Histology Flashcards
1
Q
levels of organization
A
1) chemical
2) cellular
3) tissue
4) organ
5) system
2
Q
histology
A
study of microscopic structures of tissues
3
Q
tissue
A
similar cells and cell products that perform a common function
4
Q
types of tissues
A
1) nervous: brain, spinal cord, nerves
2) epithelial: lining of GI organs and other hollow orans, skin surface (epidermis)
3) muscle: cardiac, smooth, skeletal
4) connective: fat and other soft padding, bone, tendon (MAJORITY)
5
Q
hematoxylin & eosin (H&E stains)
A
- hematoxylin: behaves like base, stains basophilic molecules blue (positive charge attracts negative, ex. phosphate groups on nucleic acids)
- eosin: acidic, stains acidophilic molecules pink (negative charge attracts positive, ex. ionized amino groups on proteins)
- together = purply stain
6
Q
epithelial tissue
A
composed of sheets of cells that:
1) cover body surfaces
2) line body cavities
3) form glands
7
Q
external and internal surfaces
A
- external: epidermis
- internal: internal passageways, cavities and fluid-filled chambers
8
Q
endothelium
A
epithelium lining blood cells
9
Q
mesothelium
A
epithelium lining internal body cavities
10
Q
functions of epithelia
A
specific to location:
1) physical protection
2) controls permeability: filtration, absorption, excretion
3) provides sensation: extensively innervated
5) produce secretions: mucus, hormones, enzymes
11
Q
characteristics of epithelia
A
1) cellularity: densely packed cells bound by specialized cell junctions
2) polarity: apical (free), basal and lateral surfaces with specific functions, attached via basement membrane to underlying connective tissue
3) avascular: nutrients diffuse to epithelial cells from connective tissue
4) innervated
5) regenerates
12
Q
components of basement membrane
A
basal lamina (connected to epithelial cells) and reticular lamina (connected to connective tissue)
13
Q
basement membrane characteristics
A
- acellular
- molecules (proteins, collagen) that are secreted by basal epithelial cells and CT cells
14
Q
basement membrane functions
A
1) support epithelium
2) anchor epithelial tissue to CT
3) semipermeable to restrict passage of large molecules
4) scaffold for repair & regeneration: organizes renewal of epithelium following damage
15
Q
basement membrane in retina
A
- healthy retinal microvasculature is dependent on intact BM
- diabetes (hyperglycemia) can alter BM, making it permeable to large molecules
- causes leakage of plasma and lipids = edema, impacts vision
16
Q
microvilli
A
- finger-like extensions, core formed by actin
- apical surface
- abundant where absorption and secretion occur, ex. intestines and kidneys
- number/shape correlated with cell’s absorptive capacity (function to increase SA)
- fuzzy appearance on H&E
17
Q
cilia
A
- long, motile, core formed by microtubules and associated proteins
- apical surface
- respiratory tract, uterine tube -> where things (mucus, oocyte) need to move
- beat in coordinated fashion to move substances
- easier to define on H&E compared to microvilli
18
Q
intercellular connections
A
1) tight junction
2) adherens junction
3) desmosome
4) gap junction
5) hemidesmosome (basal)
19
Q
tight (occluding) junctions aka zona occludens
A
- impermeable seal/band
- binds plasma membrane of cells together
- claudin and occludin (transmembrane proteins that form seal)
- function: tight seal to act as permeability barrier, ensures transcellular transport of molecules, prevents passive flow between cells, limits movement of membrane proteins from one surface to the other
- lateral, close to apical side
20
Q
anchoring junctions
A
- attach cytoskeletons of adjacent epithelial cells together
- transmembrane proteins essential for mechanical strength and stability
- lateral: adherens junctions, desmosomes
- basal: hemidesmosomes
21
Q
adherens junction (zonula adherens)
A
- form adhesion band/belts
- actin microfilaments linked by transmembrane proteins called cadherins
- function to firmly anchor cells, provide strength and distribute shear forces between two cells
22
Q
desmosomes (macula adherens)
A
- forms disc-shaped spots, NOT bands
- link intermediate filaments by cadherins
