Anatomy_ Concepts Flashcards
What are the steps taken to prepare tissue for microscopic viewing?
specimen must be fixed (preserved) and then cut into sections (slices) thin enough to transmit light or electrons then stained to enhance contrast
Each cell can:
Obtain nutrients and other essential substances from the surrounding body fluids.<br></br>Use these nutrients to make the molecules it needs to survive.<br></br>Dispose of its wastes.<br></br>Maintain its shape and integrity.<br></br>Replicate itself.
Human cells have three main parts:
the plasma membrane, the cytoplasm, and the nucleous
plasma membrane proteins are of two distint types:
integral proteins and peripheral proteins
The functions of a plasma membrane:
“1. The plasma membrane provides a protective barrier against substances and forces outside the cell<br></br>2. Some of the membrane proteins act as receptors; that is, they have the ability to bind to specific molecules arriving from outside the cell. After binding to the receptor, the molecule can induce a change in the cellular activity. Membrane receptors act as part of the body’s cellular communication system.<br></br>3. The plasma membrane controls which substances can enter and leave the cell. The membrane is a selectively permeable barrier that allow some substances to pass between the intracellular and extracellular fluids while preventing others from doing so.”
Three types of endocytosis
phagocytosis, pinocytosis, and receptor-mediated endocytosis
Describe endocytosis
for large particles and marcomolecules; the substance is enclosed by an infolding part of the plama membrane. In the region of invagination, specific proteins may cover the inner surface of the plasma membrane. This protein coat aids in the selection of the substance to be transported and deforms the membrane to form a membrane-walled sac called a vesicle. The membranous vesicle is pinched off from the plasma membrane and moves into the cytoplasm, where its contents are digested.
peroxisome enzymes:
oxidases and catalases and others: oxidases use oxygen to neutralize free radicals, converting these to hydrogen peroxide; hydrogen peroxide is converted into water and oxygen by catalase, to break down poisons that have entered the cell
cytoskeleton has three types of rods:
microfilaments, intermediate filaments, and microtubles
How do most organelles move within the cytoplasm?
pulled along the microtubles by small motor proteins, kenesins and dyneins
How do cells differentiate and take on specialized structures and functions?
Cells in each region of the developing embryo are exposed to different chemical signals that channel the cells into specific pathways of development. The cytoplasm of a fertilized egg contains gradients of maternally produced mRNA molecules and proteins. In the early days of development as the fertilized egg divides, the cytoplasm of each daughter cell receives a different composition of these molecules. These maternally derived molecules in the cytoplasm influence the activity of the embryonic genome. In this way, different genes are activated in each cell, leading to cellular differentiation.
What functional groups do cells fall into?
a) cells that connect body parts or cover and line organs (fibroblast, epithelial cells, erythrocyte)<br></br>b) cells that produce movement and move body parts (skeletal muscle and smooth muscle cells)<br></br>c) cell that stores nutrients (fat cell)<br></br>d) cell that fights disease (macrophage (a phagocytic cell))<br></br>e) cell that gathers information and controls body functions (nerve cell (neuron))<br></br>f) cell of reproduction (sperm)
life cycle of a cell
interphase (G1, S1, G2), prophase (early, late), metaphase, anaphase, telophase, cytokinesis. Mitosis consits of prophase, metaphase, anaphase, and telophase
how is DNA packed?
The double helix of DNA is packed with protein molecules and coiled in strands of increasing structural complexity and thickness. The DNA molecule plus the proteins form chromatin. Each two turns of the DNA helix is packed with eight disc-shaped protein molecules called histones. Each cluster of DNA and histones is called a nucleosome. Chromatin can be in the form of either extended chromatin (while being copied onto messenger RNA in a process called transcription), or further coiled into a tight helical fiber called condensed chromatin. During cell division, the chromatin is further packed, nucleosomes are looped and then packed further into the chromatid of a chromosome. Each chromosome contains a single, very long molecule of DNA, and there are 46 chromosomes in a typical human cell.
describe neurulation
The ectoderm in the dorsal midline thickens into a neural plate, and then starts to fold inward as a neural groove. This groove deepens until a hollow neural tube is pinched off into the body. Closure of the neural tube begins at the end of week 3 in the region that will become the neck and then proceeds both cranially and caudally. Complete closure occurs by the end of week 4. The cranial part of this neural tube becomes the brain, and the rest becomes the spinal cord.
derivatives of mesoderm
(middle to end of week 3): somites and intermediate mesoderm are segmented and form the segmented structures of the outer tube. Lateral plate mesoderm is unsegmented and is associated with the developing inner tube organs
Somites
The mesoderm closest to the notochord begins as paraxial mesoderm (near the body axis). Starting cranially and proceeding caudally, the paraxial mesoderm divides into a series of blocks called somites. The somites are visible in surface view as a row of subectodermal bulges on each side of the back. The somites are the first body segments, and about 40 pairs develop by the end of week 4.
intermediate mesoderm
This begins as a continuous strip of tissue just lateral to the paraxial mesoderm. Influenced by the segmentation of the somites, the intermediate mesoderm divides into spherical segments in a cranial-to-caudal sequence. Each segment of intermediate mesoderm attaches to a somite.
lateral plate
This, the most lateral part of the mesoderm, remains unsegmented. The lateral plate begins as one layer, but soon splits into two. A wedge of space is formed betwen these two sheets. This space is called the coelom (cavity). The two resulting divisions of the later plate are the somatic mesoderm, next to the ectoderm, and the splanchnic mesoderm (viscera), next to the endoderm. The coelom that intervenes beween the splanchnic and somatic mesoderm will become the serous cavities of the vental body cavity, namely the pertoneal, pericardial, and pleural cavities.
derivatives of ectoderm
The ectoderm becomes the brain, spinal cord, and epidermis of the skin. The early epidermis, in turn, produces the hair, fingernails, toenails, sweat glands, and oil glands of the skin. Neural crest cells, from ectoderm, give rise to the sensory nerve cells. Furthermore, much of the neural crest breaks up into a mesenchyme tissue, which wanders widely through the embryonic body. These wandering neural crest derivatives produce such varied structures as the pigment-producing cells in the skin (melanocytes) and the bones of the face.
derivatives of endoderm
The endoderm becomes the inner epithelial lining of the gut tube and its derivatives: the respiratory tubes, digestive organs, and the urinary bladder. It also gives rise to the secretory cells of the glands that develop from gut-lining epithelium: the thyroid, thymus, and parathyroid glands from the pharynx; and the liver and pancreas from the digestive track.
derivatives of mesoderm and notochord
“mesoderm’s basic parts: the notochord, the segmented portions, the somites and intermediate mesoderm, and the unsegmented somatic and splanchnic lateral plate mesoderm”
derivatives of the notochord
the notochord gives rise to an important part of the spinal column, the springy cores of the discs between the vertebrae. These spherical centers, each called a nucleus pulposus, give the vertebral column some bounce as we walk
derivatives of the segmented mesoderm
“each of the somites divides into three parts. One part is the sclerotome (““hard piece””). Its cells migrate medially, gather around the notochord and the neural tube, and produce the vertebra and rib at the associated level. The most lateral part of each somite is a dermatome (““skin piece””). Its cells migrate externally until they lie directly deep to the ectoderm, whre they form the dermis of the skin in the dorsal part of the body. The third part of each somite is the myotome (““muscle piece””), which stays behind after the sclerotome and dermatome migrate away. Each myotome grows ventrally until it extends the entire dorsal-to-ventral height of the trunk. Myotomes become the segmented trunk musculature of the body wall. Additionally, the ventral parts of myotomes grow into the limb buds and form the muscles of the limbs.<br></br>The intermediate mesoderm, lateral to each somite, forms the kidneys and the gonads. The intermediate mesoderm lies in the same relative location as the adult kidneys, outside the peritoneal cavity, or retroperitoneal.”
derivatives of the unsegmented mesoderm
the splanchnic and somatic lateral plate mesoderm are separated by the coelom body cavity. By now, the splanchnic mesoderm surrounds the endodermally derived gut tube lining. The splanchnic mesoderm gives rise to the entire wall of the digestive and respiratory tubes, except the inner epithelial lining; that is, it forms the musculature, connective tissues, and the slippery visceral serosae of the digestive and respiratory structures. Splanchnic mesoderm also gives rise to the heart and most blood vessels.<br></br>Somatic mesoderm, just external to the coelom, produces the parietal serose and the dermal layer of the skin in the ventral body region. Its cells migrate into the forming limbs and produce the bone, ligaments, and dermis of each limb.
