Midterms Flashcards
- Aggregated polyhedral cells
- small amount
- Lining of surface or body cavities; glandular secretion
epithelial
- Several types of fixed and wandering cells
- Abundant amount
- Support and protection of tissues/organs
connective
- Elongated contractile cells
- Moderate amount
- Strong contraction; body movements
muscle
- Elongated cells with extremely fine processes
- Very small amount
- Transmission of nerve impulses
nervous
- Occludins, claudins, ZO proteins
- Actin filaments
- Seals adjacent cells to one another, controlling passage of molecules between them; separates apical and basolateral membrane domains
- Defects in occludins may compromise
the fetal blood–brain barrier, leading to severe neurologic disorders
tight junction
- E-cadherin, catenin complexes
- Actin filaments
- Provides points linking the cytoskeletons
of adjacent cells; strengthens and stabilizes nearby tight junctions - Loss of E-cadherin in epithelial cell tumors (carcinomas) promotes tumor invasion and the shift to malignancy
adherens junction
- Cadherin family proteins (desmogleins, desmocollin)
- Intermediate filaments (keratins)
- Provides points of strong intermediate filament coupling between adjacent cells, strengthening the tissue
- Autoimmunity against desmoglein I leads to dyshesive skin disorders characterized by reduced cohesion of epidermal cells
desmosome
- Integrins
- Intermediate filaments
- Anchors cytoskeleton to the basal lamina
- Mutations in the integrin-β4 gene are linked to some types of epidermolysis bullosa, a skin blistering disorder
hemidesmosome
- Connexin
- Allows direct transfer of small molecules and ions from one cell to another
gap junction
- Lining of vessels (endothelium); Serous lining of cavities: pericardium, pleura, peritoneum (mesothelium)
- Facilitates the movement of the viscera (mesothelium), active transport by pinocytosis (mesothelium and endothelium), secretion of biologically active molecules (mesothelium)
simple squamous
- Covering the ovary, thyroid
- Covering, secretion
simple cuboidal
- Lining of intestine, gallbladder
- Protection, lubrication, absorption, secretion
simple columnar
- Epidermis
- Protection; prevents water loss
stratified squamous keratinized
- Mouth, esophagus, larynx, vagina, anal canal
- Protection, secretion; prevents water loss
statified squamous nonkeratinized
- Sweat glands, developing ovarian follicles
- Protection, secretion
stratified cuboidal
- bladder, ureters, renal calyces
- Protection, distensibility
stratified transitional
- conjunctiva
- protection
stratified columnar
- Lining of trachea, bronchi, nasal cavity
- Protection, secretion; cilia-mediated transport of particles trapped in mucus out of the air passages
pseudostratified
- Elongated secretory portion; duct usually short or absent
- Mucous glands of colon; intestinal glands or crypts (of Lieberkühn)
simple tubular
- several long secretory parts joining to drain into 1 duct
- Glands in the uterus and stomach
branched tubular
- secretory portion is very long and coiled
- sweat glands
coiled tubular
- Rounded, saclike secretory portion
- Small mucous glands along the urethra
acinar
- Multiple saclike secretory parts entering the same duct
- Sebaceous glands of the skin
branched acinar
- Several elongated coiled secretory units and their ducts converge to form larger ducts
- Submucosal mucous glands (of Brunner) in the duodenum
tubular
- ducts converge to form larger ducts
Several saclike secretory units with small ducts converge at a larger duct - exocrine pancreas
acinar
- Ducts of both tubular and acinar secretory units converge at larger ducts
- Salivary glands
tubuloacinar
cells are bound tightly together structurally and functionally to form a sheetlike or tubular structure with little extracellular material between the cells.
epithelium
facing the sheet’s free surface
apical
facing a basement membrane and under- lying connective tissue
basal
Epithelia are often specialized for absorption
transcytosis
thin extracellular layer of specialized proteins, usually having two parts: a basal lamina and a more fibrous reticular lamina
basement membrane
thin meshwork of type IV collagen and laminin produced by the epithelial cells
basal lamina
contains type III collagen and anchoring fibrils of VII collagen, all secreted by cells of the immediately adjacent connective tissue.
reticular lamina
formed by interacting trans- membrane proteins such as claudin and occludin; linear arrangements of these linked proteins surround the apical ends of the cells and prevent paracellular passage of substances
tight junction
formed by interacting proteins of the cadherin family, are points of strong attachment holding together cells of the epithelium.
adherent junction
encircle epithelial cells just below their tight junctions or scattered, spot-like attachment sites called desmosomes or maculae adherens, both of which are attached to cytoplasmic keratins.
zonula adherens
composed of transmembrane integrins attach cells to proteins of the basal lamina.