- function to create strong connections, distribute shear forces
- analogy: rivets on jeans
23
Q
hemidesmosomes
A
- link intermediate filament network on basal surface to BM by integrins
- function to resist separation from BM
24
Q
gap junctions
A
- 6 transmembrane connexins form channels (connexons)
- multiple connexons from adjacent cells align to form junction
- lateral
- function: mediate intercellular communication, permits exchange of small molecules/ions between cells
25
junctional complex
- cell junctions occur together
- ex. in small intestine
- function: divide plasma membrane into apical and basolateral surfaces, organize into correct spots
26
types of epithelium
1) surface: continuous sheets of cells classified by number of layers and shape of cells
2) glandular: specialized cells that secrete substances (2 types: endocrine, exocrine)
27
simple surface epithelia
- one layer of cells all attached to BM
- nuclei at same level
- found in protected areas
28
stratified surface epithelia
- more than one layer
- areas with mechanical or chemical stresses
29
pseudostratified surface epithelia
- appears stratified, but all cells attach to BM
- nuclei at different levels
30
surface epithelia cell shapes
1) squamous: flattened, width > height
2) cuboidal: height = width
3) columnar: nuclei lined up close to BM, height > width
31
simple squamous
- lines vessels (endothelium) and serous lining of cavities (mesothelium)
- function: regulate passage of substances, material exchange (thin, easy to pass)
32
serous meaning
epithelial/connective tissue combined -> produces fluid across membrane
33
simple cuboidal
- surface of ovary, kidney tubules, some glands
- lines surfaces involved in secretion/absorption
34
simple columnar
- lines small intestine, colon, stomach, gall bladder, uterine tube
- secretion/absorption
- larger cells with more organelles than cuboidal
- nuclei lined up
35
pseudostratified columnar
- usually has cilia (aka pseudostratified ciliated columnar)
- respiratory tract, ductus deferens, epididymis
- function: secretion and conduit
- ex. mucus secreted in respiratory tract than swept away by cilia
- nuclei not all at same height
36
stratified squamous
- look to apical layer to identify shape (based on nuclei shape)
- protect against abrasion, water loss, UV and foreign particles
1) keratinized: tough layer of keratin (dead cells, no nuclei), found in skin
2) non-keratinized: lines wet surfaces ex. mouth, esophagus, pharynx, vagina
37
transitional epithelium
- stratified
- bladder, ureters, urethra
- surfaces that change shape (stretch/relax), allows for stretch/recoil
- relaxed: looks like stratified cuboidal, but apical cells are round and large
38
stratified cuboidal
generally rare
39
origin of glandular epithelia
1) simple sheet covering surface
2) invagination (proliferation and downgrowth of cells into CT)
3) disappearance of duct cells for ENDOCRINE glands
40
exocrine vs endocrine
- exo: secretions travel through ducts to surface, continuous with free surface
- endo: ductless that exist within some covering epithelial, secrete into circulation via diffusion through interstitial fluid
41
unicellular exocrine glands
- no ducts
- ex. goblet cells
- secrete mucus onto exposed surface to protect apical surface
- analogy: wine glass
42
multicellular glands
- continuous systems of secreting portion and duct
1) duct: simple (unbranched) or compound (branched)
2) secretory portion: tubular or branched tubular or acinar/alveolar (round, sac-like)
- some differentiate between alveolar and acinar: acinar has smaller lumen
43
exocrine modes of secretion
1) merocrine: exocytosis (most, ex. salivary and pancreas)
2) holocrine: entire vesicle shed into lumen (ex. sebaceous gland)
3) apocrine: pinched off portion of cell secreted (ex. mammary glands)
44
endocrine glands
- secrete cell product into interstitial fluid
- diffuse into circulation
- ex. hormones
45
connective tissue vs epithelia
- never exposed to external environment
- highly vascular
46
basic components of connective tissue
1) specialized cells (few)
2) extracellular fibers
3) ground substance (mostly liquid)
- mostly ECM = 2) and 3)
47
classification of CTs