8 weeks after fertilization
crown-to-rump ~3 cm, 2 g at end of period<br></br>head is nearly as large as the body. Nose, ears, and eyes are recognizably human. All major divisions of brain are formed. First brain waves occur in brain stem.<br></br>limbs are formed. Digits are initially webbed but separate by end of week 8. Ossification begins in long bones. Vertebrae are formed in cartilage.<br></br>heart has been pumping since week 4. Liver is large and begins to form blood cells.<br></br>all major organ systems are present in rudimentary form.
9-12 weeks (month 3)
crown-to-rump length ~6 cm at end of period<br></br>brain continues to enlarge. Cervical and lumbar enlargements are apparent in spinal cord. Retina of eye is present.<br></br>trunk and limbs elongate. Palate (roof of mouth) begins to fuse at the midline.<br></br>fetus begins to move, but mother does not feel movement.<br></br>heartbeat can be detected externally. Blood cell formation begins in bone marrow.<br></br>lungs begin to develop. Fetus inhales and exhales amniotic fluid.<br></br>Intestines move into the abdomen. Liver is prominent and producing bile. Smooth muscle is forming in the walls of hollow organs. Pancreas and thyroid have completely formed. Male and female genitalia are distinctive; sex of the fetus can be determined.
13-16 weeks (month 4)
crown-to-rump length: ~11 cm at end of period<br></br>skin development continues with differention of the dermis and subcutaneous tissue. Epidermis at tips of fingers and toes thickens to initiate nail formation. Molanocytes (pigment cells) migrate into the epidermis.<br></br>torso elongates. Bone formation begins in vertebrae. Most bones are distinct, and joint cavities are present. Hard palate is fused.<br></br>myelin begins to form around nerve cells<br></br>glands develop in the GI tract. Meconium is collecting.<br></br>kidneys attain typical structure. Primary follicles containing oocytes begin to form in the ovary (female).
17-20 weeks (month 5)
crown-to-rump length ~16 cm at end of period<br></br>hair follicles and sebaceous and sweat glands form. The body is covered with vernix coseosa (fatty secretions of sebaceous glands), and lanugo (silklike hair) covers the skin.<br></br>brown fat, a site of heat production, forms in the neck, chest, andcrown<br></br>mother can feel fetal movements (quickening)<br></br>the brain grows rapidly
21-30 weeks (month 6 and 7)
crown-to-rump length ~38 cm at end of period<br></br>Period of substantial increase in weight. Fetus has periods of sleep and wakefulness.<br></br>fingernails and toenails are complete. Hair is apparent on the head.<br></br>distal limb bones begin to ossify<br></br>cerebrum grows, and convolutions develop on brain surface to accommodate the increasing size of the cerebral cortex.<br></br>lungs complete development; terminal air sacs and surfactant-secreting cells form at end of month 6.<br></br>bone marrow becomes only site of blood cell formation<br></br>testes descend to scrotum in month 7 (males)
30-38 weeks (month 8 & 9)
crown-to-rump length ~47 cm, 2.7-4.5 kg (6-10 lbs) at end of period<br></br>fat accumulates in subcutaneous tissue; skin thickens<br></br>surfactant production in the lungs increases<br></br>immune system develops
Epithelial tissue occurs in two different forms:
Covering and liing epithelium covers the outer and inner surfaces of most body organs. Examples include the outer layer of the skin; the inner lining of all hollow viscery, such as the stomach and respiratory tubes; the lining of the peritoneal cavity; and the lining of all blood vessels.<br></br>Glandular epithelium forms most of the body glands.
Epithelia functions include:
Protection of the underlying tissues<br></br>Secretion (release of molecules from cells)<br></br>Absorption (bringing small molecules into cells)<br></br>Diffusion (movement of molecules down their concentration gradient)<br></br>Filtration (passage of small molecules through a sieve-like membrane)<br></br>Sensory reception
special characteristics of epithelia
Cellularity<br></br>Specialized cell junctions<br></br>Polarity (apical surface and basal surface)<br></br>Support by connective tissue<br></br>Avascular but innervated (has nerve endings but not blood vessels)<br></br>Regeneration
classification of epithelia
number of cell layers (simple and stratified)<br></br>shape of the cells (squamous, cuboidal, columnar)
classifications of glands
endocrine or exocrine; unicellular or multicullular
classification of multicellular glands
simple glands or compound gland (unbranched or branched duct);<br></br>tubular, aveolar (or acinar), or tubuloalveolar (secretory cells form tubes, spherical sacs, or both)
classes of connective tissue
connective tissue proper (e.g. fat tissue and the fibrous tissue of ligaments); cartilage; bone tissue; blood
special characteristics of connective tissues
Relatively few cells, lots of extracellular matrix.<br></br>Extracellular matrix composed of ground substance and fibers. (3 types of fibers: collagen fibers, reticular fibers, and elastic fibers).<br></br>Embryonic origin (mesenchyme).
primary cell type
fibroblasts (connective tisssue proper); chondroblasts (cartilage); osteoblasts (bone) while secreting matrix, after done they are called fibrocytes, chondrocytes, and osteocytes
areolar connective tissue basic functions
Supporting and binding other tissues<br></br>Holding body fluids<br></br>Defending the body against infection<br></br>Storing nutrients as fat
cell junctions
Three factors act to bind epithelial cells to one another: adhesion proteins in the plasma memranes of the adjacent cells link together in the narrow extracellular space; the wavy contours of the membranes of adjacent cells join in a tongue-and-groove fasion; and there are special cell junctions (characteristic of epithelial tissue but are found in other tissue types as well).
multicellular exocrine gland examples
simple tubular: intestinal glands<br></br>simple branched tubular: stomach (gastric) glands<br></br>compound tubular: duodenal glands of small intestine<br></br>simple alveolar: no important example in humans<br></br>simple branched alveolar: subaceous (oil) glands<br></br>compound alveolar: mammary glands<br></br>compound tubuloalveolar (salivary glands)
primary functions of skin
protection<br></br>body temperature regulation<br></br>excretion<br></br>production of vitamin D<br></br>sensory reception
layers of the epidermis (deep to superficial)
stratum basale (basal layer) (aka stratum germinativum)<br></br>stratum spinosum (spin=spine)<br></br>stratum granulosum (gran=grain)<br></br>strutum lucidum (luci=clear) (only found in thick skin, not thin skin)<br></br>stratum corneum (horny layer) (cornu=horn)
nail parts
distal free edge, a nail plate (the visible attached part), and a root (the proximal part embedded in the skin)
wall of a hair follicle (external to internal)
peripheral connective tissue sheath (fibrous sheath)–derived from the dermis<br></br>glassy membrane–at the junction of the fibrous sheath and the epithelial rooth sheath; in essence the basement membrane of the follicle epithelium<br></br>epithelial rooth sheath–derived from the epidermis; two components: external root theath (direct continuation of the epidermis) and internal rooth sheath (derived from the matrix cells)
rule of nines
way to estimate how much of the body is burned:<br></br>9% front of each leg, back of each leg; 4.5% front of head, back of head, front of each arm, back of each arm; 18% front of trunk, back of trunk, 1% perineum
ABCE(E) rule
a tool to recognize melanoma from moles and new pigment spots:<br></br>Assymetry<br></br>Border irregularity<br></br>Color<br></br>Diameter<br></br>Evolution
comparison of the male and female pelves: female
general structure and functional modifications: tilted forward; adapted for childbearing; true pelvis defines the birh canal; cavity of the true pelvis is broad, shallow, and larger<br></br>bone thickness: bones lighter, thinner, and smoother<br></br>acetabula: smaller; farther apart<br></br>pubic arch: broader (80-90); more rounded<br></br>sacrum: wider; shorter; sacral curvature is accentuated<br></br>coccyx: more movable; straighter<br></br>greater sciatic notch: wide and shallow<br></br>pelvic inlet (brim) wider; oval from side to side<br></br>pelvic outlet: wider; ischial tuberosities shorter, farther apart, and everted
comparison of the male and female pelves: male
“general structure and functional modifications: tilted less far forward; adapted for support of a male’s heavier build and stronger muscles; cavity of the true pelvis is narrow and deep<br></br>bone thickness: bones heavier and thicker, and markings more prominent<br></br>acetabula: larger; closer together<br></br>pubic arch: arch is more acute (50-60)<br></br>sacrum: narrow; longer; sacral promontory more ventral<br></br>coccyx: less movabel; curves ventrally<br></br>greater sciatic notch: narrow and deep<br></br>pelvic inlet (brim): narrow; basically heart-shaped<br></br>pelvic outlet: narrower; ischial tuberosities longer, sharper, and point more medially”
general structure of synovial joints
articular cartilage<br></br>joint (articular cavity)<br></br>articular capsule<br></br>synovial fluid<br></br>reinforcing ligaments<br></br>nerves and vessels
types of synovial joints
nonaxial (adjoining bones do not move around a specific axis)<br></br>uniaxial (movement occurs around a single axis)<br></br>biaxial (movement can occure around two axes; thus the join enables motion along both the frontal and sagittal planes)<br></br>multiaxial (movement can occur around all three axes and along all three body planes: frontal, sagittal, and transverse)
the joint capsule of the knee is reinforced by several capsular and extracapsular ligaments, all of which become taut when the knee is extended to prevent hyperextension of the leg at the knee.