hemidesmosomes
points of cell contact where both plasma membranes have numerous hexameric complexes of transmembrane connexons, each forming a channel allowing passage of small molecules from one cell to the other.
gap junction
small membrane projections with cores of actin filaments that generally function to increase epithelial cells’ apical surface area for absorption
microvilli
long microvilli with specialized mechanosensory function in cells of the inner ear and for absorption in tissues of the male reproductive tract.
stereocilia
larger projecting structures with a well-organized core of microtubules
cilia
epithelium in which the basement membrane has one cell layer is
simple
Epithelia with two or more layers of cells are
stratified
- move gradually from the basal to the surface layers, changing shape and becoming filled with keratin intermediate filaments.
- cover the body surface, protecting underlying tissues from excess water loss (dehydration) and microbial invasion.
statified squamous
thick and appear to have several cell layers; all cells attach to the basal lamina but not all extend to the free epithelial surface.
pseudostratified epithelia
found only in the lining of the urinary system, is stratified, with large rounded surface cells protective against urine.
transitional
have epithelial ducts carrying secretions to specific sites
exocrine glands
unbranched
simple glands
branched
compound glands
The secretory portions of exocrine glands may form round, saclike ___ or elongated ___
acini; tubules
lack ducts
endocrine glands
three basic secretory mechanisms
merocine, holocrine, apocrine
uses exocytosis
merocrine
terminally differentiated cells filled with lipid product are release
holocrine
apical, product-filled areas of cells are extruded.
apocrine
Exocrine glands producing mucus, or similar individual cells called goblet cells, are called
mucous glands
Exocrine glands producing largely enzymes (proteins) are called ___ and stain darkly with H&E due to the cells’ content of RER and secretory granules.
serous glands
Extracellular fibers and ground substance
fibroblast
Antibodies
Plasma cells
Various immune/defense functions
Eosinophilic leukocytes
Phagocytosis of bacteria
Neutrophilic leukocytes
Phagocytosis of ECM components and debris; antigen processing and presentation
to immune cells; secretion of growth factors, cytokines, and other agents
Macrophages
Pharmacologically active molecules (eg, histamine)
Mast cells and basophilic leukocytes
storage of neutral fats
Adipocytes
- Blood
- Precursor of macrophages
monocyte
- Connective tissue, lymphoid organs, lungs, bone marrow, pleural and peritoneal cavities
- lungs, bone marrow, pleural and peritoneal cavities
Production of cytokines, chemotactic factors, and several other molecules that participate in inflammation (defense), antigen processing, and presentation
macrophage
- Liver (perisinusoidal)
- Same as macrophages
kupffer cell
- Central nervous system
- Same as macrophages
microglial cell
- Epidermis of skin
- Antigen processing and presentation
langerhans cell
- Lymph nodes, spleen
- Antigen processing and presentation
dendritic
- Bone
- Localized digestion of bone matrix
osteoclast
- in connective tissue under various pathological conditions
- Segregation and digestion of foreign bodies
multinuclear giant cell
Resistance to tension
Fibril-Forming Collagens I
Resistance to tension
Fibril-Forming Collagens I
Resistance to pressure
Fibril-Forming Collagens II
structural maintenance in expansible organs
Fibril-Forming Collagens III
Participates in type I collagen function
Fibril-Forming Collagens V
Participates in type II collagen function
Fibril-Forming Collagens XI
Support of epithelial cells; filtration
Network-Forming Collagens IV
Network-Forming Collagens IV
increases density of the matrix
Network-Forming Collagens X
Anchors basal laminae to underlying reticular lamina
Linking/Anchoring Collagens VII
Binds various proteoglycans; associated with type II collagen
Linking/Anchoring Collagens IX
Interacts with type I collagen
Linking/Anchoring Collagens XII
Binds type I collagen fibrils, with types V and XII, strengthening fiber formation
Linking/Anchoring Collagens XIV
- Faulty transcription or translation of collagen type III
- Aortic and/or intestinal rupture
ehlers-danlos type IV
- Faulty lysine hydroxylation
- Increased skin elasticity, rupture of eyeball
ehlers-danlos type VI
- Decrease in procollagen peptidase activity
- Increased articular mobility, frequent luxation
ehlers-danlos type VII
- Lack of vitamin C, a required cofactor for prolyl hydroxylase
- Ulceration of gums, hemorrhages
scurvy
- Change of 1 nucleotide in genes for collagen type I
- Spontaneous fractures, cardiac insufficiency
osteogenesis imperfecta
- Much ground substance; many cells and little collagen, randomly distributed
- Supports microvasculature, nerves, and immune defense cells
- Lamina propria beneath epithelial lining of digestive tract
loose connective tissue
- Little ground substance; few cells (mostly fibroblasts); much collagen in randomly arranged fibers
- Protects and supports organs; resists tearing
- Dermis of skin, organ capsules, submucosa layer of digestive tract
dense irregular connective tissue
- Almost completely filled with parallel bundles of collagen; few fibroblasts, aligned with collagen
- Provide strong connections within musculoskeletal system; strong resistance to force
- Ligaments, tendons, aponeuroses, corneal stroma
dense regular connective tissue
- Sparse, undifferentiated cells, uniformly distributed in matrix with sparse collagen fibers
- Contains stem/progenitor cells for all adult connective tissue cells
- Mesodermal layer of early embryo
mesencyhme
- Random fibroblasts and collagen fibers in viscous matrix
- Supports and cushions large blood vessels
- Matrix of the fetal umbilical cord
mucoid connective tissue
- Delicate network of reticulin/ collagen III with attached fibroblasts (reticular cells)
- Supports blood-forming cells, many secretory cells, and lymphocytes in most lymphoid organs
- Bone marrow, liver, pancreas, adrenal glands, all lymphoid organs except the thymus
reticular connective tissue
Connective tissue is specialized to physically ___ and ___ other tissues and maintain the water required for metabolite diffusion to and from cells.