- based on composition (liquid ex. blood to solid ex. bone) and amounts of basic components
- also determines function
48
functions of CT
1) support, surround, interconnect tissue
2) structural framework for body
3) fluid transport
4) protection
5) energy storage
6) defend body from invasion by microorganisms
49
types of CT
all derived from mesenchymal cells (mesoderm)
1) supportive connective tissue: chondroblasts -> chondrocytes and osteoblasts -> osteocytes
2) fluid connective tissue (ex. blood, lymph)
3) CT proper ("ordinary CT): loose and dense
50
CT proper jello salad analogy
fruit = cells, sugar = fibers, water = ground substance
51
CT proper composition
1) specialized cells: fixed/resident or wandering
2) ECM
52
fixed (resident) cells
- from mesenchymal cells
- formed in and reside in CT
- local maintenance, repair and energy storage -> create favourable environment
53
wandering cells
- from hematopoietic stem cells, differentiate in bone marrow (blood cells)
- migrate into CT
- increase in number with tissue damage or infections
54
types of fixed cells
chondrocytes, adipocytes, fibroblasts, osteocytes
55
fibroblasts
- most common and always present
- spindle-shaped cells
- well developed RER and Golgi complexes
- oval nucleus
- function: produce all CT fibers (collagen, elastin) and ground substance (glycoproteins, proteoglycans)
56
types of wandering cells
B-lymphocytes -> plasma cells, monocyte -> osteoclasts + macrophages, mast cells, basophils, eosinophils, neutrophils
57
scar tissue formation
- fibroblasts typically don't regenerate, but can be stimulated to regenerate CT (ex. damage)
- fill in spaces when tissues cannot be regenerated
58
adipocytes (fat cells)
- lipid storage
- significant flattening of nucleus due to lipid accumulation
- lots of adipocytes = adipose tissue
- tissue slides look empty because they have to be dehydrated in preparation (no fat)
59
plasma cells
- derived from B lymphocytes (WBC)
- large egg shaped cell
- small, eccentric nucleus with "clock face" formed by areas of DNA clumps
- sometimes halo around nucleus formed by large Golgi complex
- basophilic cytoplasm rich in RER
- antibody (proteins) producing cells
60
macrophages
- from monocytes (WBC), mature in tissue spaces
- relatively small and inconspicuous unless they were active in phagocytosis
- specialized names in different organs (microglia in CNS, osteoclasts in bone)
- highly phagocytic, function in ECM turnover, phagocytosis of dead cells, antigen presentation
- ruffled border on electron micrograph, can't see on H&E
61
mast cells
- oval, irregular shaped
- central nucleus
- filled with basophilic granules
- numerous near small blood vessels in skin, mesenteries & tissues lining digestive and respiratory tract (areas where sampling occurs)
- function: localized release of bioactive substances (ex. histamine) important in local inflammation, innate immunity and tissue repair
62
mesenteries
attaches GI tract together
63
metachromasia
granules in mast cells change the colour of basic dyes from blue to purple, stain dark
64
sensitization of mast cells
1) antigen (allergen) invades body
2) plasma cell produces large amounts of IgE antibodies against allergen
3) IgE antibodies attach to mast cells in body tissues (and to circulating basophils)
65
secondary response by mast cells
1) more of antigen invades body
2) antigen combines with IgE attached to mast cells/basophils, triggers degranulation (break down and release of contents), release of histamine and other chemicals
3) histamine causes vasodilation and vessels to become leaky (WBCs and other beneficial things diffuse out); promotes edema; stimulates mucus secretion; smooth muscle contraction
66
leukocytes (white blood cells)
- from circulating blood cells, migrate into CT where they become functional
- increase in number indicates inflammation
- typically only present for a few days, then undergo apoptosis
- granular
67
types of fibers
collagen and elastic
68
collagen
- most abundant protein in body
- strong but flexible, resists shearing and tearing forces
- 3 alpha chain subunits that form fibrils -> fibers -> bundles -> tendon -> muscle
- >28 different types characterized by interacting alpha chain subunits
