaped like a spring Motor neurons stimulate muscle contraction. Uncoils when stretched and recoils when the Acetylcholine (neurotransmitter) is released from motor neuron at neuromuscular junction. stretching force is removed. Also resist Acetylcholine diffuses across neuromuscular junction to muscle cell receptors. excessive stretching and provide elasticity to Binding of acetylcholine to muscle cell receptors generates electrical impulse within muscle cell. the muscle fiber to help it “spring” back to its Electrical impulse is transmitted through the cytoplasm. original length after it is stretched Z-Lines: attachment points for sarcomeres (A Activation Releases Calcium sarcomere is a segment of myofibril extending from - Activation Releases Calcium one Z-line to the next) - Calcium is released from sarcoplasmic reticulum - Ca++ initiates chain of events that cause contraction when it contact the myofibrils Contraction Phase: The Crossbridge Cycle of the Sliding-Filament Mechanism-Preparation 1) Calcium ions bind to troponin 2) Tropomyosin moves, and the active sites of actin are exposed Myosin heads then bind to the active sites of an actin subunit, which is known as a Crossbridge initiating a Crossbridge Cycle; muscle Contractions are a series of crossbridge cycles and the resulting tension Contraction Phase: The Crossbridge Cycle of the Sliding-Filament Mechanism- Contraction 1) ATP hydrolysis (the breakdown of ATP) excites the myosin head Myosin heads contain sites that bind to ATP and an ATPase enzyme that catalyzes the breakdown of A T P; when A T P binds to the myosin head, the A T Pase catalyzes the hydrolysis of A T P to A D P and a phosphate group (P); energy liberated from this reaction excites the myosin head into its high-energy position, ready to work 2) The myosin head binds to actin The resulting crossbridge is at about a 90-degree angle 3) The power stroke occurs when the phosphate and ADP detaches from the myosin head and myosin pulls actin toward the center of the sarcomere As the myosin pivots, it pulls the actin toward the center of the sarcomere in the action known as the Power Stroke; myosin crossbridge is at a 45degree angle 4) A T P breaks the attachment of myosin to actin ATP attaching to myosin relaxes the head and it lets go of actin. The contraction cycle is repeated; A T P is hydrolyzed, the myosin head is reexcited, it binds to the next actin subunit, and the power stroke repeats For the average contraction, this process repeats about 20–40 times for each myosin head in each sarcomere of the muscle fiber Glycolytic (Anaerobic) Catabolism Oxidative Energy Sources Series of reactions that take place in the cytosol that split a six-carbon Oxidative (Aerobic) Catabolism—Series of reactions that take place in glucose molecule into two three-carbon pyruvate molecules; produces two mitochondria where electrons are removed from carbon-based net A T P compounds, and energy liberated is then used to fuel synthesis of ATP Glycolysis can provide adequate A T P for only about 30–40 seconds Provides sustained muscle activity beyond short bursts of activity; of sustained muscle contraction produces more A T P than glycolysis Requires no oxygen directly, but the fate of the two pyruvate Muscle fibers can use multiple fuels including the products of molecules depends on the availability of oxygen glycolysis, as well as fatty acids and amino acids, although glucose If oxygen is abundant, pyruvate enters the mitochondrion for will be used first oxidative catabolism. Can provide ATP for hours, as long as oxygen and fuels are available; after 1 minute of muscle If oxygen is not abundant, pyruvate is converted into two molecules of the compound lactic acid activity, this is predominant source of ATP and after several minutes, provides 100% of the ATP Figure 10.21b Sources of energy for muscle fibers. Muscle Twitch Response of a muscle fiber to a single action potential in a motor neuron; smallest muscle contraction Only occur in a laboratory with direct electrical stimulation of a muscle fiber, not in whole muscles in the body Twitches can create different amounts of tension, both within an individual muscle fiber and within an entire muscle Muscle Fatigue Defined as inability to maintain a given level of intensity of a particular exercise; results from a combination of several factors, which may include: Depletion of key metabolites Decreased availability of oxygen Accumulation of certain Environmental conditions to muscle fibers chemicals Many other causes, such as psychological factors, other physiological factors from other body systems may also be involved in muscle fatigue Smooth Muscle Contraction and Relaxation - Consumes as little as one-one hundredth of the A T P used by skeletal muscle fibers while still generating significant force, as the crossbridge are attached much longer than in skeletal muscle fibers Cardiac Muscle Contraction and Relaxation Pacemaker cells rhythmically and spontaneously generate action potentials allowing cardiac muscle tissue to be Autorhythmic