- the extracapsular fibular and tibial collateral ligaments are located on the lateral and medial sides of the joint capsule, respectively. the fibular collateral ligament descends from the lateral epicondyle of the femur to the head of the fibula. the tibial collateral ligament runs from the medial epicondyle of the femur to the medial condyle of the tibia. besides halting leg extension and preventing hyperextension, these collateral ligaments prevent the leg from moving laterally and medially at the knee.<br></br>2. the oblique popliteal ligament crosses the posterior aspect of the capsule. actually it is a part of the tendon of the semimembranosus muscle that fuses with the joint capsule and helps stabilize the joint.<br></br>3. the arcuate popliteal ligament arcs superiorly from the head of the fibula over the popliteus muscle to the posterior aspect of the joint capsule
What ligaments help prevent hyperextension of the knee?
fibular and tibial collateral ligaments<br></br>oblique popliteal ligament<br></br>arcuate popliteal ligament
Cartilages in the adult human body include:
cartilage in the external ear<br></br>cartilages in the nose<br></br>articular cartilages, which cover the ends of most bones at moveable joints<br></br>costal cartilages, which connect the ribs to the sternum (breastbone)<br></br>cortilages in the larynx (voice box), including the epiglottis, a flap that keeps food from entering the larynx and the lungs<br></br>cartilages that hold open the air tubes of the respiratory system<br></br>cartilage in the discs between the vertebrae<br></br>cartilage in the pubic symphysis<br></br>cartilages that form the articular discs within certain movable joints, the meniscus in the knee for example
functions of bones
support<br></br>movement<br></br>protection<br></br>mineral storage<br></br>blood cell formation and energy storage<br></br>energy metabolism
classification of bones
long bones<br></br>short bones<br></br>flat bones<br></br>irregular bones
bone markings categories
projections that are the attachment sites for muscles and ligaments<br></br>surfaces tha tform joints<br></br>depressions and openings
intramembranous ossification
During week 8 of embryonic development, mesenchymal cells cluster within the connective tissue membrane and become bone-forming osteoblasts. These cells begin secreting the organic part of bone matrix, called osteoid, which then becomes mineralized. Once surronded by their own matrix, the osteoblasts are called osteocytes. The new bone tissue forms between embryonic blood vessels, which are woven in a random network. The result is woven bone tissue, with trabeculae arranged in networks. This embryonic tissue lacks the lamellae that occure in mature spongy bone. During this same stage, more mesenchyme condenses just external to the developing membranous bone and becomes the pereosteum. The trabeculae at the periphery grow thicker until plates of compact bone are present on both surfaces. In the center of the membranous bone, the trabeculae remain distinct, and spongy bone results. The final pattern is that of the flat bone.
endochondral ossification, increasing length in long bones
a bone collar forms around the diaphysis<br></br>cartilage calcifies in the center of the diaphysis<br></br>the periosteal bud invades the diaphysis, and the first bone trabeculae form<br></br>diaphysis elongates, and the medullary cavity forms<br></br>epiphyses ossify, and the cartilaginous epiphyseal plates separate diaphysis and epiphyses
healing of a simple fracture
hematoma formation<br></br>fibrocartilaginous callus formation<br></br>bony callus formation<br></br>bone remodeling
four largest sutures
coronal suture, where parital bones meet the frontal bone<br></br>squamous suture, where each pariental bone meets a temporal bone inferiorly<br></br>sagittal suture, where the right and left parietal boones meet superiorly<br></br>lambdoid suture, where the parietal bones meet the occipital bone posteriorly
general structure of vertebrae
the anterior portion of the vertebra is the disc-shaped body. the body is the weight-bearing region of the vertebra<br></br>the vertebral arch forms the posterior portion of the vertebra. it is composed of two pedicles and two laminae. the pedicles are short, bony walls that project posteriorly from the vertebral body and form the sides fo the arch. the two laminae are flat, bony plates that complete the arch posteriorly, extending from the transverse processes to the spinous process. the vertebral arch protects the sinal cord and spinal nerves located in the vertebral foramen<br></br>the large hold encircled by the body and vertebral arch is the vertebral foramen. successive vertebral foramina of the articulated vertebrae form the long vertebral canal, through which the spinal cord and spinal nerve roots pass<br></br>the spinous process is the median, posterior projection arising at the junction of the two laminae. it is an attachment site for muscles and ligaments that move and stabilize the vertebral column.<br></br>a transverso process projects laterally from each pedicle-lamina junction. as with the spinous process, the transverse processes ar eattachment sites for the muscle and ligaments<br></br>articular processes protrue superiorly and inferiorly from the pedicle-lamina junctions and form movable joints between successive vertebrae: the inferior articular processes of each vertebra join with the superior articular processes of the vertebra immediatly inferior. successive vertebrae are joined by both intervertebral discs and by these articlar processes. the smooth joint surfaces of these processes are facets<br></br>notches on the superior and inferior borders of the pedicles form lateral openings between adjacent vertebrae, the intervertebral foramina. spinal nerves from the spinal cord pass through these foramina
sternum landmarks
jugular notch<br></br>sternal angle<br></br>xiphisternal joint
carpals, proximal row (lateral to medial), distal row (lateral to medial)
scaphoid, lunate, triquetrum, pisiform, trapezium, trapezoid, capitate, hamate
“infant’s head during delivery”
“As labor begins, the infant’s head enters the pelvic inlet, its forehead facing one ilium and the back of its head facing the other. If the mother’s sacral promontory is too large, it can block the entry of the infant into the true pelvis.<br></br>Both the coccyx and the ischial spines protrude into the pelvic outlet, so a shaply angled coccyx or unually large ischial spine can interfere with delivery. Generally, after the infant’s head passes through the pelvic intlet, it rotates so that the forehead faces posteiorly and the back of its head faces anteriorly. This is the usualy position of the head as it leaves the mother’s body. Thus, during birth, the infant’s head makes a quarter turn to follow the widest dimensions of the true pelvis.”