69
main types of collagen
1) most common, ex. deep within skin, tendon, bONE
2) carTWOlage
3) blood vessels (walls), TH-REEticular fibers
4) meshwork in basement membrane (FLOOR)
70
type 1 collagen
large, wavy appearance
71
Ehlers-Danlos Syndrome
- defects in synthesizing & processing of collagen
- hyperextensible skin, hypermobile joints/trachea
72
type 3 collagen (reticular fibers)
- forms stroma (scaffolding) of highly cellular organs (ex. liver, kidney, adrenal glands)
- parenchyma (functional parts of an organ, or of a structure such as a tumour in the body) arranged on stroma
73
silver stain
common for reticular fibers, stains black
74
elastic fibers
- sparse networks interspersed with collagen bundles in many organs (that allow for stretch, ex. lungs, large BVs)
- elastin embedded in microfibrils composed of fibrillin
- thinner (often) than collagen
- stretch to 1.5x resting length, then recoil
75
ground substance function
- resists compression
- allows for passage of molecules between plasma and interstitial fluid (acts as filter)
- anchors cells within tissues
76
ground substance composition
interstitial fluid (from BVs), glycosaminoglycans (GAGs), proteoglycans, adhesive glycoproteins
77
GAGs
- unbranched carbohydrate chains
- most linked to core protein
- highly negatively charged and hydrophilic
78
hyaluronic acid
- a type of GAG
- unbranched, long and large linear carbohydrate chain
- negatively charged, hydrophilic
79
proteoglycan
- GAGs attached to a core protein
- responsible for gelatinous consistency of ECM
- look like straw cleaner
80
adhesive glycoproteins
- small proteins
- stabilize and link ECM to cell surfaces
81
where does interstitial fluid come from?
- blood plasma
- hydrostatic pressure pushes fluid out of BVs
- oncotic pressure due to large plasma proteins (cannot pass through walls) pulls fluid in
- usually net absorption and secretion at opposite sides of vessel -> homeostasis
- excess fluid that does not return to blood enters lymphatic vessels, becoming lymph
- lymph vessels run alongside BVs and have lowest hydrostatic pressure
82
edema
fluid build-up (excess interstitial fluid)
83
loose (areolar) CT
- several types of cells
- few fibers arranged randomly
- semifluid ground substance
- location: everywhere ex. lamina propria (underneath epithelia) of mucous membranes, around BVs, nerves, organs
- function: support with independent movement of cells and fluid
- most cells are wandering
84
dense regular CT
- mainly collagen type 1
- regular, parallel arrays of fibers with fibroblasts squished between
- location: tendons, ligaments
- function: strong attachment between structures, withstands tension along one direction (long axis of fibers)
85
ligament
bone to bone connection
86
tendon
muscle to bone connection
87
dense irregular CT
- tightly packed, woven, irregularly arranged
- type 1 collagen
- location: fasciae (tissue beneath skin and around muscles), dermis, pericardium, joint capsules, membrane capsules of various organs
- function: tensive (pulling) strength in many directions
88
elastic CT
- mostly elastic fibers with fibroblasts in spaces between
- location: lung tissue, elastic artery walls, trachea, some ligaments between vertebrae
- function: support, allows for stretching, accommodates pressure changes on the walls of arteries closest to heart
89
reticular tissue
- interlacing network of reticular (collagen type 3) fibers and reticular cells (unique fibroblasts found in reticular tissue)
- location: stroma of cellular organs (liver, spleen, lymph nodes, red bone marrow, pancreas)
- function: forms stroma, binds smooth muscle tissue cells, removes blood cells in spleen and microbes in lymph nodes (slow filtration by fiber network)
90
adipose tissue
- specialized fat storing cells (adipocytes)
- location: found with areolar CT, ex. hypodermis of skin, around organs, joints
- function: reduce heat loss through skin, energy reserve, supports and protects (cushioning)
91
cartilage
- supporting CT
- dense network of collagen fibers (support) embedded in ECM
- high concentrations of GAGs and proteoglycans, leads to ground tissue with lots of water
- no nerves
