Lecture 7: Integument - Biology Notes PDF

Lecture 7: Integument Main Idea: Integument - Skin, Hair, Nails, Glands Skin: - 2 main regions: - Epidermis: > Outermost layer, composed of epithelium > Avascular (No blood flow) > Protects underlying layers - Dermis: > The underlying layers...

Lecture 7: Integument Main Idea: Integument - Skin, Hair, Nails, Glands Skin: - 2 main regions: - Epidermis: > Outermost layer, composed of epithelium > Avascular (No blood flow) > Protects underlying layers - Dermis: > The underlying layers > Vascular and innervated > Contains smooth muscles (associated with hair follicles) and nerve fibers to detect and monitor sensory output + Subcutaneous layer: > Technically not part of the skin - consider it lowest underlying layer > Composed of areolar and adipose connective tissue > Acts as a shock absorber and insulator > Anchors skin to underlying structures Epidermis: - Consists of keratinized stratified squamous epithelium - Protects against foreign invaders due to dry surface - inhospitable to growth - Epidermis produces Vitamin D in the skin on exposure to UV light from cholesterol precursor, converted into active form by enzymatic reaction in liver and kidney, increases intestinal reabsorption of Ca2+ and and PO4 3- - Langerhans’ cell - epidermal dendritic (has tendrils) - found within strata spinosum and granulosum. Phagocytic - can stimulate immune response - Three innermost layers have living cells - two outermost have dead cells - Primary Cells: + Keratinocytes: Most abundant Produces keratin (fibrous protein that forms intermediate filaments) that provides protective properties of skin  Tightly connected by desmosomes + Melanocytes: Long, branching spider like processes Synthesize and store pigment of melanin in response to UV light Melanin granules are taken up by keratinocytes and accumulate on superficial side of nucleus to protect it from UV light - From deep to superficial: + Stratum Basale: Deepest layer Attached to a basement membrane that separates it from underlying dermis Epidermal ridges increase grip Single layer of cuboidal to low columnar cells - mostly keratinocytes, few melanocytes Tactile discs are merkel cells found here. Mechanoreceptors, small receptive fields. Response to tactile stimulation (fine touch, pressure) helps determine shape and texture of an object. Free nerve endings responsible for pain, sense light touch and noxious stimuli + Stratum Spinosum: Overlies stratum basale Several layers thick Keratinocytes from basale differentiate into non-dividing, specialized keratinocytes Attached by desmosomes, resulting in spiny appearance Epidermal dendritic cell found here + Stratum Granulosum: 3-5 layers thick Last living layer Site of keratinization: Keratinocytes produce keratohyalin granules - nucleus and organelles disintegrate, causing cells to die Keratinization complete when keratinocytes rise to superficial (stratum corneum) layer + Stratum Lucidum: Thin, clear, 2-3 layers thick Protects against friction Found only in thick skin on palms and soles Cells become flattened and featureless Filled with eleidin (intermediate protein formed by keratohyalin) during keratin maturation, helps protect skin from UV rays + Stratum Corneum: Most superficial Individual keratinocytes from deepest (stratum abseil) layer exists for about 4 weeks, lost due to desquamation Corneum is 15-30 layers of interlocked, dead, keratinized cells  Cells are now anucleate (without nucleus), tightly packed together with large amounts of keratin Forms a protective overcoat - has a thickened plasma membrane enhanced by glycoproteins, making it waterproof and insensitive to biological, chemical, and physical assault Thick vs. Thin Skin: - Thickness is determined by the number of layers in the epidermis + Thick: - 5 layers (includes stratum lucidum - clear layer) - Found on palms and soles - Contains sweat glands, but not sebaceous glands or hair follicles + Thin - 4 layers (does not include clear layer) - Covers most of body - Contains sweat glands, hair follicles, and sebaceous glands How Skin Color Protects You: - Melanin: Only pigment made in skin Delivered to keratinocytes within melanosomes Melanin pigment includes a variety of colors Eumelanin: Black-brown Pheomelanin: Red-yellow Everyone has relatively same amount of melanocytes - skin shade is reflective of amount of melanin produced and retained Freckles and moles are accumulated melanin - Carotene: Yellow/orange pigment found in certain plants Accumulates in stratum corneum (top layer) and fatty tissues of hypodermis Dermis: - Cells typical of those found in connective tissue proper - Richly innervated and vascularized - Possesses lymphatic vessels - Two layers:  + Papillary layer Located near the superior surface Areolar connective tissue Dermal papillae: small projections indented into epidermis - Contains capillary loops and free nerve endings (pain and touch receptors) - Interdigit with epidermal ridges to increase area of contact and interlock two layers + Reticular layer: Dense irregular connective tissue underlying the papillary layer of the dermis - mostly collagen fibers running parallel to skin surface, creates cleavage lines Highly vascularized and innervated Nerves allow us to distinguish sensory stimuli Blood vessels supply nutrients for dermis and epidermis, also help regulate temperature Possesses flexure lines - dermal folds where dermis is tightly secured to deeper structures Nails: - Scalelike modifications of stratum corneum, comprised of hard keratin - Protects the distal tips of digits and assists in grasping object - 3 Parts: + Nail Plate: - Top + Nail Bed: - Underlies nail plate + Nail Matrix: - Actively grows part of the nail - Produces nail bed + Other structures: + Lunula: White crescent at base of nail + Cuticle ‘Eponychium’: Thin strip of epithelium that protects the matrix Hair: - Flexible strands of dead keratinized cells produced by hair follicle. Hard keratin - tougher and more durable, so individual cells so not flake off - Shaft shape determines appearance of hair Ribbonlike: Kinky Round: Straight and coarse Oval: Wavy  - Hair pigment made in melanocytes found at base of follicle (Gray hair: Diminished melanin production White hair: No melanin production) - 3 types: + Lanugo: Fine, downy hair found on fetus (3rd trimester) + Vellus: Replaces lanugo hair - fine, pale body hair + Terminal: Darker, thicker hair found on head, axillary and pubic regions (face and chest of adult males), dependent on nutrition and hormones - Hair structure: + Shaft: Projects above skin surface, dead epithelial cells + Root: Lies below skin surface, dead epithelial cells + Hair bulb: Region at the base of hair follicle, deep in dermis, origin of hair and made up of living epithelial cells + Hair papilla: Capillaries supplying nutrients and nerves to hair - hair matrix contains cells that make up hair shaft, contains hard keratin proteins Medulla: Innermost portion, remnant of matrix, loosely arranged cells with air pockets and flexible keratin Cortex: External to medulla, several layers of flattened cells, hard keratin Outer layer consisting of a single layer of cells, overlapping one another away from root - Hair follicle: Folds down from epidermis into dermis. Follicle wall has two layers: Connective tissue root sheath from dermis and epithelial root sheath from epidermis. Arrector pili muscle responsible for contraction of hair follicle Hair function: - Protection: Head (sunburn and injury) Nasal and ear (traps particles) Eyes (prevent sweat and particles from endangering eye) - Heat retention Acts like cap to prevent heat escaping