tarsals
“talus, calcaneous, cuboid (lateral, ““cube-shaped””), navicular (medial, ““boat-like””), medial, intermediate, and lateral cuneiforms (anterior, ““wedge-shaped””)”
joint classification
functional classification: movement allowed (synarthroses, amphiarthroses, diarthroses)<br></br>structural classification: material that binds the bones together and the presence or absence of a joint cavity: fibrous, cartilaginous, synovial joints
types of fibrous joints
sutures, syndesmoses, gomphoses
types of cartilaginous joints
synchondroses, symphyses
major ligaments extending from the forearm bones to the carpals to reinforce the wrist
palmar radiocarpal ligament (anterior)<br></br>dorsal radiocarpal ligament (posterior)<br></br>radial collateral ligament of the wrist joint (lateral)<br></br>ulnar collateral ligament of the wrist joint (medial)
external ligamentous thickenings of the hip joint capsule reinforce the joint
iliofemoral ligament<br></br>pubofemoral ligament<br></br>ischiofemoral ligament
anterior area of knee joint is covered by three broad ligaments that run inferiorly from the patella to the tibia
“patellar ligament, flanked by the medial and lateral patellar retinacula (““retainers””)”
properties of muscle tissue
contractility<br></br>excitability<br></br>extensibility<br></br>elasticity
function of muscle tissue
produce movement<br></br>open and close body passageways<br></br>maintain posture and stabilize joints<br></br>generate heat
several sheaths of connective tissue hold the fibers of a skeletal muscle together, front external to internal
epiysium<br></br>perimysium<br></br>endomysium
sliding filament mechanism
“initiated by the release of calcium ions from the sarcoplasmic reticulum and the binding of those ions to the troponin molecule on the thin filament. this results in a change of shape of the troponin, which moves the tropomyosin molecule and exposes the binding sites on the actin filament for the myosin heads.contraction results as the myosin heads of the thick filaments attach to the thin filaments at both ends of the sarcomere and pull the thin filaments toward the center of the sarcomere by pivoting inward. after a myosin head pivots at its ‘hinge’, it lets go, returns to its original position, binds to the thin filament farther along its length, and pivots agoin. this ratchet-like cycle is repeated many times during a single contraction. ATP powers this process. the thick and thin filaments themselves do not shorten: the thin filament merely slides over the thick filament”
in the development-based scheme, muscles are organized into groups
muscle of the visceral organs<br></br>pharyngeal arch muscles<br></br>axial muscles<br></br>limb muscles
criteria for naming skeletal muscles
location<br></br>shape<br></br>relative size (maximus-largest, minimus-smallest, longus-long, brevis-short)<br></br>direction of fascicles and fibers (rectus, transversus, oblique)<br></br>location of attachments<br></br>number of origins<br></br>action (flexor, extensor, adductor, abductor)
anterior abdominal wall extends from the costal margin down to an inferior boundary that is defined by the following landmarks
iliac crest<br></br>anterior superior iliac spine<br></br>inguinal ligament<br></br>pubic crest
functions of the nervous system
it uses its millions of sensory receptors to monitor changes occurring both inside and outside the body. each of these changes is called a stimulus, and the gathered information is called sensory input<br></br>it processes and interprets the sensory input and makes decisions about what should be done at each moment, amprocess called integration<br></br>it dictates a response by activating the effector organs, our muscles or glands; the response is called motor output
classification of neurons
structural classification: multipolar neurons, bipolar neurons, unipolar neurons (pseudounipolar neurons)<br></br>functional classification: sensory neurons, motor neurons, interneurons
neuroglia functions
provide a supportive scaffolding for neurons<br></br>cover all nonsynaptic parts of the neurons, thereby insulating the neurons and keeping the electrical activities of adjacent neurons from interfering with each other
neuron/nerve fiber/nerve
a neuron is a nerve cell<br></br>a nerve fiber is a long axon<br></br>a nerve is a collection of axons in the PNS
regeneration of an axon in a peripheral nerve
1) the axon becomes fragmented at the injury site<br></br>2) macrophages clean out the dead axon distal to the injury<br></br>3) axon sprouts, of filaments, grow thorugh a regeneration tube formed by Schwann cells<br></br>4) the axon regenerates, and a new myelin sheath forms
corticle pathway (slower) which follows the spinal pathway works how?
1) parallel processing. simultaneouly, the nerve impulses travel on an axon branch that extends into the white matter. this ascending axon carries the nerve impulses to the brain.<br></br>2) integration in gray matter. multiple interneurons process the nerve impulses to localize the stimulus, identify its source, and plan a resonse. this complex process enables you to feel the pain<br></br>3) voluntary motor response. a nonreflexive motor response is initiated in the gray matter and transmitted down a descending axon in the white matter to stimulate somatic motor neurons
spinal pathway works how?
withdrawal reflex. a painful stimulus triggers nerve impulses in a sensory neuron, which initiate the polysynaptic withdrawal reflex
somatic sensory (SS) sensory components
general: touch, pain, pressure, vibration, temperature, and propreoception from the skin, body wall, and limbs<br></br>special: hearing, equilibrium, and vision
visceral sensory (VS) sensory components
general: stretch, pain, temperature, chemical changes, and irritation in viscera; nausea and hunger<br></br>special: taste and smell
somatic motor (SM) motor components
motor innervation to skeletal muscles
visceral motor (VM; autonomic) motor components
motor innervation to smooth muscle, cardiac muscle, and glands
functional class–neuron type according to direction of impulse conduction: multipolar
most multipolar neurons are interneurons that conduct impulses within the CNS, integrating sesory input or motor output; may be one of a chain of CNS neurons, or a single neuron connecting sensory and motor neurons<br></br>some multipolar neurons are motor neurons that conduct impulses along the efferent pathways from the CNS to an effector (muscle/gland)
functional class–neuron type according to direction of impulse conduction: bipolar
essentially all bipolar neurons are sensory neurons that are locate in some special sense organs. for example, bipolar cells of the retine are involved with the transmission of visual inputs from the eye to the brain (via an intermediate chain of neurons)
functional class–neuron type according to direction of impulse conduction: unipolar (pseudounipolar)
most unipolar neurons are sensory neurons that conduct impulses along afferent pathways to the CNS for interpretation. (these sensory neurons are called primary or first-order sensory neurons)
structural class–neuron type according to the number of precesses extending from the cell body: multipolar
many processes extend from the cell body; all are dendrites except for a single axon
structural class–neuron type according to the number of precesses extending from the cell body: bipolar
two processes extend from the cell body, one is a fused dendrite, the other is an axon
structural class–neuron type according to the number of precesses extending from the cell body: unipolar (pseudounipolar)
one process extends from the cell body and forms central and peripheral processes, which together comprise and axon
relative abundance and location in human body: multipolar
most abundant in body. major neuron type in the CNS
relative abundance and location in human body: bipolar
rare. found in some special sensory organs (olfactory mucosa, eye, ear)
relative abundance and location in human body: unipolar (pseudounipolar)
found mainly in the PNS. common only in dorsal root ganglia of the spinal cord and sensory ganglia of cranial nerves
primary brain vesicles
prosencephalon (forebrain)<br></br>mesencephalon (midbrain)<br></br>phombencephalon (hindbrain)
secondary brain vesicles
presencephalon divides in to the telencephalon (endbrain) and the diencephalon (through-brain)<br></br>mesencephalon remains undivided<br></br>rhombencephalon divides into the metencephalon (afterbrain) and the myelencephalon (brain most like the spinal cord)
telencephalon
develops two lateral swellings that look like large mouse earse . these become the large cerebral hemispheres, together called the cerebrum
diencephalon
develops three main divisions: the thalamus, the hppothalamus, and the epithalamus
mesencephalon
forms the midbrain
metencephalon
ventral part becomes the pons, and the dorsal roof develops into the cerebellum
myelencephalon
forms the medulla oblongata
four parts of the brain
1) brain stem (medulla oblongata, pons, and midbrain)<br></br>2) cerebellum<br></br>3) diencephalon<br></br>4) cerebrum (composed of the two cerebral hemispheres)
functions of the brain stem
it acts as a passageway for all the fiber tracts running between the cerebrum and the spinal cord<br></br>it is heavily involved with the innervation of the face and head; 10 of the 12 pairs of crainal nerves attach to it<br></br>it produces the rigidly programmed, automatic behaviors necessary for survival<br></br>it integrates auditory reflexes and visual reflexes
four pairs of cranial nerves attach to the medulla
vestibulocochlear nerve (crainal nerve VIII)<br></br>glossopharyngeal nerve (cranial nerve IX)<br></br>vagus nerve (cranial nerve X)<br></br>hypoglossal nerve (cranial nerve XII)
brain nuclei in the reticular formation form three columns of gray matter on each side that extend the length of the brain stem
1) the midline raphe nuclei, which are flanked laterally by<br></br>2) the medial nuclear group and then<br></br>3) the lateral nuclear group
“nuclei in the medulla’s reticular formation are involved with visceral activities:”
the cardiac center adjusts the force and rate of the heartbeat<br></br>the vasomotor center regulates blood pressure by stimulating or inhibiting the contraction of smooth muscle in the walls of blood vessels, thereby constricting or dilating the vessels<br></br>the medullary respiratory center controls the basic rhythm and rate of breathing
several cranial nerves attach to the pons
trigeminal (cranial nerve V)<br></br>abducens (crainal nerve VI)<br></br>facial (cranial nerve VII)
each cerebellar hemisphere is subdivided into three lobes:
large anterior and posterior lobes, and the small flocculonodular lobe
information is processed by the cerebellum in the folliwing way:
the cerebellum receives information from the cerebrum on the movements being planned<br></br>the cerebellum compares these planned movements with current body position and movements<br></br>the cerebellum sends instructions back to the cerebral cortex on how to resolve any differences between the intended movements and current position
functions of the hypothalamus
control of the autonomic nervous system<br></br>regulation of body temperature<br></br>regulation of hunger and thirst sensations<br></br>regulation of sleep-wake cycles<br></br>control of the endocrine system<br></br>control of emotional responses<br></br>control of motivational behavior<br></br>forrmation of memory
five major lobes of each cerebral hemisphere:
frontal lobe, parietal lobe, occipital lobe, temporal lobe, insula