- avascular
92
physical properties of cartilage
- defined by ECM composition
1) firm: tissue can bear mechanical stresses without permanent distortion
2) resilient: resume original shape after deformation (water is fluid)
3) smooth: acts as cushion (ex. for bones)
93
cartilage function
- provide framework for soft tissues, ex. respiratory tract (trachea) and external ear
- withstand tensile (collagen) and compressive forces (water)
- helps facilitate bone movements (glide past each other), ex. articular cartilage in joints
- development and growth of long bones
94
types of cartilage
hyaline, fibro-, elastic -> based on characteristics of ECM
95
chondrocytes
- cartilage cells
- single or in isogenous groups (dividing cells) that are located in lacunae
- synthesize and maintain ECM
96
perichondrium
- dense CT that surrounds most cartilage, not all
- provide nutrients and gases from vessels that diffuse through cartilage ground substance
- also take waste
97
two layers of perichondrium
1) outer fibrous: collagen type 1 and fibroblasts (stains darker)
2) inner cellular: chondrogenic cells that differentiate into chondroblasts, responsible for remodelling ability
98
cartilage ECM composition
- mostly type 2 collagen (a little smaller than type 1)
- ground substance: rich in cartilage specific GAGs linked to core protein, forms proteoglycan monomer called aggrecan
- aggrecan links to hyaluronic acid to create larger aggregates -> attracts lots of water
- ideal for withstanding tensile and compressive forces
99
hyaline cartilage
- most abundant
- ECM: type 2 collagen, gelatinous (proteoglycans and GAGs)
- function: resist compression, flexible support, reduce friction in articulations
- location: ends of bones (articular cartilage), respiratory passages (nose, larynx, trachea), ribs (costal cartilage), embryonic skeleton
- covered by perichondrium EXCEPT articular cartilage
100
elastic cartilage
- similar to hyaline, but has additional rich network of elastic fibers (not glassy)
- more abundant, larger chondrocytes compared to hyaline
- function: strength, elasticity, resiliency and maintaining shape
- location: epiglottis, external ear, auditory tubes
- all has perichondrium
101
fibrocartilage
- thick type 1 collagen fibers that alternate with parallel groups of columns of chondrocytes
- little ground substance
- type 2 collagen also present
- NO perichondrium
- function: resist tension and compression, provide cushioning
- location: pubic symphysis, intervertebral discs, menisci of knee, entheses (tendon and ligament attachment to bone)
102
interstitial growth of cartilage
1) condensation of embryonic mesenchyme; cell projections retract as cells clump together
2) differentiation into chondroblasts
3) chondroblasts separate from one another as they produce ECM (swells with H2O), they become isolated in lacunae
4) multiplication of chondroblasts within matrix gives rise to isogenous groups, isolated chondroblasts become quiescent and maintain matrix as chondrocytes
103
chondroblast vs chondrocytes
- blast: actively building ECM
- cyte: maintaining
- cytes can be stimulated to revert to chondroblasts
104
appositional growth of cartilage
- mesenchymal cells at surface of developing cartilage differentiate into fibroblasts
- fibroblasts secrete type 1 collagen, form outer fibrous layer of perichondrium (therefore, cartilage with no perichondrium cannot have appositional growth)
- inner cellular layer has mesenchymal cells that differentiate into chondroblasts, these secrete matrix onto surface of newly forming chondrocytes
105
bone
- supporting CT
- hard, mineralized ECM containing osteocytes
- matrix is solid, but porous: microscopic extensions through channels allow for diffusion of metabolites and gases, communication
- richly innervated and vascular
- two layers: endosteum (inside) and periosteum, both are involved in remodeling and repair
106
function of bone
1) protect internal organs
2) body movement
3) support soft tissue, provide attachment for muscles
4) mineral/fat storage
5) produce blood cells (hematopoiesis)
107
bone cells
- 2% of body mass
- multipotential mesenchymal cells from bone marrow -> osteoprogenitor cells -> osteoblasts -> osteocytes