scalp - Sensory reception Tactile receptors detect light touch - Visual identification Determines age and sex, and identifies individuals - Chemical signal dispersion Pheromones in axillary and pubic regions Hair growth: Anagen: Active, produces new hairs Catagen: Regressive, involution of hair follicle Telogen: Resting phase, hair sheds Glands: - Sudoriferous glands (Sweat glands): Scattered all over body - Merocrine sweat glands: Eccrine glands > Abundant on palms, soles, forehead > Sweat - hypotonic filtrate of blood (99% H2O) > Functions: Thermoregulation, excretion (salts and urea), protection (antibacterial peptide) > Sympathetically regulated (Emotionally induced sweating) - Apocrine glands: > Structure: Located in axillary & anogenital regions, ducts empty into hair follicles > Secretions: Sweat, fatty substances, protein. Secretions are odorless but cause odor when broken down by bacteria > Function: Possibly equivalent of sexual scent gland - Sebaceous glands: > Secrete sebum, which kills bacteria, stimulated by hormones > Function as holocrine glands > Typically secrete into hair follicles > Secretions soften and lubricate hair and skin, prevent water loss and bacterial growth - Ceruminous glands: > Modified apocrine glands > Located in ear, produce cerumen (ear wax) to lubricate external auditory meatus and eardrum > Protects ear from foreign particles - Mammary glands: > Specialized sweat glands, secretes milk > Only functional in lactating females but present in both genders > Regulated by hormones Tissue Repair: - Two major methods: + Regeneration: Replaces destroyed tissue with the same tissue and restores organ function + Fibrosis: Binds damaged parts back together, replaces cells with collagen fibers resulting in scar tissue, no functional restoration - Type of restoration dependent on type of tissue damage and severity of injury - Both regeneration and fibrosis can appear in healing damaged skin - The rate of process is dependent on extent of damage - Four basic stages: 1. Inflammatory response: + Immunocytes attracted by chemical signals arrive at sight of damage + Cut blood vessel allows blood into wound + Clotting proteins and thrombocytes hold sides of the wound together 2. Clotting: + Clot stops blood flow and protects damaged tissue + Immunocytes remove cellular debris and pathogens internal to clot 3. Angiogenesis and granulation: + Blood vessels regrow into the wound (now called granulation tissue) + Fibroblasts in granulation tissue proliferate producing growth factors and new collagen + Macrophages remove old tissue and clot material 4. Epithelial regeneration and fibrosis: + Surface epithelium grows and migrates under the scab + Granulation tissue matures and contracts Lecture 8: Skeleton + Osseous Tissue Skeleton: - Organ system consisting of the bones - Also includes cartilage, ligaments, and other connective tissues Bones: - Primary organs of skeletal system - Primary function: Form framework of body - Made of osseous tissue and bone marrow - Interior cavity of bone contains connective tissue (has either red or yellow bone marrow) - Two types: + Compact: Dense or cortical, makes up 80% of total mass, white, smooth, solid + Spongy: Internal to compact bone, appears porous, makes up 20% of total bone mass Cartilage & Other CT: - Cartilage is semi-rigid connective tissue, more flexible than bone. Of three types, 2 are found in skeleton: + Hyaline Cartilage: Connects ribs to sternum (costal) Covers the ends of most bones at the moveable joints (articular) Supports external nose (nasal) Found within growth plates (epiphyseal) Provides model for bone formation during development + Fibrocartilage: Located at sites of heavy pressure and stretching, such as intervertebral discs, menisci in knee joints, and pubic symphysis - Other CT: + Ligaments: Dense regular CT anchoring bones to each other + Tendons: Dense regular CT anchoring muscle to bone Bone Function: - Support and Protection: + Serve as framework for the body + Protects tissues and organs from trauma - Movement: + Attachment site for muscles as well as other soft tissue + Act as a system of levers to modulate direction and magnitude of force - Hematopoiesis: + Process of blood cell production + Occurs in red bone marrow - Storage of mineral and energy reserves: + Storage site of Ca2+ (important signalling molecule) and PO42- (important for ATP) + Lipids stored in yellow bone marrow Bone Classifications: - Flat Bones: + Flat, thin surfaces + May be slightly curved + Protect underlying soft tissue and serve as large surface area for muscle attachments + Ex: Cranial vault of skull, scapulae, sternum and ribs - Long Bones: + Longer than they are wide + Have elongated cylindrical shaft (diaphysis) and two ends (epiphysis) + Most common bone shape + Found in upper and lower limbs except wrists and ankles - Short Bones: + Approximately same length as width + Ex: Wrist and ankle (carpal and tarsal) and sesamoid bones - Sesamoid Bones: + Found within tendons + Small, flat, oval-shaped + Increase muscle leverage + Ex: Patella - Irregular Bones: + Elaborate, complex shapes, like hip bones and vertebrae Long Bone: - Diaphysis + Long, hollow, cylindrical shaft + Provides leverage and weight support + An external, relatively thick layer of compact bone and an internal thin layer of spongy bone and an internal thin layer of spongy bone surrounds central medullary cavity - In children, medullary cavity has red marrow - In adults, medullary cavity has yellow marrow - Epiphysis + Knobby ends of long bone + External thin layer of compact bone and internal core filled with spongy bone (resists stress in all directions) + Located at moveable joints, covered in articular cartilage to reduce friction and absorb shock - Metaphysis + Region of mature bone between diaphysis and epiphysis + Contains growth plate (epiphyseal plate) Macroscopic Features: - Periosteum: + Covers external surface of bone, consisting of two layers: + Outer fibrous layer: Dense irregular CT Protects bone from surrounding structures Anchors blood vessels and nerves Attachment site for tendons and ligaments + Inner cellular layer: Osteoprogenitor cells, osteoblasts, and osteoclasts + Secured to underlying bone by perforating fibers - Endosteum: + Covers internal surface of bone within medullary cavity + Incomplete layer of cells containing osteoprogenitor cells, osteoblasts and osteoclasts Other Bone Structures: - Short, flat, and irregular bones differ from long bones - External surface is compact, interior is spongy bone (in skull, called diploe) - No medullary cavity Marrow: - Marrow is soft connective tissue of bone - Red: + Hematopoietic tissue + In adults, located within spongy section of long bones and diploe of flat bones - Yellow: + Replaces red marrow in medullary cavities of adults + Primarily adipocytes + Extreme anemic conditions can convert yellow marrow back to red marrow Type of Bone Cells: - Osteoclasts (Reabsorbs bone): + Multinuclear phagocytic cells + Derived from hematopoietic progenitor + Located within depressions on bone surface called resorption lacuna + Breaks down bone matrix during resorption - Osteocytes (Maintain bone tissue): + Mature bone cell residing within lacunae in bone matrix + Cannot make new bone + Connected to other osteocytes + Maintain bone matrix and detect mechanical stress in matrix - Osteoblasts (Form bone matrix): + Produce new bone matrix (osteoid) + Become trapped within calcified osteoid + Differentiate into osteocytes - Osteogenic cells (Stem cells): + Osteoprogenitor cells + Mitotic stem cells found in periosteum and endosteum + Can give rise to