support ; connect
Connective tissues all consist primarily of ___ material rather than cells.
extracellular
Within most organs connective tissue proper forms the supportive
stroma
supports the organ’s unique functional components
parenchyma
consists of both large protein fibers and nonfibrous areas of unstained ground substance rich in various GAGs and water.
ECM
All adult connective tissues are derived from an embryonic form of connective tissue called ___, which contains uniformly undifferentiated cells scattered in a gel-like matrix.
mesenchyme
major cells of connective tissue proper, are elongated, irregularly shaped cells with oval nuclei that synthesize and secrete most components of the ECM.
fibroblasts
large cells specialized for storage of triglycerides
adipocytes
predominate in a specialized form of connective tissue
adipose tissue
short-lived cells that differentiate in connective tissue from precursor cells called monocytes circulating in the blood; they function in ECM turnover, phagocytosis of dead cells and debris, and antigen presentation to lymphocytes.
macrophages
originate from blood cell precursors and are filled with granules for the release of various vasoactive agents and other substances during inflammatory and allergic reactions.
mast cells
short-lived cells that differentiate from B lymphocytes and are specialized for the abundant secretion of specific anti- bodies (immunoglobulins).
plasma cells
wander through all types of connective tissue proper, providing surveillance against bacterial invaders and stimulating tissue repair.
leukocytes
most important and abundant fibers of connective tissue are composed of the protein
collagen
Upon exocytosis, the non helical ends of the procollagen subunits are removed, forming trimeric
collagen molecules
that aggregate and become covalently bound together in large
collagen fibrils
highly regular assembly of collagens in the fibrils produces a characteristic pattern of
crossbanding
Fibrils of type I collagen are bundled together by other forms of non- fibrillar, linking collagens to produce large
collagen bundles
Collagen fibrils are degraded by collagenase enzymes classified as
MMP
Type III collagen produces a network of delicate ___,
which stain very dark with silver stains and are abundant in immune
and lymphoid tissues.
reticular fibers
composed of the proteins elastin and fibrillin, which exist in a stretchable conformation that provides elastic properties to connective tissues rich in this material.
elastic lamellae
- watery, largely unstained extracellular material
- rich in hydrated GAGs, proteoglycans, and multiadhesive glycoproteins.
ground substance
- The major types of GAGs
- very long polymer of the disaccharide glucosamine glucuronate,
hyaluronan
- shorter chains
- composed of other disaccharide polymers.
sulfated GAG
chondroitin sulfate and keratan sulfate have various sizes and compositions, but they are all bound to the core proteins of ___ and are produced in the Golgi apparatus before secretion.
proteoglycans
Proteoglycans attach to polymers of HA via ___ to form huge complexes in ground substance
linker proteins
allowing temporary attachments between cells and the ECM required for cell migration and positioning.
multiadhesive glycoproteins
loose or dense according to the amount of collagen and ground substance present.
connective tissue proper
(or areolar tissue) has relatively more ground substance than collagen, and it typically surrounds small
loose connective tissue
filled primarily with randomly distributed bundles of type I collagen, with some elastic fibers, providing resistance to tearing from all directions as well as some elasticity.
dense irregular connective tissue
prominent in tendons and ligaments, features bundles of essentially parallel type I collagen, providing great strength (but little stretch) in binding together components of the musculoskeletal system.
dense regular connective tissue
delicate network soft type III collagen and is most abundant in certain lymphoid organs
reticular tissue
gel-like connective tissue
mucoid tissue
- dietary fats pack-aged
- intestine
chylomicrons
- defining cells of adipose tissue (fat)
adipocytes
- triglycerides produced in the liver and circulating
- from fatty acids synthe- sized locally
VLDL
mobilized from adipocytes by hormone-sensitive lipase activated by norepinephrine released from the adrenal gland and various peptide hormones.
lipids
- found in many organs
- 20% of the body weight in adults.