information is processed through regions of the cerebral cortex in the following hierarchical manner
- sensory information is received by the primary sensory cortex, and the arrival of this information results in awareness of the sensation<br></br>2. the information is relayed to the sensory association area that gives meaning to the sensory input<br></br>3. the multimodal association areas receive input in parallel from multiple sensory association areas, integrating all of the sensory input to create a complete understanding of the sensory information. these regions also integrate sensory input with past experience and develop a motor response<br></br>4. the motor plan is enacted by the motor cortex
primary somatosensory cortex
receives information from the geeral somatic senses (touch, pressure, vibration, pain, and temperature from the skin and proprieception from the muscles and joints) and enables conscious awareness of these sensations
sensory homunculus
”"”little man””, map of the primary sensory cortex”
contralateral projection
the right cerebral hemisphere receives its sensory input from the left side of the body and the left cerebral hemisphere receives its sensory input from the right side of the body
somatosensory association cortex
lies posterior to and communicates with the primary somatosensory cortex, integrates sensory inputs (touch, pressure, and others) into a comprehensive understand of what is being felt
primary visual cortex
“posterior and medial part of the occipital lobe, much of it buried within the deep carcarine sulcus (““spur-shaped””), receives visual information that originates from the retina of the eye, exhibits contralateral projection”
visual association area
surrounds that primary visual cortex and covers much of the occipital lobe, continues the processing of visual information by analyzing color, form, and movement
primary auditotry cortex
functions in censcious awareness of sound, in relation to loudness, rhythm, and pitch, located on teh superior edge of the temporal lobe, primarily inside the lateral sulcus
auditory association area
lies just posterior and lateral to the primary auditory area, permits the evaluation of a sound
sensory areas
somatosensory areas<br></br>visual areas<br></br>auditory areas<br></br>vistibular (equilibrium) cortex<br></br>gustatory cortex<br></br>olfactory cortex<br></br>visceral sensory area
motor areas (list)
“primary motor cortex<br></br>premotor cortex<br></br>frontal eye field<br></br>Broca’s area”
multimodal association areas (list)
posterior association area<br></br>anterior association area<br></br>limbic association area
basal nuclei (parts)
“caudate ““tail like”” nucleus, putamen ““pod””, globus pallidus ““pale globe”””
meninges (functions)
cover and protect the CNS<br></br>enclose and protect the blood vessels that supply the CNS<br></br>contain the cerebrospinal fluid
meninges (list)
from external to internal: dura mater, arachnoid mater, and pia mater
cerebrospinal fluid (functions)
CSF provides a liquid medium that surrounds and gives buoyancy to the CNS. the brain and spinal cord actually float in the CSF, which prevents these delicate organs from being crushed under their own weight.<br></br>the layer of CSF surrounding the CNS resists compressive forces and cusions the brain and spinal cord from blows and jolts.<br></br>CSF helps to nourish the brain, to remove wastse produced by neurons, and to carry chemical signals such as hormones between different parts of the central nervous system. although similar in composition to the blood plasma from which it arises, CSF contains more sodium and chloride ions and less protein.
CSF circulation
1) CSF is produced by the choroid plexus of each ventricle<br></br>2) CSF flows through the ventricles and into the subarachnoid space via the median and lateral apertures. Some CSF flows through the central canal of the spinal cord.<br></br>3) CSF flows through the subarachnoid space<br></br>4) CSF is absorbed into the dural venous sinuses via the arachnoid granulations
spinal cord (functions)
1) through the spinal nerves that attach to it, the spinal cord is involved in the sensory and motor innervation of the entire body inferior to the head.<br></br>2) through the ascending and descending tracts traveling within its white matter, the spinal cord provides a two-way conduction pathway for signals between the body and the brain.<br></br>3) through sensory and motor integration in its gray matter, the spinal cord is a major center for reflexes.
three funiculi
”"”long ropes””: dorsal (posterior) funiculus, ventral (anterior) funiculus, and lateral funiculus”
four zones of spinal cord gray matter
somatic sensory (SS), visceral sensory (VS), visceral motor (VM), and somatic motor (SM)
features of the ascending and descending pathways:
most pathways cross from one side of the CNS to the other, or decussate, at some point along their course<br></br>most pathways consist of a chain of two or three serially linked neurons that contribute to successive tracts along a given pathway<br></br>most pathways are spatially arranged in a specific way, according to the body region they supply. for example, in one ascending tract, the axons transmitting impulses from the superior parts of the body lie lateral to the axons carrying impulses from the inferior body parts<br></br>all pathways are bilaterally symetrical, occuring on both the right and left side of the brain or spinal cord
three main ascending pathways
spinocerebellar pathway, dorsal column pathway, spinothalamic pathway
In the dorsal column pathway:
the axons of first-order neurons, the sensory neurons, enter the spinal cord and send an axonal branch up one of the dorsal white column tracts, either the medial fasciculus gracilis or the lateral fasciculus cuneatus. these axons ascend in the spinal tract to the medulla oblongata.<br></br>in the medulla oblongata, these axons synapse with second-order neurons in the nucleus gracilis or nucleus cuneatus. axons from these brain nuclei form a tract called the medial lemniscus tract, which decussates in the medulla and then ascends through the pons and midbrain to the thalamus.<br></br>third-order neurons originating in the thalamus send axons to the primary sematosensory cortex on the postcentral gyrus, where the sensory information is processed, resulting in awareness of precisely localized sensations.
In the spiothalamic pathway:
the axons of first-order sensory neurons enter the spinal cord, where they synapse on interneurons in the dorsal gray horn.<br></br>axons of the second-order neurons decussate in the spinal cord, enter the lateral and ventral funicula as the spinothalamic tract, and ascend to the thalamus.<br></br>axons from third-order neurons in the thalamus project to the primary somatosensory cortex on the postcentral gyrus, where the information is processed into the consious sensation. the brain interprets the sensory inforamiton carried by the spinothalamic pathway as unpleasant–pain, burns, cold, and so on.
In the pyramidal tracts:
the axons of pyramidal cells, the upper motor neurons, descend from the cerbral motor cortex through the brain stem to the spinal gray matter–mostly to the ventral horns.<br></br>in the ventral horn, the axons either synapse with short interneurons that activate somatic motor neurons or synapse directly on somatic motor neurons, the lower motor neurons.
indirect motor pathways include:
tectospinal tract (from the superior colliculus, the tectum of the midbrain)<br></br>vestibulospinal tract (from the vestibular nuclei)<br></br>rubrospinal tract (from the red nucleus)<br></br>reticulospinal tract (from the reticular formation)<br></br>these tracts stimulate body movements that are subconscieus, coarse, or postural
classification of receptors
functional classification: according to their location or the type of stimulus they detect<br></br>location of receptors (exteroceptors, interoceptors, proprioceptors)<br></br>stimulus type (mechanoreceptors (e.g. baroreceptor), thermoreceptors, chemoreceptors, photoreceptors, nociceptors)<br></br>structural classification: (free nerve endings) and (encapsulated nerve endings surrounded by a capsule of connective tissue)
main types of encapsulated nerve endings
“tactile (Meissner’s) corpuscles<br></br>lamellar (Pacinian) corpuscles<br></br>bulbous corpuscles (Ruffini endings)<br></br>proprioceptors”
types of joint kenesthetic receptors are present within each joint capsule
lamellar (Pacinian) corpuscles<br></br>bulbous corpuscles (Ruffini endings)<br></br>free nerve endings<br></br>receptors resembling tendon organs
I-XII cranial nerves
I. Olfactory<br></br>II. Optic<br></br>III. Oculomotor<br></br>IV. Trochlear<br></br>V. Trigeminal<br></br>VI. Abducens<br></br>VII. Facial<br></br>VIII. Vestibulocochlear<br></br>IX. Glossopharyngeal<br></br>X. Vagus<br></br>XI. Accessory<br></br>XII. Hypoglossal
components of the brachial plexus, from medial to lateral
Vetral rami. the ventral rami from spinal segments C5-T1 form the roots of the brachial plexus<br></br>Trunks. the ventral rami merge to form three trunks<br></br>Divisions. each trunk splits into two divisions, anterior and posterior<br></br>Cords. these six divisions then converge to form three cords
cerebral cortex function (functional area): frontal lobe
“voluntary movement (primary motor cortex)<br></br>planning movement (premotor cortex)<br></br>eye movement (frontal eye field)<br></br>speech production (Broca’s area)<br></br>executive cognitive functions (anterior association area)<br></br>emotional response (limbic association area)”
cerebral cortex function (functional area): parietal lobe
“general somatic sensation (somatosensory cortex and association area)<br></br>spatial awareness of objects, sounds, body parts (posterior association area)<br></br>understanding speech (Wernicke’s area)”
cerebral cortex function (functional area): occipital lobe
vision (visual cortex and association areas)
cerebral cortex function (functional area): temporal lobe
hearing (auditory cortex and association area)<br></br>smell (olfactory cortex)<br></br>object identification (posterior association area)<br></br>emotional response, memory (limbic association area)
cerebral cortex function (functional area): insula
taste (gustatory cortex)
cerebral white matter function (functional area): commissural fibers
connect the corresponding cortices of the two hemispheres
cerebral white matter function (functional area): association fibers
connect the cortex of the different parts of same hemisphere
cerebral white matter function (functional area): projection fibers
connect the cortex to more caudal parts of the CNS
deep cerebral gray matter function (functional area): basal nuclei (ganglia)
control movements in conjunction with the motor cortex
deep cerebral gray matter function (functional area): basal forebrain nuclei
perform major role in arousal, learning, memory, and motor control; rich in cholinergic fibers
deep cerebral gray matter function (functional area): claustrum
function unclear; may integrate information between the cerebral cortex and the limbic system
brain stem: medulla oblongata
contains project fibers<br></br>site of decussation of the pyramids<br></br>relays ascending sensory pathways transmitting impulses from skin and proprioceptors through nuclei cuneatus and gracilis<br></br>relays sensory information to the cerebellum through inferior olivary nuclei<br></br>contains nuclei of cranial nerves VIII-X and XII<br></br>contains visceral nuclei controlling heart rate, blood vessel diameter, respiratory rate, vomiting, coughing, etc.