osteoblasts Composition of Bone Matrix: - Organic: + Osteoid (roughly 1/3rd of matrix), has collagen fibers and semi-solid ground substance made of proteoglycans and glycoproteins + Cells + Gives bones tensile strength + Resists stretching and twisting - Inorganic: + Mineral salts (roughly 2/3rd of matrix), primarily Ca3PO42, which combined with other salts to perform hydroxyapatite crystals which deposit along long axis of collagen + Hardens the matrix + Accounts for rigidity and inflexibility + Gives bone compression strength Bone Matrix Formation & Resorption: - Formation: + Osteoblasts secrete bone matrix, osteoid + Osteoid calcifies + Occurs as a result of high-plasma Ca2+ levels or when bone needs to respond to greater stress - Resorption: + Osteoclasts destroy bone matrix + Releases Ca2+ into blood plasma Osteon: - Structural unit of compact bone, weight-bearing pillars - Runs parallel with long axis - Resists torsion (twisting) stress, has bulls-eye appearance when viewed in cross-section Components: - Central Canals: + Contains small blood vessels and nerve fibers that serve osteon’s cells. Runs parallel to long axis of bone - Composed of Concentric Lamella: + Collagen fibers running in alternating directions in each lamella, gives bone strength and substance - Osteocytes:  + Mature bone cells isolated in lacunae that maintain the bone matrix - Lacunae: + Contain osteocytes, found at junctions of lamellae - Canaliculi: + Tiny canals between canaliculi. Osteocytes connected by gap junctions to communicate with one another and pass nutrients Compact Bone Structures: - Perforating (Volkmann) canals: + Connect and supply small blood vessels and nerves to the central canals and medullary cavity + Found at right angles to the long axis of bones - Circumferential lamellae: + Rings of bone that run the entire circumference of bone + Protect against torsion + External circumference lamellae found internal to periosteum + Internal circumference lamellae found internal to endosteum - Interstitial lamellae: + Located between intact osteon + Incomplete and have no central canal + Remnants of resorbed osteons or fill-ins Spongy Bone Structures: - Structure appears more haphazard - Open Lattice - Trabeculae: + Narrow plates and rods of bone + Align along lines of stress + Distribute stress throughout - No osteons: + Possess parallel lamellae + No blood vessels + Some canaliculi open to surface to allow diffusion of nutrients and waste Hyaline Cartilage: - Resilient and flexible  - Covered by dense irregular connective tissue called perichondrium - Avascular, lacks nerves - Nutrients supplied to cells by diffusion - Extracellular matrix: + Primarily collagen + Ground substance similar to bones but lacks inorganic salts + Contains 60-70% H2O + Highly compressible and good shock absorber - Cells: + Chondroblasts: Produce matrix, from mesenchyme + Chondrocytes: Mature cartilage cell found in lacunae, maintains matrix Cartilaginous Growth (Length): - Begins during embryonic development - Gives rise to bone growth - Both types occur simultaneously - Interstitial growth has four steps and occurs within internal regions of cartilage 1. Chondrocytes in lacunae undergo mitotic division 2. Daughter cells are chondroblasts 3. As chondroblasts secrete matrix, they are forced to separate. Become chondrocytes once they enter individual lacuna 4. Cartilage grows as chondrocytes produce more matrix - Interstitial Growth declines as cartilage becomes semi-rigid - 5 zones of growth: 1. Resting Cartilage: + Most distal from medullary cavity of diaphysis + Resembles healthy cartilage + Secures epiphysis to epiphyseal plate 2. Proliferating Cartilage + Rapid mitotic division + Cells aligned in columns 3. Hypertrophic Cartilage + No longer dividing + Cells become hypertrophic and reabsorb matrix 4. Calcified Cartilage + Mineral deposition in the matrix + Chondrocytes die 5. Ossification  + Vascularization and bone deposition Cartilaginous Growth (Width): - Begins during embryonic development - Gives rise to bone growth - Both types occur simultaneously - Appositional growth occurs along cartilage outer edge and has three steps: 1. Undifferentiated stem cells in perichondrium divide 2. Committed cells differentiate into chondroblasts located at the periphery of old cartilage and produce matric 3. Chondroblasts are pushed apart by new matrix and become chondrocytes - cartilage grows at periphery - Once cartilage becomes semi-rigid, further growth is at periphery - Cartilage growth stops when cartilage becomes mature Bone Formation: - Ossification or osteogenesis - Begins in embryo through childhood and adolescence - Two types, result in different kind of bone formations + Intramembranous yields flat bones + Endochondral yields most skeletal bones (Long bones, bones of pelvis, vertebrae, clavicle) Intramembranous Ossification: - Bone growth within membrane - Fibrous connective tissue is used as a supportive structure on which ossification occurs - Formation of flat bones - 4 Steps: 1. Formation of Ossification Centre + Committed osteogenic cells divide to become osteoblasts by secreting osteoid + Several ossification centers can occur simultaneously 2. Calcification of Osteoid 3. Formation of woven bone and periosteum + Woven bone is immature and unorganized + Mesenchyme condenses and forms periosteum  + Blood vessels form and branch 4. Replacement of woven bone by lamellar bone Endochondral Ossification: - Bone development that replaces cartilage and is used as a model for construction - 6 Steps: 1. Fetal hyaline cartilage model develops (week 8-12) 2. Cartilage calcification and formation of the periosteal collar 3. Primary ossification center forms in the diaphysis 4. Secondary ossification center forms in the epiphysis 5. Bone replaces almost all cartilage. Articular cartilage remains on epiphyseal plate, the junction between diaphysis and epiphysis 6. Lengthwise growth continues until epiphyseal plate closes (ossifies between ages 10-25) Interstitial Bone Growth: - Lengthwise growth - Dependent upon cartilage growth within epiphyseal plate Growth on epiphysis side of plate, chondrocytes calcify because deprived of nutrients, remodeling of calcified cartilage by bone tissue on diaphysis side of plate - Epiphyseal plate closes after adolescence Chondroblasts in epiphyseal plate divide less frequently and eventually replaced by bony tissue Epiphysis and diaphysis fuse Appositional Bone Growth: - Width growth - Bone added to external surface - Bone resorbed on the internal surface - Rate of addition > rate of resorption (leads to thicker, stronger bones) Bone Mass is Recycled: - Bone continues to renew and reshape Recycle 5-7% of bone mass every week Occurs ar periosteal and endosteal surfaces of bone Compact bone replaces slower than spongy bone  - Two processes Bone deposition Bone resorption - Regulated by 2 primary factors Hormones Mechanical stress (Wolff’s law - Bones grow or remodel in response to demands) Hormones: - Growth Hormone + Produced in anterior pituitary gland + Stimulates liver to produce somatomedins which stimulate chondrocyte activity - Thyroid Hormone + Produced in thyroid gland + Regulates metabolic rate of cells + Promotes activities of other hormones - Sex Hormone + Produced in the gonads and the adrenal glands + Includes estrogen and androgens + Secreted in large amounts at puberty - Glucocorticoids + Produced in adrenal gland + Regulate blood glucose levels + High levels interfere with growth at the epiphyseal plate - Serotonin + Usually a neurotransmitter in the nervous system, but can behave like a hormone + Receptors on bone cells regulate