- very large cells
white adipose tissue
Fatty acids are released from white adipocytes by ___ activity when nutrients are needed and carried throughout the body on plasma proteins such as ___
lipase; albumin
polypeptide hormone with target cells in the hypothalamus that is released from white adipocytes and helps regulate eating behavior.
leptin
comprises up to 5% of the newborn body weight but smaller amounts in adults.
brown fat
Fatty acids released in adipocytes of brown fat are metabolized in mitochondria of these cells for
thermogenesis
- Homogeneous, with type II collagen and aggrecan
- Chondrocytes, chondroblasts
- Isolated or in small isogenous groups
- Many components of upper respiratory tract; articular ends and epiphyseal plates of long bones; fetal skeleton
- Provides smooth, low-friction surfaces in joints; structural support for respiratory tract
- Presence of perichondrium
hyaline cartilage
- Type II collagen, aggrecan, and darker elastic fibers
- Chondrocytes, chondroblasts
- Usually in small isogenous groups
- External ear, external acoustic meatus, auditory tube; epiglottis and certain other laryngeal cartilages
- Provides flexible shape and support of soft tissues
- Presence of perichondrium
elastic cartilage
- Type II collagen and large areas of dense connective tissue with type I collagen
- Chondrocytes, fibroblasts
- isolated or in isogenous groups arranged axially
- Intervertebral discs, pubic symphysis, meniscus, and certain other joints; insertions of tendons
- Provides cushioning, tensile strength, and resistance to tearing and compression
fibrocartilage
tough, resilient type of connective tissue that structurally supports certain soft tissues, notably in the respiratory tract, and provides cushioned, low-friction surfaces in joints.
cartilage
- Cells of cartilage, ___, make up a small percentage of the tissue’s mass, which is mainly a flexible mass of extracellular matrix (ECM)
- embedded within lacunae surrounded by the ECM
chondrocytes
includes collagen as well as abundant proteoglycans, notably aggrecan, which bind a large amount of water.
cartilage ECM
- Cartilage always lacks blood vessels, lymphatics, and nerves, but it is usually surrounded by a dense connective tissue ___
- vascularized
perichondrium
three major forms of cartilage:
hyaline cartilage,
(2) elastic cartilage, and
(3) fibrocartilage.
ECM of hyaline cartilage is ___, rich in fibrils of type II collagen and aggrecan complexes with bound water.
homogenous and glassy
less collagen and more proteoglycan immediately around the lacunae, producing slight staining differences in this territorial matrix.
ECM
occur singly or in small, mitotically derived isogenous groups.
chondrocytes
present, but not at the hyaline cartilage of articular surfaces or the epiphyses of growing long bones.
perichondrium
- resembles hyaline cartilage in its chondrocytes and major ECM components, but its matrix includes abundant elastic fibers, visible with special stains, which increase the tissue’s flexibility.
- provides flexible support for the external ear as well as certain structures of the middle ear and larynx; it is always surrounded by perichondrium.
elastic cartilage
- contains varying combinations of hyaline cartilage in small amounts of dense connective tissue
- consists of small chondrocytes
- layered with larger areas of bundled type I collagen with scattered fibroblasts.
- provides very tough, strong support at tendon insertions and in intervertebral discs and certain other joints.
fibrocartilage
All forms of cartilage form from embryonic
mesenchyme
grow by mitosis of existing chondroblasts in lacunae
intenstital growth
formation of new chondroblasts peripherally from progenitor cells in the perichondrium
appositional growth
Repair or replacement of injured cartilage is very slow and ineffective, due in part to the tissue’s
avascularity and low metabolic rate
- Irregular and random arrangement of cells and collagen; lightly calcified
- Developing and growing bones; hard callus of bone fractures
Synonyms - Immature bone; primary bone; bundle bone
woven bone
- Parallel bundles of collagen in thin layers (lamellae), with regularly spaced cells between; heavily calcified
- All normal regions of adult bone
- Mature bone; secondary bone
lamellar bone
- Parallel lamellae or densely packed osteons, with interstitial lamellae
- Thick, outer region (beneath periosteum) of bones
- Cortical bone
compact bone
- Interconnected thin spicules or trabeculae covered by endosteum
- Inner region of bones, adjacent to marrow cavities
- Spongy bone; trabecular bone; medullary bone
cancellous bone
type of connective tissue with a calcified extracellular matrix (ECM), specialized to support the body, protect many internal organs, and act as the body’s Ca2+ reservoir.