brain stem: pons
contains projection fibers<br></br>pontine nuclei relay information from the cerebrum to the cerebellum<br></br>contains nuclei of cranial nerves V-VII<br></br>contains reticular formation nuclei
brain stem: midbrain
contains projection fibers (e.g., cerebral peduncles contain the fibers of the pyramidal tracts)<br></br>contains subcortical motor centers (substantia negra and red nuclei)<br></br>contains nuclei for cranial nerves III and IV<br></br>contains visual (superior colliculi) and auditory (inferior colliculi) reflex centers
brain stem: reticular formation–a functional system
maintains cerebral cortical alertness (reticular activating system)<br></br>filters out repetitive stimuli<br></br>helps regulate skeletal and visceral muscle activity and modulate pain
cerebellum: cerebullum
processes input from cerebral motor cortex, proprioceptors, and visual and equilibrium pathways<br></br>provides output to cerebral motor cortex and subcortical motor centers that result in smooth, coordinated skeletal muscle movements<br></br>resposible for balance and posture
diencephalon: thalamus
relays sensory impulses to cerebral cortex for interpretation<br></br>relays impulses between cerbral cortex and subcortical motor centers, including basal nuclei (ganglia) and cerebellum<br></br>involved in memory processing
diencephalon: hypothalamus
chief inegration center of autonomic (involuntary) nervous system<br></br>regulates body temperature, food intake, water balance, thirst, and biological rythms and drives<br></br>regulates hormonal output of anterior pituitary gland<br></br>acts as an endocrine organ producing posterior pituitary hormones AHD and oxytocin
cerebral hemispheres: cortical gray matter
localizes and interprets sensory inputs<br></br>controls voluntary and skilled skeletal muscle activity<br></br>functions in intellectual and emotional processing
cerebral hemispheres: basal nuclei (ganglia)
subcortical motor centers help control skeletal muscle movements
(multi): limbic system–a functional system
includes cerebral and diencephalon structures (cingulate gyrus, hippocampal formation, amygdaloid body, hypothalamus, and anterior thalamic nuclei)<br></br>mediates emotional respnose<br></br>forms and retrieves memories
somatic motor innervation: somatic motor
targets skeletal muscle<br></br>one-neuron pathway<br></br>1) cell body of the somatic motor neuron is located in the ventral horn of the gray matter<br></br>2) a long myelinated axon extends out from the ventral root to innervate skeletal muscle cells. neurotransmitter is acetylcholine
autonomic innervation: sympathetic division of ANS
targets smooth muscle, cardiac muscle, and glands<br></br>two-neuron pathway, synapse in an autonomic ganglion<br></br>1) cell obdies of preganglionic sympathetic neurons are located in the lateral horn of the gray matter from T1 to L2<br></br>2) the myelinated preganglionic axon synapses with the postganglionic neuron in an autonomic ganglion located adjacent to the spinal column. neurotransmitter is acetylcholine<br></br>3) a long nonmylinated postganglionic axon extends from the autonomic ganglion to the target organ. neurotransmitter is norepinephrine<br></br>4) preganglionic sympathetic axons emerge from T8-L1 to innervate the adrenal medulla, a specialized sympathetic ganglion. adrenal medulla cells release epinephrine and nopepinephrine into blood stream
autonomic innervation: parasymathetic division of ANS
targets smooth muscle, cardiac muscle, and glands<br></br>two-neuron pathway, synapse in an autonomic ganglion<br></br>1) cell bodies of preganglionic parasympathetic neurons are located in the gray matter of the brain stem (CN III, VII, IX, X) and the sacral region of the spinal cord (S2-S4)<br></br>2) the myelinated preganglionic axon synapses with the postganglionic neuron in an autonomic ganglion close to or within the target organ. neutotransmitter is acetylcholine<br></br>3) a short nonmylinated postganglionic axon innervates the target organ. neurotransmitter is acetylcholine
preganglionic axons follow one of three sympathetic pathways:
1) the preganglionic axon synapseswith a postganglionic neuron in the sympathetic trunk ganglion at the same level and exits via the gray ramus communicans into the spinal nerve at that level<br></br>2) the preganglionic axon ascends or descends in the sympathetic trunk to synapse in another thrunk ganglion. the postganglionic fiber exits the sympathetic trunk via the gray ramus communicans at the level of the synapse<br></br>3) the preganglionic axon passes through the sympathetic trunk, exits on a splanchnic nerve, and synapses in a collateral ganglion. the postsynaptic fiber extends from the collateral ganglion to the visceral organ via an autonomic nerve plexus
sensory fibers carrying taste information occur in three cranial nerves
“the facial nerve (VII) transmits impulses from taste receptors in the anterior two-thirds of the tongue<br></br>the glossopharyngeal nearve (IX) carries sensations from the tongue’s posterior third, as well as from the few buds in the pharynx<br></br>the vagus nerve (X) carries taste impulses from the few taste buds on the epiglottis and lower pharynx”
upon receeiving stimuli at synapses with olfactory sensory neurons, mitral cells transmit the impulses along the olfactory tract to
1) the limbic region, where smells elicit emotions<br></br>2) the primary olfactory cortex
neural layer contains three main types of neurons, from external to internal:
photoreceptor cells, bipolar cells, and ganglion cells
vitreous humor functions to:
1) transmit light<br></br>2) support the posterior surface of the lens and hold the neural retina firmly against the pigmented layer<br></br>3) help maintain intraocular pressure (the normal pressure within the eye), thereby counteracting the pulling forces of the extrinsic eye muscles
embryonic development of the eye
a) week 4, early. outpocketing of the diencehpalon forms the optic vesicles<br></br>b) week 4, late. optic vesicles invaginate to form the optic cups. the overlying surface ectoderm thickens to form the lens placode<br></br>c) week 5. lens placode invaginates and forms the lens vesicle<br></br>d) week 6. the neural and pigmented layers of the retina differentiate from the optic cup. central artery reaches tho interior of the eye. mesenchyme derived from neural crest invades<br></br>e) week 7. mesenchyme surrounds and invades the optic cup to form the fibrous and vascular layers and the vitreous humor. lens vesicle forms the lens. surface ectoderm forms the corneal epithelium and the conjunctiva
main parts of the membranous labyrinth:
the semicircular ducts, one inside each semicircular canal. the semicircular ducts contain the sensory receptors for turning movements of the head.<br></br>the utricle and saccule, both in the vestibule. the sensory receptors that monitor position and linear acceleration of the head are located in these portions of the membranous labyrinth.<br></br>the cohlear duct located within the cohlea. the cohlear duct contains the sensory receptors for hearing.
role of the cochlea in hearing
1) sound waves vibrate the tympanic mebrane<br></br>2) auditory ossicles vibrate. pressure is amplified<br></br>3) pressure waves created by the stapes pushing on the oval window move through fluid in the scala vestibuli<br></br>4a) sounds with frequencies below hearing travel trhough the helicotrema and do not excite hair cells<br></br>4b) sounds in the hearing range go through the cochlear duct, vibrating the basilar membrane and deflecting hairs on inner hair cells
embryonic development of the ear
a) 22 days. surface ectoderm adjacent to the neural groove thickens to form otic placodes.<br></br>b) 26 days. invagination of the otic placode forms the otic pit. first branchial groove forms as surface ectoderm invaginates. the endoderm-lined pharynx extends outward, forming the first pharyngeal pouch.<br></br>c) 28 days. otic pits invaginate further until they pinch off from surface, forming the otic vesicles.<br></br>d) weeks 5-8.<br></br>internal ear: membranous labyrinth forms from the otic vesicle; bony labyrinth develops from head mesenchyme.<br></br>middle ear: middle ear cavity and pharyngotympanic tube form from the first pharyngeal pouch.<br></br>external ear: external acoustic meatus develops from first brachial groove.