rate of bone remodeling Calcitriol, PTH, Calcitonin: - Calcitriol: Vitamin D produced in skin on exposure to UV light from cholesterol precursor Converted into active form by two enzymatic reactions (one in liver and one in kidney) Increases intestinal reabsorption of Ca2+ and PO43- - Parathyroid hormone: Produced in parathyroid gland Secreted in response to low Ca2+ levels  Acts on bone (increase osteoclast activity), kidney (Ca2+ and PO43-, production of calcitriol), small intestine (more calcitriol increases absorption of Ca2+) - Calcitonin: Produced in C cells of thyroid gland Counteracts activity of pTH Secreted in response to high Ca2+ levels Acts on bone (inhibits osteoclast) and kidney (favors Ca2+ filtration) Fractures and Repair: - Break the bone - Several classifications - Repair: 1. Hematoma results from blood vessels in bone being torn 2. Formation of fibrocartilaginous callus - Fibrous tissue invades the site and begins depositing collagen to span the break - Osteoblasts begin to deposit spongy bone within fibrous matrix - Furthest from blood supply - matrix calcifies and serves as splint 3. Bony callus formation - New bone replaces cartilaginous tissue 4. Bone remodeling - Excessive material is removed - Final structure resembles previous bone Lecture 9: Skeletal Features Bone markings: - Surface features that characterize each bone in the body - Depressions: + Clefts located when bone meets another structure + Allow blood vessels and nerves to travel along the bone + Allows two bones to articulate + Types of Depressions: - Facet - Fossa - Fovea - Groove - Openings: + Holes in the bone + Indicate where blood vessels or nerves travel through bone + Types of Openings: - Canal (meatus) - Fissure - Foramen - Projections: + Varied bone extensions + Places where muscles, tendons, and ligaments attach to bone + Types of Projections: - Condyle - Crest - Head - Tubercule - Epicondyle - Process - Spine - Protuberance - Trochanter - Line Divisions of Skeleton: - Axial: + Forms long axis of body + Bones involved with protecting, supporting, and carrying other body parts + Includes: Skull, vertebral column, rib cage - Appendicular: + Bones of upper limbs, lower limbs, and girdles + Bones involved in locomotion + Includes hip and shoulder Skull: - Most complex bony structure - 22 Bones 8 Cranial 14 Facial - Most are flat bones - Bones are joined together by sutures - interlocking joints with serrated appearances Cranium: - Encloses the brain and furnishes attachment sites for head and neck muscles - Single bones: Frontal, occipital, ethmoid, sphenoid bone - Paired bones: Temporal and parietal bones - Two parts: - Cranial Vault: Round portion making up superior, lateral, and posterior portions of the skull - Cranial Base: Makes up floor and interior potion of skull Foramen magnum: Where spinal cord exits cranium Cranial Fossae: - Contoured depressions making up floor of cranium - Anterior cranial fossa: + Frontal bone, ethmoid bone and sphenoid bone + Supports frontal lobe - Middle cranial fossa:  + Sphenoid and temporal bone + Supports temporal lobe and pituitary gland - Posterior cranial fossa: + Temporal bone and occipital bone + Supports the cerebellum and part of the brainstem Cranial Sutures: - Immovable joints that form boundaries between cranial bones - Four Major Sutures: + Coronal Suture: - Extends laterally across superior surface along coronal plate - Articulation between frontal and parietal bones + Lambdoid Suture: - Arc across posterior surface of skull - Looks like (l) - Articulation between parietal and occipital bones + Sagittal Suture: - Extends between coronal and lambdoid sutures along sagittal plane - Articulates between paired parietal bones + Squamous Suture: - One on each side of skull - Articulates between temporal and parietal pain (on side) Facial Skeleton: - Bones that form framework for the face - Single bones: Mandible and Vomer - Paired bones: Nasal, lacrimal, zygomatic, palatine, maxilla, inferior nasal concha - Function Contain/form cavities for sight, smell, taste organs Turbinate air Provides openings for the passage of air and food Secure teeth Anchor facial muscle Skull Cavities: - Cranial Cavity: + Largest + Surrounds the brain - Orbital Cavity: + Contain eyeballs, blood vessels, muscles, nerves, and lacrimal glands to secrete tears + Formed by frontal, sphenoid, ethmoid, zygomatic, palatine, maxilla, and lacrimal bones - Nasal Cavity: + Contains passages for air and special sensory neurons for smell - first part of respiratory tract + Divided by septum (formed by vomer and ethmoid bone) + Formed by sphenoid, ethmoid, palatine, nasal bones, maxilla, and inferior nasal concha - Oral Cavity: + Teeth, tongue, passage for food and air, most of salivary glands + Formed by mandible and maxilla Nasal and Paranasal Sinuses: - Air-filled chambers within skull bones - Located around nasal cavity: Four paranasal sinuses named for bone they are located in - Possess small openings between sinuses and nasal cavity - Mucus-lined and air-filled: Air moves in from nasal cavity, mucus drains out to nasal cavity - Function: Helps to warm and humidify air, lighten skull, enhance voice resonation Hyoid Bone: - Found in anterior neck region - No direct articulation with any other bones Position maintained by a combination of ligaments and muscles - Two pairs of projections called lesser and greater horns Important sites of attachment for muscles involved in swallowing and speech production Vertebral Column: - Five divisions and four curvatures  + 7 Cervical vertebrae - Small and oval body shape, C1 lacks body, C2 has dens on superior surface - Triangular foramen shape - Certain transverse foramina - Spinous processes are mostly fork-shaped - C1 has no spinous process - Concave curvature + 12 Thoracic vertebrae - Larger and heart-shaped, contain costal facets - Circular foramen shape - Long transverse processes, contain articular facets for ribs called costal facet - Long spinous process, point inferiorly - Convex curvature + 5 Lumbar vertebrae - Largest body, kidney shaped - Flattened triangular foramen - Short transverse processes with no facets or foramina - Thick spinous processes point posteriorly - Concave curvature + 5 Sacral vertebrae - Vertebrae are fused into the sacrum - Superior articular process connects to hip - Possesses foramen for blood vessels and spinal nerves to pass through - Convex curvature + 4 Coccygeal vertebrae - Fused vertebrae called coccyx - Attachment site for several ligaments - Letter designates the type of vertebrae and a number its position - Spine curves to provide flexibility and increased resilience to support weight of body Structure of Vertebrae: - Body - Weight-bearing portion - Located anteriorly - Vertebral foramen - Space between the body and arch - Make up the vertebral canal - Vertebral arch - Composite structure  - Located posteriorly - Composed of two pedicles and two laminae - Spinal process: - Single, extends anteriorly - Articular processes: - Two pairs, extends superiorly and inferiorly - Transverse process - One pair, extend laterally Intervertebral discs: - Reside between vertebrae to provide cushioning - Two parts: + Anulus fibrosis: - Outer portion - Composed of collagen fibers and fibrocartilage - Limits expansion of nucleus pulposus + Nucleus pulposus: - Inner portion of disc - Elastic and compressible Thoracic Cage: + Sternum: - Breastbone - Stabilizes thoracic cage - Protects heart, vena cava, and thymus - 3 Bones: + Manubrium: Articulates with clavicle and ribs + Body: Articulates with ribs + Xiphoid Process: Initially hyaline cartilage - ossifies by age 40 