bone
differentiate from (stem) osteoprogenitor cells and secrete components of the initial matrix, called osteoid
osteoblasts
allow matrix mineralization to occur.
osteoid
type I collagen, the protein ___, which binds Ca2+ and matrix vesicles with enzymes generating PO4−.
osteocalcin
High concentrations of Ca2+ and PO4− ions cause formation of ___ crystals, whose growth gradually calcifies the entire matrix.
hydroxyapatite
differentiate further from osteoblasts when they become enclosed within matrix lacunae and act to maintain the matrix and detect mechanical stresses on bone.
osteocytes
Osteocytes maintain communication with adjacent cells via a network of long
dendritic process
very large cells, formed by fusion of several blood monocytes, which locally erode bone matrix during osteogenesis and bone remodeling.
osteoclasts
layer of dense connective tissue on the outer surface of bone, bound to bone matrix by bundles of type I collagen called perforating (or Sharpey) fibers.
periosteum
Regions of periosteum adjacent to bone are rich in ___ cells and ___ that mediate much bone growth and remodeling.
osteoprogenitor; osteoblasts
thin layer of active and inactive osteoblasts, which lines all the internal surfaces within bone; osteoblasts here are also required for bone growth.
endosteum
Dense bone immediately beneath the periosteum is called ___; deep to the compact bone are small bony trabeculae or spicules of cancellous (or spongy) bone.
com- pact bone
occur in both the knobby, bulbous ends,
epiphyses
two types of mature bone tissue
epiphyses; diaphysis
intervening shaft
diaphysis
Immature bone, called ___, is formed during osteogenesis or repair and has a calcified matrix with randomly arranged collagen fibers.
woven bone
- By the action of osteoclasts and osteoblasts, woven bone undergoes rapid turnover and is remodeled into
- both compact and cancellous bone
lamellar bone
Most lamellar bone consists of lamellae organized concentrically around small central canals containing blood vessels and nerves; this organization is called
osteon or haversian system
allow all cells to communicate with the central canal.
canaliculi
Bones of the skull and jaws form initially by
intramembranous ossification
osteoprogenitor cells surround and then invade hyaline cartilage models of the skeletal elements in the embryo.
endochondral ossification
diaphyses of fetal long bones form when chondrocytes die after enclosure of the cartilage within a collar of woven bone, creating an initial cavity that is entered by periosteal osteoblasts and vasculature.
primary ossification centers
with cartilage of the epiphyseal growth plate between the primary and secondary ossification sites.
secondary ossification centers
growth plates are the key to ___ during childhood and are organized as an interrelated series of developing zones.
bone elongation
chondrocytes undergo mitosis and appear stacked within elongated lacunae.
zone of proliferation
The most mature chondrocytes in the lacunae swell up, compress the matrix, and undergo apoptosis
zone of hypertrophy
- Spaces created in the matrix
- invaded by osteoblasts, osteoclasts, and vasculature from the primary center.
one of cartilage calcification
woven bone is laid down initially by osteoblasts and remodeled into lamellae bone.
zone of ossification
increases the circumference of a bone by osteoblast activity at the periosteum and is accompanied by enlargement of the medullary marrow cavity.
appositional bone growth
occurs throughout life, with cells and matrix turning over continuously through activities of osteoblasts and osteoclasts.
growth of bones
Lamellae and osteons are temporary structures and are replaced and rebuilt continuously in a process of ___ by which bones change size and shape according to changes in mechanical stress.
bone remodeling
fracture or other injury involves the activation of periosteal fibroblasts to produce an initial soft callus of fibrocartilage-like tissue.
bone repair
soft callus is gradually replaced by a ___ that is soon remodeled to produce stronger lamellar bone.
hard callus of woven bone
key ion for all cells, is stored in bone when dietary calcium is adequate and mobilized from bone when dietary calcium is deficient.
calcium
activity of all three major bone cells and is largely regulated by subtle paracrine interaction among these and other cells.
blood calcium levels
indirectly stimulates osteoclasts to elevate lev- els of calcium in blood,
PTH
inhibit osteoclast activity, lowering blood calcium levels
calcitonin
places where bones meet, orarticulate, allowing at least the potential for bending or movement in that portion of the skeleton.
joints
joints with very limited or no movement
synarthoroses
freely mobile joints
diarthroses
synarthroses in the vertebral column that
cushion adjacent vertebrae.
intervertebral discs
consists of a thick outer layer of fibrocartilage forming a tough annulus fibrosus and a shock-absorbing inner,
gel-like core, the
nucleus pulposus.
ave a joint cavity filled with lubricant synovial fluid,
enclosed within a tough, fibrous articular capsule; ends of the bones involved are covered with hyaline articular cartilage.