organs that contain only endocrine cells
pituitary gland at the base of the brain;<br></br>the pineal gland in the roof of the diencephalon;<br></br>the thyroid and parathyroid glands in the neck;<br></br>and the adrenal glands on the kidneys, which contain two distinct endrocrine regions, the adrenal cortex and the adrenal medulla
organs that contain a large proportion of endocrine cells but also function in another organ system
the pancrease falls into this category; it has both endocrine and digestive system functions.<br></br>other organs with major roles in the endocrine system and another organ system include the thymus, which functions in the immune system;<br></br>the gonads in the reproduction system;<br></br>and the hypothalamus in the nervous system. because of its dual functions, the hypothalamus is described as a neuroendocrine organ
organs that contain some endocrine cells
many organs and tissues contain scattered or small pockets of cells that secrete hormones. these include<br></br>the heart,<br></br>the digestive tract,<br></br>the kidneys,<br></br>osteoblasts in bone tissue,<br></br>adipose cells in fat tissues,<br></br>and keratinocytes in the skin
the organs containing endocrine cells can be divided into three groups:
organs that contain only endocrine cells.<br></br>organs that contain a large proortion of endocrine cells but also function in another organ system.<br></br>organs that contain some endocrine cells.
embryonic development of some major endocrine organs
a) week 5. thyroid, thymus, and parathyroid glands form from pharyngeal endoderm. hypophyseal pouch extends superiorly from ectoderm in the roof of the mouth.<br></br>b) week 6. inferior extension of the folor of the diencephalon forms the neurohypophyseal bud.<br></br>c) week 7. hypophyseal pouch pinches off the surface ectoderm and is closely associated with the neurohypophyseal bud.<br></br>d) week 8. hypophyseal pouch forms the anterior lobe of pituitary; neurohypophyseal bud forms the posterior lobe. distinct portions of each differentiate.
short-term stress response
cotecholamines (epinephrine and norepinephrine)<br></br>heart rate increases<br></br>blood pressure increases<br></br>brochioles dilate<br></br>liver converts glycogen to glucose and releases glucose to blood<br></br>blood flow changes, reducing digestive system activity and urine output<br></br>metabolic rate increases
prolonged stress response
(mineralocorticoids)<br></br>kidneys retain sodium and water<br></br>blood volume and blood pressure rise<br></br>(glucorcorticoids)<br></br>proteins and fats converted to glucose or broken down for energy<br></br>blood glucose increases<br></br>immue system suppressed
anterior pituitary release of hormones
hypothalamic hormones released into special blood vessels (the hypophyseal portal system) control the release of anterior pituitary hormones.<br></br>1) when apprpriately stimulated, hypothalamic neurons secrete releasing or inhibiting hormones into the primary capillary plexus.<br></br>2) hypothalamic hormones travel trhough portal veins to the anterior pituitary, where they stimulate or inhibit release of hormones made in the anterior pituitary.<br></br>3) in response to releasing hormones, the anterior pituitary secretes hormones into the secondary capillary plexus. this in turn empties into the general circulation.
posterior pituitary release of hormones
nerve impulses travel down the axons of hypothalamic neurons, causing hormone release from tehir axon terminals in the posterior pituitary.<br></br>1) hypothalamic neurons synthesize oxytocin or antidiuretc hormone (ADH).<br></br>2) oxytocin and ADH are transported down the axons of te hypothalamohypophyseal tract to the posterior pituitary.<br></br>3) oxytocin and ADH are stored in axon terminals in the posterior pituitary.<br></br>4) when associated hypothalamic neurons fire, nerve impulses arriving at the axon terminals cause oxytocin or ADH to be released into the blood.
major components of whole blood
plasma, 55% of whole blood, least dense component<br></br>buffy coat, leukocytes and platelets, <1% of whole blood (formed element)<br></br>erythrocytes, 45% of whole blood, most dense component (formed element)
erythrocytes structural characteristics contribe to respiratory function:
their bioconcave shape provides 30% more surface area than that of spherical cells of the same volume, allowing rapid diffusion of exygen into and out of erythrocytes.<br></br>discounting the water that is present in all cells, erythrocytes are over 97% hemoplobin. without a nucleus or organellse, they are little more than bags of oxygen-carrying molecules.<br></br>erythrocytes lack mitochordria and generate the energy they need by anaerobic mechanisms; therefore, they do not consume any of the oxygen they pick up and are very efficient oxygen transporters
relative abundance of leukocytes
neutrophils (50-70%)<br></br>lymphocytes (25-45%)<br></br>monocytes (3-8%)<br></br>eosinophils (2-4%)<br></br>basophils (.5-1%)
stages of differentiation of blood cells in the bone marrow: effector T cell
hematopoietic stem cell<br></br>lymphoid stem cell<br></br>T lymphocyte<br></br>effector T cell
stages of differentiation of blood cells in the bone marrow: plasma cell
hemotopoietic stem cell<br></br>lymphoind stem cell<br></br>B lymphocyte<br></br>plasma cell
stages of differentiation of blood cells in the bone marrow: platelets
hemotopoietic stem cell<br></br>myloid stem cell<br></br>megakaryoblast<br></br>early megakaryocyte<br></br>late megakaryocyte<br></br>platelets
stages of differentiation of blood cells in the bone marrow: wandering macrophage
hematopoietic stem cell<br></br>myeloid stem cell<br></br>monoblast<br></br>promonocyte<br></br>monocyte<br></br>wandering macrophage
stages of differentiation of blood cells in the bone marrow: neutrophil (granular leukocytes)
hematopoietic stem cell<br></br>myeloid stem cell<br></br>myeloblasts<br></br>promylocites<br></br>neutrophilic myelocyte<br></br>neutrophilic metamyelocyte<br></br>neutrophilic band cell<br></br>neutrophil (granular leukocytes)
stages of differentiation of blood cells in the bone marrow: basophil (granular leukocytes)
hematopoietic stem cell<br></br>myeloid stem cell<br></br>myeloblasts<br></br>promyelocytes<br></br>basophilic myelocyte<br></br>basophilic metamyelocyte<br></br>basophil (granular leukocytes)
stages of differentiation of blood cells in the bone marrow: eosinophil (granular leukocytes)
hematopoetic stem cell<br></br>myeloid stem cell<br></br>myeloblasts<br></br>promyelocytes<br></br>acidophilic myelocyte<br></br>acidophilic metamyelocyte<br></br>eosinophil (granular leukocytes)
stages of differentiation of blood cells in the bone marrow: erythrocyte
hemotopoietic stem cell<br></br>myeloid stem cell<br></br>proerythroblast<br></br>basophilic erythroblast<br></br>polychromatic erythroblast<br></br>orthochromatic erythroblast<br></br>reticulocyte<br></br>erythrocyte
“leukocytes, Wright’s stain”
neutrophil: multilobed nucleus, pale red and blue cytoplastmic granules<br></br>eosinophil: bilobed nucleus, red cytoplasmic granules<br></br>basophil: bilobed nucleus, purplish black cytoplasmic granules<br></br>lymphocyte (small): large spherical nucleus, thin rim of pale blue cytoplasm<br></br>monocyte: kidney-shaped nucleus, abundant pale blue cytoplasm
age-related changes that affect the heart include the following:
hardening and thickening of the cusps of the heart valves.<br></br>decline in cardiac reserve.<br></br>fibrosis of cardiac muscle.
heart development
(days are approximate)<br></br>a) day 20: endothelial tubes begin to fuse<br></br>b) day 22: heart starts pumping<br></br>c) day 24: heart continues to elongate and starts to bend<br></br>d) day 28: bending continues as ventricle moves caudally and atrium moves cranially<br></br>e) day 35: bending is complete
the intrinsic conducting system of the heart
1) the sinoatrial (SA) node (pacemaker) generates impulses<br></br>2) the impulses pause (0.1 sec) at the atroventricular (AV) node<br></br>3) the atrioventricular (AV) bundle connects the atria to the ventricles<br></br>4) the bundle branches conduct the impulses through the interventricular septum<br></br>5) the subendocardial conducting network stimulates the contractile cells of both ventricles
AV valves open; atrial pressure greater than ventricular pressure
1) blood returning to the heart fills atria, pressing tagainst the AV valves. the increased pressure forces AV valves open.<br></br>2) as ventricles fill, AV valva flaps hang limply into ventricles.<br></br>3) atria contract, forcing additional blood into ventricles.