- WBCs -> osteoclasts
108
osteoblasts
- bone building cells located on inner and outer surface of bone matrix
- typically form a single layer of cuboidal cells, nucleus often located to one side
- communicate via gap junctions (with other osteoblasts and osteocytes)
- function: produce bone matrix (collagen + organic components, called osteoid, later calcifies)
- become osteocytes once surrounded by ECM
109
osteocytes
- mature bone cells, do not divide
- trapped in lacunae
- extend processes through canaliculi
- function: maintain surrounding bone tissue (nutrient, gas, water exchange), sense mechanical stress, organize remodeling accordingly
110
osteoclasts
- large, multinuclear, derived from combination of several monocytes
- ruffled border with phagocytic activity
- concentrated in endosteum
- function: secrete lysosomal enzymes and acids for osteolysis
111
osteoblast/clast homeostasis
- if disrupted, leads to complications ex. osteoporosis
112
bone ECM composition
- organic matter (osteoid) = 1/3: 95% collagen type 1, glycoproteins and proteoglycans -> tensile strength and flexibility
- inorganic matter = 2/3: osteoid mineralized in the process of matrix formation by inorganic matter, mostly calcium and phosphate hydroxyapatite crystals -> compressional strength
113
bone classifications
based on shape:
1) long: L>W, not necessarily large
2) flat
3) irregular: ex. holes, projections
4) short: somewhat cuboidal
- sesamoid: type of short bone that is within a tendon (largest is patella)
114
long bone characteristics
- shaft (diaphysis)
- 2 ends (epiphyses)
- metaphysis from diaphysis to epiphyseal lines/plates (at both ends)
- medullary cavity filled with marrow
- external surface lined by periosteum (except at ends with articular cartilage)
- internal surface lined by endosteum
115
proximal vs distal
proximal closer to core of body
116
bone marrow
fat storage and blood cell development
117
compact (cortical, dense) vs spongy (travecular) bone
same matrix make-up, different 3D arrangement
118
compact bone structure
- osteon: functional unit, runs parallel to diaphysis
- each osteon consists of:
1) central canal: blood supply, in the middle
2) concentric lamellae: bone matrix strengthened by alternating orientation of collage fibers in adjacent lamellae, wraps around central canal
3) osteocytes: located in lacunae between adjacent lamellae
4) canaliculi: channels that connect lacunae, joining osteocytes and central canal
119
other lamellae in compact bone
1) external circumferential: wraps everything
2) interstitial lamellae: between osteons, fragments of older osteons
3) internal circumferential lamellae: wraps internal spongy bone
*these are not specifically part of the osteon
120
spongy bone structure
- no osetons
- tissue arranged in trabeculae ("beams") oriented along lines of stress (resists compression from many directions)
- trabeculae composed of:
1) parallel lamellae (matrix)
2) osteocytes between
- canaliculi open at surface of trabeculae, gases and nutrients diffuse through tissue to exchange with BVs in red marrow
- red marrow in spaces between trabeculae
121
types of ossification
1) intramembranous: develops from mesenchyme (clavicle, mandible, flat bones in skull)
2) endochondral: bone replaces hyaline cartilage model (bones of limbs, vertebral column, majority of bones)
- both types involve bone matrix forming initially as woven/immature bone, then converting to mature
122
intramembranous ossification
1) mesencyhmal cells become highly vascularized, cluster and differentiate into osteoblasts. multiple ossification centers formed
2) osteoid secreted by osteoblasts undergoes calcification (becomes mineralized)
3) immature/woven bone grows outwards, forming trabeculae. mesenchyme at periphery becomes periosteum. bone growth and angiogenesis occur in parallel
4) continued growth, remodeling, lamellar bone (compact/spongy) replaces trabeculae of immature/woven bone (periosteum deposits bone cells that become compact bone)
123
endochondral ossification
1) development and growth of cartilage model: mesenchymal cells aggregate, develop into chondroblasts, grow interstitially and appositionally in the shape of the bone