Diarthroses
specialized connective tissue of the ___ lines the capsule,
synovial membrane
remove wear-and-tear debris from synovial fluid.
macrophage like synovial cells
synthesize hyaluronan that moves into the synovial fluid with water from local capillaries to lubricate and nourish the articular cartilage.
fibroblast like synovial cells
Chemical structure significantly different from that of other neurotransmitters; active in CNS and in both somatic and autonomic parts of PNS; binds to ACh receptors (cholinergic receptors) in PNS to open ion channels in postsynaptic membrane and stimulate muscle contraction
acetylcholine ACh
Excites activity in neurons to promote cognitive function in the brain (learning and memory); most common neurotransmitter in the brain; opens Na+ channels
glutamate
Synthesized from glutamate; primary inhibitory neurotransmitter in the brain; also influences muscle tone; opens or closes various ion channels
gamma-aminobutryic acid (GABA)
Inhibits activity between neurons in the CNS, including retina; opens Cl– channels
Glycine
Molecules with both carboxyl (—COOH) and amine (—NH2) groups and various R groups; act as important transmitters in the CNS
amino acids
Molecules synthesized from an amino acid by removing the carboxyl group and retaining the single amine group; also called biogenic amines
monoamines
Has various functions in the brain related to sleep, appetite, cognition (learning, memory), and mood; modulates actions of other neurotransmitters
Serotonin or 5-hydroxytryptamine (5-HT)
A distinct group of monoamines
Catecholamines
Produces inhibitory activity in the brain; important roles in cognition (learning, memory), motivation, behavior, and mood; opens K+ channels, closes Ca2+ channels
Dopamine
Neurotransmitter of PNS (sympathetic division of autonomic nervous system) and specific CNS regions
Norepinephrine (noradrenaline)
Has various effects in the CNS, especially the spinal cord, thalamus, and hypothalamus
Epinephrine (adrenaline)
Small polypeptides act as signals to assist in and modulate communication among neurons in the CNS
neuropeptides
Helps regulate response to noxious and potentially harmful stimuli
Enkephalin
Involved in memory regulation and energy balance (increased food intake and decreased physical activity)
Neuropeptide Y
Inhibits activities of neurons in specific brain areas
Somatostatin
Assists with pain information transmission into the brain
Substance P
timulates neurons in the brain to help mediate satiation (fullness) and repress hunger
Cholecystokinin (CCK)
Prevents release of pain signals from neurons and fosters a feeling of well-being
Beta-endorphin
Helps control and moderate the effects of dopamine
Neurotensin
Also part of a nucleotide, inhibits activities in certain CNS neurons
adenosine
Involved in learning and memory; relaxes muscle in the digestive tract; important for relaxation of smooth muscle in blood vessels (vasodilation)
nitric oxide
- Neural tube
- CNS
- Myelin production, electrical insulation
Oligodendrocyte
- Neural tube
- CNS
- Structural and metabolic support of neurons, especially at synapses; repair processes
Astrocyte
- Neural tube
- Line ventricles and central canal of CNS
- Aid production and movement of CSF
ependymal cell
- Bone marrow (monocytes)
- CNS
- Defense and immune-related activities
microglia
- Neural crest
- Peripheral nerves
- Myelin production, electrical insulation
schwann cell
- Neural crest
- Peripheral ganglia
- structural and metabolic support for neuronal cell bodies
satellite cells
Nervous tissue develops in the early embryo when the dorsal ectoderm ___ folds lengthwise to form the neural tube
neural plate
precursor of the CNS,
neural tube
precursors for much of the PNS.
neural crest cells
There are many kinds of neurons, but all consist of a
cell body (perikaryon)
long cytoplasmic extension
axon
one or more shorter processes
dendrites
eurons use the common cell property of excitability to produce and move an ___ along the axon to excite another neuron or other effector cell.
action potential (nerve impulse)
such nerve communication is transmitted to another neuron or effector cell via
synapse
released at the presynaptic membrane and binds receptors on the postsynaptic cell, initiating a new action potential there
neurotransmitter
required to support neurons in many ways, consist of six major types:
glial cells
wrap processes around portions of axons in
the CNS, forming myelin sheath
oligodendrocytes
insulate the axons and
facilitate nerve impulse
myelin sheaths
most numerous cell of the CNS, all produce hundreds of processes to cover and provide regulated microenvironments for neuronal perikarya, synapses, and capillaries.