AV valves closed; atrial pressure less than ventricular pressure
1) ventricles contract, forcing blood against AV valve cusps<br></br>2) AV valves close<br></br>3) papillary muscles contract and chordae tendineae tighten, preventing valve flaps from everting into atria
semilunar valves open
as ventricles contract and intraventricular pressure rises, blood is pushed up against semilunar valves, forcing them open
semilunar valves closed
as ventricles relax and intraventricular pressure falls, blood flows back from arteries, filling the cusps of semilunar valves and forcing them to close
blood flow through the heart
systemic capillaries<br></br>to heart (oxygen-poor blood returns from the body tissues back to the heart)<br></br>superior vena cava (SVC)/inferior vena cava (IVC)/coronary sinus<br></br>right atrium<br></br>(tricuspid valve)<br></br>right ventricle<br></br>(pulmonary semilunar valve)<br></br>pulmonary trunk<br></br>to lungs (oxygen-poor blood is carried in two pulmonary arteries to the lungs (pulmonary circuit) to be oxygenated)<br></br>pulmonary capillaries<br></br>to heart (oxygen-rich blood returns tot he heart via the four pulmonary veins)<br></br>four pulmonary veins<br></br>left atrium<br></br>(mitral valve)<br></br>left ventricle<br></br>(aortic semilunar valve)<br></br>aorta<br></br>to body (oxygen-rich blood is delivered to the body tissues (systemic circuit)<br></br>systemic capillaries
four corners of the heart
“the superior right point lies on the right where the costal cortilage of the third rib joins the sternum.<br></br>the superior left point lies at the costal cartilage of the second rib on the left, a finger’s breadth lateral to the sternum.<br></br>the inferior right point lies at the costal cartilage of the sixth rib on the right, a finger’s breadth lateral to the sternum.<br></br>the inferior leftpoint (the apex point) lies on the left in the fifth intercostal stpace at the midclavicular line–that is, at a line extending inferiorly from the midpoint of the left clavicle.”
four functions of the cardiac skeleton
- it anchors the valve cusps<br></br>2. it prevents overdilation of the valve openings as blood pulses through them<br></br>3. it is the point of attachment for the bundles of cardiac muscle in theatria and ventricles<br></br>4. it blocks the direct spread of electrical impulses from the atria to the ventricles. this function is critical for the proper coordination of atrial and ventricular contractions
order of heart valves closing
mitral valve, tricuspid vave, aortic valve, pulmonary valve
the following features distinguish muscular arteries:
the tunica media of muscular arteries is thicker relative to the size of the lumen than that of any other type of vessel. by actively changing the diameter of the artery, this muscular layer regulates the amount of blood flowing to an organ according to the specific needs of that organ.<br></br>the soomth muscle of the tunica media of muscular arteries is sandwiched between two thick sheets of elastin: a wavy iternal elastic membrane forms the outer layer of the tunica intima, and an external elastic membrane forms the outer layer of the tunica media. these elastic membranes, in addition to the thin sheets of elastin found within the tunica media, help to dampen the pulsatile pressure produced by the heartbeat.
the diameter of each arteriole is rugulated in two ways:
1) local factors in the tissues signal the smooth muscle cells to contract or relax, thus regulating the amount of blood sentdownstream to each capillary bed<br></br>2) sympathetic nervous system adjusts the diameter of arterioles throughout the body to regulate systemic blood pressure
capillary functions
deliveroxygen and nutrients cells need<br></br>remove carbon dioxide and nitrogenous wastes that cells deposit into the fluid<br></br>oxygen enters the blood in the lungs<br></br>receive digested nutrients in the small intestine<br></br>pick up hormones in the endocrine glands<br></br>remove nitrogenous wastes from the body in the kidneys
molecules pass into and out of capillaries through four routes
direct diffusion through the endothelial cell membranes.<br></br>intercellular clefts.<br></br>fenestrations.<br></br>pinocytotic vesicles.
veins differ structurally from arteries in the following ways
“the lumen of a vein is larger than that of an artery of comparable size. at any given time, veins hold fully 65% of the body’s blood.<br></br>in a wein, the tunica externa is thicker than the tunica media. in an artery, the tunica media is the thicker layer. in the body’s largest veins–the venae cavae, which return systemic blood to the heart–longitudinal bands of smooth muscle further thicken the tunica externa.<br></br>veins have less elastin in their walls that do arteries because veins do not need to dampen any pulsations (all of which are smoothed out by arteries before the blood reaches the veins).<br></br>the wall of a vein is thinner than that of a comparable artery. blood pressure declines substantially while blood passes through the high-resistance arterioles and capillary beds; thus, blood pressure in the veins is much lower than in the arteries.”
differences in the distributions of arteries and veins:
whereas just one systemic artery leaves the heart (the aorta exiting the left ventricle), three major veins enter the right atrium of the heart: the superior and inferior veae cavae and the coronary sinus.<br></br>all large and medium-sized arteries have deep locations and are accompanie by deep veins, commonly of similarname. in addition, veins are also found just beneath the skin unaccompanied by any arteries. these superficial veins are important clinically because they provide sites for drawing blood or placing an intravenous line. their superficial location also makes them susceptible to cuts or injuries.<br></br>commonly, two or more papllel veins drain a body region rather than a single larger vein. in some regions, multiple veins anastomose to form a venous plexus.<br></br>the brain and digestive tract have unual patterns of venous drainage. veins from the brain drain into dural venous sinuses, which are not typical veins but undothelium-lined channels supported by walls of dura mater. venous blood draining from the digestive organs enters a special subcirculation, the hepatic portal system, and passes through capillaries in the liver before the blood reenters the general systemic circulation.
blood is diverted from the fetal pulmanary circuit through shunts:
forament ovale<br></br>ductus arteriosus
newborn circulation
blood is oxygenated in the lungsn. the heart becomes functionally divided with thefirst breaths. the right side of the heart receives and pumps poorly exygenated blood; thel eft side of the heart receives and pumps highly oxygenated blood.<br></br>1) lungs inflate with first breaths. the resistance in the pulmonary vessels is reduced; blood pressure in the pulmonary circuit falls. blood from the pulmonary trunk follows the path of least resistance into the pulmonary arteries and travels to the lungs to be oxygenated.<br></br>2) foramen ovale and ductus arteriosus close. the increased volume of blood entering the left atrium from the lungs effectively raises the pressure in the atrium, causing the closure of the flaplike valve of the foramen ovale. this structure is now called the fossa ovalis. the ductus arteriosus constricts, closing the shunt to the aorta. the remaining structure is called the ligamentum arteriosum.<br></br>3) the heart is now functionally divided. the left side receives highly oxygenated blood from the lungs and pumps blood through the systemic circuit. the right side receives poorly oxygenated blood from the body and pumps it through the pulmonary circuit.
fetal circulation
blood is oxygenated at the placenta; the fetal lungs are not functioning. fetal circulation has two routes to bypass the pulmonary circuit: the foramen ovale, and opening in the interatrial septum, and the ductus ateriosus, a shunt between the pulmonary trunk and the aorta.<br></br>1) the placenta oxygenates fetal blood. the umbilical vein returns highly exygenated blood to the fetus.<br></br>2) the ductus venosus shunts blood trhough the liver. most of the blood in the umbilical vein bypasses the liver capillaries and is delivered to the inferior vena cava (IVC).<br></br>3) the foramen ovale shunts blood from the right atrium to the left atrium. much of the blood delivered to the right atrium (RA) by the IVC is shunted to the left atrium (LA) via a hole in the interatrial septum, the foramen avale. this blood is pumped out of the left ventricle into the aorta for discribution to the fetal tissues.<br></br>4) the ductus arteriosus diverts blood in the pulmonary trunk to the aorta. blood entering the right atrium from the superior vena cava (SVC) passes into the right ventricle and is pumped into the pulmonary trunk. since fetal lungs are not inflated, resistance is high in the pulmonary arteries. consequently, blood is shunted from the pulmonary trunk to the ductus arteriosus, which connects to the arch of the aorta.<br></br>5) the paired umbilical arterios deliver blood to the placenta. branching off the internal iliac arteries, the umbilical arteries carry blood low in oxygen to the placenta.