Attachment point for abdominal muscles + Ribs: - All attach posteriorly to thoracic vertebrae  - Ribs 1-7 are true ribs because they attach directly to sternum - Ribs 8-12 are false ribs because 8-10 attach to Rib 7 while 11-12 are floating ribs Rib Structure: - Bowed flat bone - Shaft: + Comprises bulk of rib - Head: + Articulates with thoracic vertebrae at costal groove + Divided into superior and inferior articular facets - Neck: + Area between head and tubercle - Angle: + The point where the rib curves toward the sternum - Tubercle: + Articulates with transverse process of the vertebrae Pectoral Girdle: + Clavicle: - Collar bone - Anterior location - Attachment bone for many muscles - Acts as brace to hold arms and scapula away from body + Sternal end: Articulates with manubrium of sternum + Acromial end: Articulates with acromion of scapula + Scapula: - Shoulder blade - Posterior location: Attached to axial skeleton via articulation with clavicle and various muscles - Dorsal surface possesses ridge called the spine, ending with acromion that articulates with clavicle - Lateral border: Glenoid cavity articulates with humerus - Three fossae for muscle attachment: + Ventral surface: Subscapular + Dorsal surface: Supraspinous and Infraspinous Humerus: - Articulates with scapula to form shoulder + Head: Proximal end - Fits into glenoid cavity + Tubercules: Attachment sites for rotator cuff + Deltoid tuberosity: Attachment for deltoid muscle - Articulates with ulna and radius to form elbow, distal end: + Capitulum: Lateral, articulates with head of radius + Trochlea: Medial, articulates with trochlear notch of ulna + Epicondyles (lateral and medial): Attachment site for muscles, ulnar nerve posterior to medial epicondyle Forearm: - Includes Ulna and Radius, connected via interosseous membranes + Ulna: - Medial bone - Longer than radius - Trochlear notch forms elbow joint with humerus - Olacrannon is bone end of elbow - Styloid process connects to wrist + Radius: - Lateral bone - Styloid process connects to wrist Carpal Bones: - Wrist bones - Eight per wrist, united by ligaments - Two rows, lateral to medial Proximal: Scaphoid, Lunate, Triquetrum, Pisiform Distal: Trapezium, Trapezoid, Capitate, Hamate Hands: - Palms: + Five metacarpal bones (Thumb/pollux (I) to Pinky (V))  + Heads of metacarpals make up knuckles - Fingers: + 14 phalanges + Thumb has two phalanges, index finger-pinky have 3 phalanges Pelvic Girdle: - Attaches lower limbs to axial skeleton - Refers to pair of os coxae (hip bones) - starts out as three pairs, but fuse together - Three bones: + Ilium: (Superior) Iliac crest - protrudes, regarded as hip Serves as attachment point for muscles of trunk, hip and thigh Articulates with sacrum at the sacroiliac joint + Ischium: (Inferior) Bear weight of the body when sitting via paired ischial tuberosities + Pubis: (Posterior) Joined by pubic symphysis - fibrocartilage disc - Obturator foramen: - Articulates with femur at acetabulum (fusion point of all three bones) - Female pelvis is wider and shallower Thigh - Femur: - Femur: Largest and strongest bone in the body (¼ size of height), covered with bulky muscles, head articulates with hip + Trochanters: Greater projects laterally, lesser projects posteromedially. Processors serve as insertion sites for gluteal and thigh muscles + Shaft: Moves medially, allows knees to be closer to body’s center of gravity. + Condyles: Lateral and medial articulate with tibia to form knee joint - Patella (Kneecap): Enclosed in quadriceps femoris tendon, protects knee joint, improves leverage of thigh muscle Lower Leg: + Tibia: - Larger of the two bones - Head articulates with femur  - Located medially - Bears weight of body and transfers it to foot - Articulates with fibula and talus to form ankle (medial malleolus: bony process forming inside of ankle bone) + Fibula: - Smaller of two bones - Head articulates with tibia - Located laterally - Articulates with tibia and talus to form ankle (Lateral malleolus: process forming outside ankle bone) Tarsal Bones: - Ankle bones - Seven bones located distal to lower leg: + Talus, Calcaneus + Navicular + Medial cuneiform, Intermediate cuneiform, Lateral cuneiform, Cuboid - Two bones of interest: + Talus (ankle): Articulates tibia and fibula + Calcaneus (heel): Attached to Achilles tendon The Foot: - Metatarsals: Five long bones located distal to tarsal bones and proximal to phalanges Enumerated medial to lateral I-V - Phalanges Hallus (Big toe) 2 phalanges Other toes have 3 Arches of foot: - Provide strength to foot - Allows for give in foot - Maintained by attachment between bones, ligaments, and tendons - Two longitudinal arches: + Medial Longitudinal Arch:  - Highest arch - Prevents medial side of foot from touching the ground - Gives footprint characteristic shape - Extends from ball of foot to heel + Lateral Longitudinal Arch: - Not as high - Contributes to footprint - Extends from little toe to heel + One transverse arch: - Runs perpendicular to longitudinal arch - Formed by distal row of tarsal bones Lecture 10: More Skeletal Features Joints: - AKA articulation - Classified by function (amount of movement possible) and structure (how bones are bound together). - Where bones meet: bone, cartilage, teeth Joint Classification: - Structure: + Fibrous: Joined by fibrous tissue (Ex. Sutures) + Cartilaginous: Joined by cartilage (Ex. Epiphyseal plate) + Synovial: Bones are separated by fluid-filled synovial cavities (Ex. Elbow) - Movement: + Synarthroses: Immovable joints (Ex. Sutures) + Amphiarthroses: Slightly movable joints (Ex. Vertebrae) + Diarthroses: Freely movable joints (Ex. Elbow) Joint Mobility: - Range of motion: Normal extent of mobility for specific joint movement Typically refers to movement possible at freely-movable synovial joints Measured in degrees with protractor - Degrees of freedom: Number of axes in which movement at a joint occurs Best described in context of synovial joints Factors Affecting Joint Stability: - Articular surface shape: + Allow joint movement + Freedom of movement opposes joint stability - Number and position of ligaments:  + Prevent undesired movement + More ligaments = greater strength - Muscle tone: + Most important for stability + Tone is how contracted muscle is in a relaxed state + Keeps tendons taut and bone in a stable position + More tone = more stability Fibrous Joints: - Gomphoses: + Peg-in-socket joints + Only found in teeth in jaw + Synarthrosis (Immovable) - Sutures: + Lie between bones of skull + Interlocking irregular edges + Synarthrosis (Immovable) - Syndesmoses: + Bones connected by ligaments + Give allowed dependent on length of ligaments + Ex: Ulna + radius, tibia + fibula + Amphiarthrosis (Slightly movable) Cartilaginous Joints: - Synchondroses: + Articulation of bone with hyaline cartilage + Synarthroses - immobile + Ex: Epiphyseal plate and costal cartilage - Symphyses: + Pad of fibrocartilage between articulating joints + Amphiarthroses - slight mobility + Ex: Pubic symphysis, intervertebral discs Synovial Joints: - Articular capsule enclosing joint cavity that strengthens joint  Outer layer is fibrous capsule, inner layer is synovial membrane - Joint cavity filled with synovial fluid - secreted by synovial membrane, provides weight-bearing lubricant to joint - Possesses articular cartilage and protects bone ends - Reinforces ligaments Reinforce and strengthen joint Extrinsic - outside, separate from joint Intrinsic - inside, part of joint capsule - Diarthroses - Movable Bursae & Tendon Sheath: - Not part of joint - closely associated - Bursae: + Sac-like structure containing synovial fluid + Alleviate friction where bone, muscle, tendons and ligaments meet - Tendon sheaths: + Elongated bursae wrapped around tendon Classification of Synovial Joints: - Dependent on articulating surfaces and type of movement allowed - Movement described as relative to particular plane (axis) + Uniaxial - movement in one plane + Biaxial - movement in two planes + Multiaxial - movement in multiple planes - Plane Joint: + Least mobile, non-axial + Flat articular surface allows for short, gliding movements - Hinge Joint: + Cylindrical projection fits into trough-shaped bone - similar to door hinge + Flexion and extension + Uniaxial - Pivot Joint: + Round end of long bone protrudes into ‘sleeve’ of bone or ligament + Rotates longitudinal, uniaxial - Condyloid Joint: + Oval- shaped articular surface fits into complementary depression  + Permits all angular motions back-forth side-side - Saddle Joint: + Possess concave and convex surface on both bones + More range of motion than Condyle joint - Ball-and-Socket Joint: + Most mobile - triaxial + Spherical head of bone fits into cup-like socket on other bone + Freedom of movement Types of Movement: - Gliding: + One bone surface slips over another without appreciable angulation or rotation + Simple movement where two opposing surfaces slide against one another (front-back, side-side) + Limited movement and angel does not change + Occurs at plane, intercarpal, and intertarsal joints - Angular: + Increase or decreases angle between two bones + Flexion: Anterior-posterior plane, decreases angle between bones + Extension: Anterior-posterior plane, increases angle between bones + Hyperextension: Joints go past 180 degrees. + Lateral flexion: Lateral movement in coronal plane + Abduction: Lateral movement of body away from midline + Adduction: Lateral movement of body toward midline + Circumduction: Movement of limb creating cone in space - Rotation: + Turns bone around long axis + Pivoting motion. Lateral - external and Medial - internal + Pronation: Medial rotation of forearm - radius twists inward, ulna twists to face out + Supination: Lateral rotation of forearm - radius is outward, ulna is medial - Special: + Only occurs at specific joints + Limited to ankle joint: Dorsiflexion - Toes move toward leg and Plantarflexion - Toes dip below heel + At intertarsal joints: Eversion - Sole of foot faces outwards and Inversion - Sole of foot faces inwards + Protraction: Anterior non-angular movement in transverse region + Retraction: Posterior non-angular movement in transverse region  + Depression:Inferior movement of a body part + Elevation: Superior movement of a body part + Opposition: Movement of thumb to palmar tips allowing hand to grasp objects Skeletal Muscles as Levers: - Lever is a straight, stiff object that moves along a fixed pivot point (fulcrum) - Moment arm is distance from fulcrum to force - Applied force is applied to lever, resistive force acts against applied force - Mechanical advantage when load is near fulcrum and effort is applied far from fulcrum - Arrangement of skeletal muscles and bones as levers decrease force required to move bones - Bones are levers, joints are fulcrums, muscles apply force Lever Types: - First class: + Muscle force (effort) and resistive force act on opposite sides of fulcrum (joint) + Disadvantage: Large force necessary to work against small external resistance + Few 1st-class levers in body - Second class: + Muscle force (effort) and resistive force on same side of fulcrum + Muscle force moment arm longer than resistive force moment arm + Advantage: Muscle force necessary is less than resistive force + Few 2nd-class levers in body - Third class: + Muscle and resistive force on same side of fulcrum + Muscle force moment arm shorter than resistive force moment arm + Most common lever Temporomandibular Joint: - Articulation between mandible (condyle) and temporal bone (fossa) - Loose articular capsule supported by ligaments allows for variety of motion - Hinge-like action during depression when mandible sits in mandibular fossa - Mouth opens - mandible is protracted and braced against articular tubercle - GLiding motion allows for lateral movement during chewing Glenohumeral (Shoulder) Joint: - Ball and socket joint (Shallow glenoid cavity fits large head of humerus) - Glenoid labrum compensate for shallow fossa - Stability sacrificed for free movement - few reinforcing ligaments, primarily on anterior aspect Coracoacromial ligament, coracohumeral ligament, glenohumeral ligament - Muscle tendons crossing joint are primary stabilizers - Several bursae reduce friction Elbow Joint: - Three joints: + Humeroulnar hinge joint: True elbow joint. Trochlea of humerus articulates with trochlear joint of ulna. Allows flexion and extension + Humeroradial joint: Capitulum of humerus articulates with head of radius + Radioulnar pivot joint: Not functionally part of elbow. Allows pronation and supination of forearm - Side to side movements restricted by radial and ulnar collateral ligaments - Anular ligament surrounds neck of radius and binds it to ulna Hip Joint: - Ball-and-socket joint - Muscles and tendons from hip and thigh reinforce stability - Large range of motion still limited compared to pectoral girdle - Deep socket formed by acetabulum. Acetabular labrum: fibrocartilage deepens socket - Ligaments reinforce articular capsule + Iliofemoral (Anterior) + Ischiofemoral (Posterior) + Pubofemoral (Inferior) Knee Joint: - Primarily hinge joint: Bicondylar structure. Slight rotation and later gliding possible during flexion - Three joints: + 2 Tibiofemoral joints: Lateral and medial condyles of femur articulate with those of tibia  + Patellafemoral joint: Patella articulates with patellar surface of femur - Menisci - Incomplete articular capsule only includes medial, lateral, and posterior joint aspects. Anterior aspect covered by quadriceps tendons - Heavily reinforced by muscle tendon - Movement restricted in joints by ligaments and tendons - Collateral ligaments: + Taut on extension to reinforce lateral and medial surfaces + Fibular: Lateral support, protect against hyperadduction at knee + Tibial: Medial support, prevents leg from moving too far laterally relative to thigh - Cruciate ligaments: + Deep to articular capsule + Cross over one another + Anterior ACL - prevents hyperextension during extension + Posterior PCL - prevents hyperflexion during flexion - Patellar ligament: Connects patella to tibia Lecture 11: Skeletal Muscle Skeletal Muscle Function: - Produce movement (Physical movement - locomotion) - Protection and support (Hold intestinal organs in place and protect them) - Maintain posture and stabilize joints - Generate heat (When muscles work, some energy needed is converted into heat energy) - Interpersonal communication (Speaking, facial expressions, gestures, typing, writing) Muscle Characteristics: - Each skeletal muscle is a discrete organ - over 600 named muscles - Contractility: Forcibly shorten when stimulated - Excitability: Ability to receive and respond to a stimulus (chemical) - Extensibility: Stretch beyond resting length - Elasticity: Recoil and resume resting length - Plasticity: Constantly adapt based on usage Connective Tissue Components: - Support and reinforce whole muscle as a unit - Three concentric layers: + Epimysium: Surrounds whole muscle + Perimysium: Surrounds bundles of muscle fibers called fascicles + Endomysium: Surrounds the individual muscle fiber - Tendon: + Thick, cordlike structure of dense regular CT + Attaches muscle to bone, skin, or muscle + Formed by convergence of three concentric layers + Extend beyond muscle fibers + Attached to periosteum Microanatomy of skeletal muscle: - Sarcolemma: Plasma membrane of muscle fiber - Sarcoplasm: Cytoplasm of muscle cell + Contains several glycogen granules called glycosomes + Myoglobin stores O2 + High concentration of mitochondria + Multinucleated - Triad: + Transverse tubules: Membranous tubes traveling perpendicular to length of fiber Allow for conduction of action potential from surface of cell through t-tubules + Sarcoplasmic reticulum Modified ER, surrounds each myofibril like a mesh sleeve Storage for high calcium that facilitates muscle contraction when released + Terminal cisternae Blind-ended sacs at the end of SR adjacent to T-tubules Reservoir for calcium - Myofibril + Highly organized cytoskeleton + 100s–1000s in a single cell + Extends entire length of cell + Composed of myofilaments - Myofilament + Thick filament - Myosin > Composed of myosin: protein with 2 identical units of intertwined long tails and 2 globular heads > Two halves: Myosin oriented in opposing directions with heads facing outwards > Heads are responsible for cross-bridges and have actin-binding site and ATPase site + Thin filament - Actin > F-actin: Two strands of G-actin forming a helix, functional binding sites for myosin > Tropomyosin: Long chain binding to actin that hides myosin binding sites > Troponin: Bridges tropomyosin and actin and binds calcium Sarcomere: - Functional unit of muscle - Area between Z-lines (cytoskeletal disc that interconnects actin filaments)  - Muscles grow lengthwise by adding more sarcomeres Regions of sarcomere: - I band: Portion of thin filaments that project from Z lines and do not project into A band - A band: Region of thick filaments and overlapping thin filament - H zone: Slightly lighter than A band, where it lies - only consists of thick filaments - M line: Transverse proteins interconnecting thick filaments, extends down middle of A band and center of H zone Structural Proteins: - Nebulin: Inelastic protein that helps align actin filaments, attached to Z discs - Titin: Single-stranded elastic protein that extends along the length of thick filament from M line to Z line, acts as spring to passively recoil muscle cell to resting length after stretching, stabilize position of thick filament relative to thin filament - Dystrophin: Protein complex anchoring myofibrils to sarcolemma - Alpha actinin: Crosslinks antiparallel thin filaments Motor Unit: - Single alpha motor neuron and muscle fibers it innervates - Number of fibers in a motor unit varies: + Dependent on type of action formed - Delicate have few, Coarse have multiple - Fibers in motor unit are dispersed throughout a muscle - motor unit stimulation results in evenly distributed contraction Neuromuscular Junction: - Each skeletal muscle has one - Point where innervating neuron interacts with fiber - Synaptic knob: + Terminal end of motor neuron’s axon + Houses synaptic vesicles containing acetylcholine - Motor end plate: + Specialized region of sarcolemma underlying synaptic knob + Acetylcholine receptors: Chemically gated ion channels - Synaptic cleft: + Space between synaptic knob and motor end plate + Contains acetylcholinesterase which breaks down acetylcholine Muscle twitch: - Single contraction in a muscle fiber + Latent period: Time delay between stimulation and beginning of contraction + Contraction time: Onset of contraction to peak of tension + Relaxation: Roughly equivalent to contraction time - from peak of tension to rest - Stimulation of a muscle fiber produces a twitch which is too weak individually, but if they occur additively, causes muscle contraction Steps of Muscle Contraction: 1. Initiation: + Action potential arrives at synaptic knob - calcium enters synaptic knob and acetylcholine is released from synaptic knob + Acetylcholine binds receptor on muscle cell - sodium rushes into cell leading to end-plate potential, action potential is initiated and propagated, action potential travels length of cell and down T-tubules + Triggers open DHP channels + Causes opening of RyR channels - located on sarcoplasmic reticulum, allows for calcium to flow into cytoplasm 2. Crossbridge formation: + Calcium is released from sarcoplasmic reticulum + Calcium binds troponin on thin filament, causing tropomyosin to be pulled away from myosin allowing myosin and actin to bind together 3. Powerstroke + Myosin has ATP binding site, uses ATP to cock myosin head for interaction + If binding site is available, myosin binds actin and leads to powerstroke, releasing ADP and P + New ATP binds ATPase site, causes myosin to replace from actin 4. Contraction: - Length of bands shrink - Sliding filament mechanism - Thin filaments slide inward over stationary thick filaments towards center of A band. As thin filaments move, they pull Z lines closer - causing sarcomeres to shorten - H zones and I band shorten, A band remains the same 5. Relaxation - Acetylcholinesterase removes acetylcholine, ensuring no EPP (No EPP, no action potential)  - Sarcoplasmic reticulum has a calcium-ATPase pump (SERCA) which actively pumps calcium from cytosol into SR - For no action potential: No calcium released, calcium pumped out of cytosol. Actin and myosin cannot interact ATP Essential for Muscle Metabolism: - Limited stores of ATP in muscles, so muscles must use different pathways to supply additional ATP during contractions depending on need - Immediate supplies via phosphagen system + Does not require oxygen, immediate formation of ATP, burns early quickly + Small amounts of stored ATP: ATP hydrolyzed by ATPase to release about 5-6 seconds worth of energy + Myokinase transfers phosphate from one ADP to another to make ATP - 2 secs worth of energy + Creatine phosphate stores phosphate. Creatine kinase transfers phosphate between Creatine phosphate and ADP to make ATP - 10-15 seconds worth of energy - Short-term supplies via anaerobic respiration + Some glucose stored in muscle as glycogen + Pyruvate from glycolysis converted into lactic acid instead of entering TCA. + Occurs rapidly, last resort - Long-term supplies via aerobic cellular respiration + Requires oxygen + Relatively slow and dependent on nutrients being delivered to muscle + High ATP yield + Myoglobin increases rate of O2 transfer from blood to muscle Lecture 12: Muscle Fiber Muscle Fiber Types: - Twitch time: + TYPE 1: Slow twitch. Long time to develop force and relax + TYPE 2a&b: Fast twitch. Rapidly develop force and relax - Power development + TYPE 1: Limited in ability to produce force rapidly + TYPE 2a&b: Produce force very rapidly - Fatigue-resistance: (Dependent on ATP production) + TYPE 1: Generally efficient and resistant to fatigue. Have high capacity for aerobic energy supply - Oxidative relies on oxidative phosphorylation, yields more ATP, fatigues slower than glycolysis + TYPE 2a&b: Inefficient and highly fatiguing. Low aerobic capacity - Glycolysis for ATP, glycolytic fibers are fatigable - TYPE 1: Red muscle + Slow, less powerful contractions + Smallest muscle cell + Large amount of myoglobin - TYPE 2a: Red muscle + Least numerous + Intermediate size - TYPE 2b: White muscle + Most prevalent + Fast and most powerful contraction + Largest in diameter + Significantly less myoglobin Twitches and Tetanus: - Wave summation: Temporal summation of twitches  - Incomplete tetanus: Quivering contraction from summed contractions, but stimulation occurs far enough apart that incomplete rest occurs - Tetanus: Smooth, sustained contraction at maximal strength resulting from rapid successive action potential Motor Unit Recruitment: - Force of contraction accomplished by recruitment + Threshold