astrocytes
epithelial-like cells, lacking basement membranes, which line the fluid-filled cerebral ventricles and central canal of the spinal cord.
ependymal cells
mediate immune defense activity within the CNS.
microglia
enclose all axons in nerves of the PNS, producing myelin sheaths around large-diameter axons, whose impulse conductivity is augmented at the nodes of Ranvier between successive Schwann cells.
schwann cells
- located within PNS ganglia
- enclose each perikaryon and regulate its microenvironment.
satellite
regions rich in neuronal perikarya and astrocytes comprise the
gray matter
regions containing tracts of myelinated axons comprise
white matter
large, unique ___ characterize the cortex of the cerebellum
Purkinje neurons
ayers of small ___ form the cerebral cortex.
pyramidal neurons
the tough external
dura natter
- middle layer
- contains much CSF, which helps cushion the CNS within its bony enclosure.
arachnoid layer
delicate ___that directly contacts neural tissue.
pia mater
elaborate folds of vascularized pia mater covered by ependyma that project from walls of the cerebral ventricles; there water is removed from capillaries and transferred into the ventricles as CSF.
choroid plexus
neurons are also protected by the blood-brain barrier,
perivascular feet of astrocytic process
axons from motor neurons (in the spinal cord), sensory neurons, and autonomic neurons
peripheral nerves
thin connective tissue layer immediately surrounding Schwann cells in peripheral nerves, containing a few non-fenestrated capillaries and much reticulin.
Endoneurium
Groups of axons (with Schwann cells and endoneurium) are surrounded by perineurium, consisting of layered, squamous fibroblastic cells joined by tight junctions to make a
blood-nerve barrier.
In large peripheral nerves, groups of axons are subdivided as
fascicles
Surrounding the perineurium is a thick, outermost layer of dense irregular connective tissue,
epineurium
sensory or autonomic, contain neuronal cell bodies and their satellite cells and are surrounded by connective tissue continuous with that of nerves.
ganglia
Certain regions of the CNS, such as near the ependyma, retain rare ___ that allow some replacement of neurons throughout life;
neural stem and progenitor cells
involving formation and remodeling of synaptic connections is also prevalent throughout life.
neural plasticity
neuronal and glial interconnections with the CNS make regeneration and restoration of function within this tissue after major injury very difficult.
complexity & distances
simply organized peripheral nerves have better capacity for ___, a process involving reactivation of the perikaryon, Schwann cells, and macrophages.
axonal regeneration
three major types of muscle
skeletal, cardiac, smooth
very long, multinucleated fibers, cylindrically shaped and with diameters up to 100 μm.
skeletal muscle cells
surrounded by an external lamina and thin connective tissue, endomysium, containing capillaries.
sacrolemma
Groups of fibers called ___ are surrounded by perimysium
fascicles
all fascicles are enclosed within a dense connective tissue
epimysium
muscle fiber is filled with ___, composed of thousands of thick myosin filaments and thin actin filaments
myofibrils
highly organized into contractile units
sarcomeres.
Within sarcomeres thick and thin filaments
interdigitate
project from the thick filaments toward the F-actin
filaments
globular myosin heads
Sarcomeres are separated by___ that bisect the light-staining I bands
Z discs
Between the two I bands of a sarcomere
dark-staining A
band
alternating light and dark bands appear as microscopic ___ along the fibers.
striations
sarcoplasm between parallel myofibrils
mitochondria
- cisternae of smooth ER
- specialized for Ca2+ sequestration and release.
sarcoplasmic reticulum
two terminal cisterns of SR contact a deep invagination of the sarcolemma called a
transverse or t tubule
causes tropomyosin to change shape and allow the myosin heads to bind the actin subunits, forming crossbridges between thick and thin filaments.
ca binding to troponin
myosin heads repeatedly attach, pivot, detach, and return, causing the filaments to slide past one another, shortening the sarcomere.
contraction cycle
Ca2+ is again sequestered, ending contraction and allowing the sarcomeres to lengthen again as the muscle relaxes.
depolarization ends
Synapses of motor axons with skeletal muscle
EMP, NMJ, or myoneural junctions
sensory axons wrap around intrafusal fibers in small specialized fascicles or around myotendinous collagen bundles, respectively.
sensory proprioceptors
Skeletal muscles contain fibers that can be physiologically classified as the three main types:
1) slow, oxidative (type I);
(2) fast, intermediate oxidative-glycolytic (type IIa); and (3) fast, glycolytic (type IIb).