2) periosteum and bone collar form: perichondrium around diaphysis converts to periosteum, intramembranous ossification produces bone collar (around diaphysis, cuts off inner chondroblasts, they die and degenerate), matrix calcifies
3) development of primary ossification center: blood vessels invade diaphysis, bringing mesenchymal cells --> differentiate into osteoblasts and blood-forming cells
4) development of medullary cavity: osteoclasts breakdown some spongy bone
5) development of secondary ossification centers: blood vessels invade epiphyses bringing mesenchymal cells, spongy bone forms (two centers at end of bones)
6) formation of articular cartilage and epiphyseal plate: hyaline cartilage remains at epiphyseal plate until early adulthood, responsible for lengthwise growth of bone
124
bone growth (at ends)
- interstitial growth of cartilage and endochondral ossification
1) zone of resting cartilage/reserve: scattered inactive chondrocytes, no growth, anchors plate to ephysis
2) zone of proliferating cartilage: larger chondrocytes in stacks divide, interstitially grow
3) zone of hypertrophic cartilage: large, maturing cartilage, rate of cell division slows, walls of lacunae get thinner (moving away from blood supply)
4) zone of calcified cartilage: chondrocytes die, matrix calcifies
5) zone of ossification: walls break down between lacunae, blood vessels bring osteoprogenitor cells from medullary cavity, these differentiate into osteoblasts/clasts
125
mnemonic for zones of bone growth
Real People Have Career Opportunities
126
young vs adult skeleton
- young: epiphyseal cartilage and plates visible as gaps
- old: no more gaps of cartilage, instead have epiphyseal lines
127
increasing bone diameter
- enlargement by appositional growth
- osteoprogenitor cells of periosteum differentiate into osteoblasts
- at the same time, osteoclasts resorb bone on the inside
- typically in homeostasis
128
subdivisions of nervous system
1) CNS: brain enclosed in cranium, spinal cord enclosed in vertebral column
2) PNS: cranial nerves from brain/brainstem, spinal nerves from spinal cord
129
functions of the nervous system
1) sensory nervous system: detect afferent input from soma/viscera, transmit to CNS receptors
2) CNS processes sensory input and determines response (integration)
3) motor nervous system: receive output efferent signals, PNS transmits to somatic/visceral motor effectors
130
somatic nervous system
- voluntary, consciously controlled, perceived
- exception is reflexes
- input from: skin, muscle, joints via sensory neurons
- output to: skeletal muscle via somatic motor neurons
131
autonomic nervous system
- involuntary maintenance of homeostasis
- input from: blood vessels, internal organs via sensory neurons
- output to: cardiac muscle, smooth muscle, glands via visceral motor neurons
- divided into PNS/SNS
132
cells of nervous system
1) neurons
2) glial cells
133
neuron characteristics
- communication cells
- excitable, conductivity
- high metabolic rate, require glucose and oxygen
- extreme longevity
- non-mitotic, except in some areas of brain and olfactory neurons
- components of typical neuron: cell soma (lots of RER for neurotransmitter, cytoskeleton), dendrites, axon
134
parts of a neuron
1) dendrites: conduct electrical signals from other cells towards cell body
2) cell body: nucleus and organelles
3) axon: transmits impulses, may be myelinated
4) axon terminals: communicate with other neurons
135
neurons on H&E stains
- axon hillock: longer than dendrites, doesn't stain as dark because no chromatophilic substance
- nucleus, dendrites, glial cells visible
- NS: chromatophilic substance (free and bound ribosomes), aka Nissl bodies
136
structural classification of neurons
1) bipolar: two extensions from soma
2) multipolar: >2
3) pseudounipolar: one
137
functional classification of neurons
1) sensory: afferent signals to CNS, most pseudounipolar, posterior, cell body in PNS
2) inter: only in CNS, connect sensory and motor neurons, multipolar, most numerous
3) motor: efferent signals to effectors, multipolar, anterior, cell body in CNS
138
posterior, anterior