stimulus: Stimulus where first observable contractions occur + Maximal stimulus: Strongest stimulus where all motor units are recruited - Muscle fiber summation + Addition of motor neuron pools to increase tension + Ensures constant force over time - Fibers in motor unit disperse throughout muscle + A stimulation of motor unit will result in evenly distributed contraction (twitch) - Fatigue is inability to maintain muscle tension + Countered by asynchronous recruitment of motor units + Recruitment of fatigue-resistant muscles first and quickly-fatiguing muscles last Primary Types of Contraction: - Isotonic: Muscle tension (force generated) remains constant as muscle length changes + Concentric: Muscle shortening with tension + Eccentric: Muscle lengthens with tension - Isometric: Muscle doesn’t change length, so tension develops at constant muscle length Muscular Adaptation: Hypertrophy: - Enlargement of muscle fiber cross-sectional area following training + Involves synthesis of contractile proteins actin and myosin within myofibril + Increase in the number of myofibrils in the muscle fiber - Beneficial for power and force production - Type 2 fibers have greater potential for hypertrophy + Lead to increase force generation - Generally detrimental to aerobic performance + Fewer capillaries + Muscles fatigue more easily Altering Characteristics of Muscle Fibers: - Proportions of muscle fibers are genetically determined - Training can lead to changes within subtypes + High intensity resistance training and aerobic endurance training, type 2b fibers can become more oxidative to type 2a fibers + Type 1 to Type 2 transitions appear less probable - Cannot change muscle type - only improve muscle fitness Adaptations Due to Resistance and Sprint Training: - Leads to increased cytoplasmic, sarcoplasmic reticulum, and t-tubule density: + Accommodates muscle hypertrophy, enhances muscle function, and enables greater expression of strength - Enhanced Calcium release assists in increasing speed and power production - Decrease blood and muscle pH during exercise: + Better tolerates accumulation of H+ in the working muscle, delays fatigue and produce greater muscular endurance Adaptations Due to Aerobic Endurance Training: - Increased aerobic capacity of the skeletal system + Allows performance at the same time absolute intensity with less effort - Increases maximal aerobic power - running the same distance faster with the same perceived effort - Increase size of Type 1 muscle fibers - not as large as that in Type 2 fibers - Increases in size and number of capillaries and mitochondria, enhancing cell ability to receive oxygen and muscle ability to utilize oxygen to produce ATP via oxidation and resist fatigue Effects of Inactivity: - Sedentary leisure activities lead to skeletal muscle mass and tone loss - Skeletal muscle that is not regularly stimulated atrophies + Reduction in muscle tone, size, and power + Initially reversible + Dying muscle fibers cannot be replaced Origins and Insertions: - Muscles are attached bone - Origin: Muscle’s Proximal Attachment: + Usually more stationary attachment + Usually attached via ‘fleshy’ attachments - epimesium attached to periosteum, distributes force - Insertion: Muscle Distal Attachment + Usually more mobile + Usually attached via ‘fibrous’ attachments - tendons, focuses force Movement and Force Generation: - All movement involves action of more than one muscle - Agonist: + Muscle or muscle group directly involved in creating a movement - Antagonist: + Opposing muscle or muscle group to agonist + Stabilizing a joint during movement + Slows down limb at end of fast movement + Antagonist muscle is relaxed while agonist muscle creates movement + Reciprocal inhibition: CNS signals contraction in agonist and relaxation in antagonist - Synergist: + Stabilize body during movement, but not directly responsible for bringing about movement Muscle Fiber Alignment: - Pennate muscles: + Muscle fibers attach obliquely to tendon + High angle of pennation means there is little muscle force being transmitted to tendon + Produce greater force due to greater density of cross bridges/muscle volume - Non-pennate muscles: + Muscle fibers are parallel to the line between the origin and insertion + Muscles produce higher velocities due to greater number of sarcomeres in a row Muscle Names: - Human body has over 500 skeletal muscles - Names to muscles provide clues to location, position, structure, size, shape, origin and insertion, action  - Orientation of muscle fibers - rectus - Size - Brevis, longus, major, minor, vastus - Shape of muscle - Deltoid, rhombus, quadratus - Named for action - Abductor, adductor, depressor Smooth Muscle: - Spindle-shaped, uninucleate, smaller than skeletal muscles - No sarcomeres - dense bodies containing same protein as Z-lines held in place intermediate filaments - Create more cross-bridges than skeletal muscles because greater ratio of myosin to actin - Myosin and actin create diamond shaped lattice + Fewer thick and thin filaments than skeletal muscle + Thick myosin filaments longer than in skeletal muscle + Thin actin filaments have no troponin + Intermediate filaments - part of cytoskeleton, non-contractile - Connected by mechanical junctions - sometimes electrically coupled gap junctions - Well-defined sarcoplasmic reticulum sequesters Ca2+ next to caveolae (invaginations of cell membrane) - NO t-tubules - Found in walls of hollow organs + Typically arranged in two sheets (syncytium) + One runs parallel to long axis of organ + One runs circumferentially + Branch together in bundles as opposed to skeletal fibers running parallel to each other - Responsible for involuntary movements + Blood flow + Movement along digestive and urinary passageway + Change resistance to airflow in respiratory passages + Contraction/relaxation of uterus Smooth Muscle Contraction + Relaxation: - Contraction: 1. Stimuli triggers opening of voltage-gated calcium channels 2. Binding of calcium to calmodulin 3. Activation of myosin light-chain kinase by calcium-calmodulin complex 4. Activated MLCK phosphorylates myosin head  5. Cross-bridge formation formed by myosin head binding to thin filaments. Myosin ATPase hydrolyzes ATP to provide energy for powerstroke. Process repeats to generate force for muscle contraction - Relaxation 1. Remove calcium 2. Dephosphorylate myosin light chain with myosin phosphatase - Contraction features: + Stress-relaxation response: Allows hollow organ to fill or expand slowly to accommodate a greater volume without promoting strong contraction + Capable of functioning efficiently even when twice or half its resting length + Hyperplastic: Certain smooth muscle fibers divide to increase their numbers (like uterus) + Terminal branches of autonomic nervous system travel along multiple smooth muscle cells releasing neurotransmitters from bulbs (varicosities) that diffuse to cells underlying terminal + Innervation does not always initiate contraction but can modify rate and strength of contraction Smooth muscle contraction: - Multiunit smooth muscle: + Made up of discrete motor units that function independently + Have neuromuscular junction + Ex: Large blood vessel muscles, hair follicles, lens and iris of eye, small airways of lungs - Single-unit smooth muscle: + Electrically connected by gap junctions + Contract as a single coordinated unit + Self-excitable: Resting potential fluctuates without influence from external forces resulting in spontaneous depolarization - Only a small portion of cells are self-excitable - Once initiated, impulse is conducted throughout remaining non-self-excitable cells