striated, but they consist of individual cylindrical cells, each containing one (or two) central nuclei and linked by adherent and gap junctions at prominent intercalated discs.
cardiac muscle fibers
Contraction of cardiac muscle is ___ at nodes of impulse-gen- erating pacemaker muscle fibers; ___ regulate the rate of contraction.
intrinsic; autonomic nerves
individual small, fusiform (tapering) cells, linked by numerous gap junctions.
smooth muscle fibers
do not form sarcomeres, and no striations are present.
thin and thick filaments
attach to α-actinin located in dense bodies that are located throughout the sarcoplasm and near the sarcolemma; contraction causes cells to shorten individually.
thin actin filament
less well-organized in smooth muscle fibers, and there is no transverse tubule system.
sarcoplasmic reticulum
Conduct blood from heart and with elastic recoil help move blood forward under steady pressure
elastic arteries
Distribute blood to all organs and maintain steady blood pressure and flow with vasodilation and constriction
muscular arteries
Distribute blood to arterioles, adjusting flow with vasodilation and constriction
small arteries
Resist and control blood flow to capillaries; major determinant of systemic blood pressure
arterioles
Exchange metabolites by diffusion to and from cells
capillaries
Drain capillary beds; site of leukocyte exit from vasculature
venules
Collect blood from venules
small veins
Carry blood to larger veins, with no backflow
medium veins
Return blood to heart
large veins
heart has three major layers
(1) endothelium
(2) the myocardium
(3) the epicardium
connective tissue with many adipocytes and covered by mesothelium.
epicardium
stimulates rhythmic contractions and consists of modified cardiac muscle fibers forming the sinoatrial (SA) and atrioventricular (AV) nodes, the atrioventricular bundle (of His), left and right bundle branches, and Purkinje fibers.
cardiac conducting system
located in the subendocardial layer of both ventricles, are distinguished from contractile fibers by their greater diameter, abundant glycogen, and more sparse bundles of myofibrils.
purkinje fibers
Masses of dense irregular connective tissue make up the ___, which surrounds the bases of all heart valves, separates the atria from the ventricles, and provides insertions for cardiac muscle.
cardiac skeleton
isible blood vessels have three major layers or tunics:
- intima
- media
- adventitia
includes the endothelium, connective tis- sue, and an internal elastic lamina in larger vessels;
intima
contains alternating layers of smooth muscle and collagen or elastic lamellae;
media
contains connective tissue, small vessels (vasa vasorum), and nerves.
adventitia
not simply heart and vessel liners; they actively produce factors that prevent blood clotting, factors that cause adjacent smooth muscle cells to con- tract or relax, and factors that initiate inflammation at sites of damage or infection.
endothelial cells
Arteries are grouped by size and wall composition
- large elastic arteries,
- muscular, medium-sized arteries
- small arteries
fenestrated elastic laminae in the thick tunica media
large elastic arteries
fewer than 10 layers of smooth muscle in the media
small arteries
microvasculature too small for surgical manipulation permeates most organs and consists of
- atrioles
- capillaries
- venules
large lumens and thin walls, which drain capillaries.
venules
branch into metarterioles, in which smooth muscle sphincters contract to resist blood flow and relax cyclically to allow pulsatile flow of blood into an anastomosing capillary bed, where metabolic exchange with surrounding cells occurs.
termunal arterioles
Capillaries are classified as three structural and functional types
- continous capillaries
- fenestrated caoillaries
- discontinuous capillaries
many tight junctions so that all exchange must occur through the cells;
continous capillaries
small pores or fenestrations through the cells
fenestrated capillaries
larger lumens, large spaces between the endothelial cells, and a discontinuous basal lamina.
discontinuous capillaries
- endothelium of continuous capillaries and post capillary venules is frequently surrounded by thin cells called
- contractions facilitate blood flow and which can give rise to smooth muscle and connective tissue during microvascular remodeling or repair.
pericytes
Two alternative microvascular pathways
arteriovenous anastomoses; venous portal system
arterioles can bypass a capillary bed,
arteriovenous anastomoses
venules draining a capillary bed quickly branch again to form another capillary bed.
venous portal systems
Interstitial fluid that is not pulled into venules by colloidal osmotic pressure drains as lymph into blind vessels called ___, which have very thin endothelial cell walls with spaces between the cells.
lymphatics
lymph is propelled by movements of surrounding muscles and organs, with intimal valves keeping the flow unidirectional.
lymphatic vessels
largest lymphatic vessels, the___ and right ___, both with walls having tunics like those of veins, return lymph to the circulatory system by joining veins near the heart.
thoracic duct; lymphatic duct