posterior/dorsal = closer to back of body (vs anterior/ventral)
139
types of stains for neural tissue
1) Golgi: stains some neurons only, but stains entire neuron
2) Nissl: only stains cell bodies
3) myelin
4) H&E: cell bodies, glial cells, often difficult to see axon
140
types of glial cells
- CNS: astrocytes, oligodendrocytes, ependymal cells, microglia
- PNS: neurolemmocytes (Schwann cells), satelite cells
141
astrocytes
- large cell, several cell processes that contact BVs and neurons with end feet, look like stars
- most abundant and diverse
- form structural network
- functions: replace damaged neurons by clumping to form a glial scar, regulate tissue fluid composition, regulate synaptic transmission (removal of neurotransmitters), neuronal development, blood brain barrier
- gold chloride stain
142
oligodendrocytes
- rounded, bulbous cell with slender cytoplasmic extensions
- extensions wrap around many axons to form myelin sheath in CNS
- predominant glial cell in white matter
- function: increase rate of axonal conduction
143
ependymal cells
- simple cuboidal epithelial cells with microvilli and cilia
- line ventricles of brain and central canal of spinal cord (cavities filled with CSF in CNS)
- function: produce, monitor and circulate CSF
144
microglia
- small cell with slender branches from body (also star-like)
- migrate through CNS to areas of inflammation
- function: replicate, secrete cytotoxic factors which kill bacteria, phagocytize dead cells
- essentially the macrophages of CNS
145
neurolemmocytes
- same function as oligodendrocytes
- form myelin sheath around ONE axon in PNS
- several needed to myelinate an entire axon
- leave nodes of ranvier (neurofibril nodes), current skips from one to the next
- consists mainly of plasma membranes (lots of fat)
146
myelination process in PNS
1) neurolemmocyte encloses segment of axon within a groove
2) rotates around axon
3) inner layers of cell membrane compressed, cytoplasm forced into more superficial layers
147
satellite cells
- flattened cells that surround neuronal cell bodies in ganglia (collection of cell bodies in PNS)
- function: regulate cellular exchange between neurons and their environment
148
grey matter in CNS
- neuronal cell bodies predominate
- appears grey due to absence of myelin
- function: location where synaptic transmission occurs
- brain: in cortex (outer portion) and nuclei (deep within brain)
- spine: anterior and posterior horns
149
grey matter in CNS on a micrograph
- small glial cell bodies (can't tell what type)
- multipolar neuron cell bodies (pyramidal cells)
- everything else = neuropil: network of nerve fibers, neuronal and glial cell processes
150
white matter in CNS
- axons (tracts, columns, pathways), glial cell bodies, vessels
- appears white due to myelination
- function: ascending tracts carry sensory info, descending tracts carry motor info
151
white matter in CNS on micrograph
- same things: multipolar neuron cell body, neuropil, glial cell bodies
- white spaces from oligodendrocytes (drained fat)
152
grey matter in PNS
- neuronal cell bodies
- sensory ganglia: pseudounipolar sensory neurons, both somatic and visceral
- autonomic ganglia: multipolar autonomic motor neurons
153
sensory (dorsal root) ganglion on H&E
- central nucleus
- large cell bodies
- surrounded evenly by satellite cells
154
autonomic ganglion on H&E
- irregular outline
- smaller eccentric nucleus
- few satellite cells
155
white matter in PNS
- one nerve fiber = axon + myelin sheath (if present)
- fascicle: group of fibers
nerve: collection of fascicles
- enclosed by connective tissue layers:
1) endoneurium: around each axon
2) perineurium: around each fascicle
3) epineurium: around entire nerve
156
types of muscle tissue
1) skeletal: voluntary, striated
2) smooth: involuntary, non-striated
3) cardiac: involuntary, striated
157
skeletal muscle development
1) myoblasts fuse to form myotubes
2) satellite cells also develop (reserve of progenitor cells, produce new cells after injury, can regenerate)
3) myotubes differentiate into fibers: multinucleated, nuclei pushed to the side
158
skeletal muscle fiber characteristics
long, cylindrical, multinucleated
159
organization of skeletal muscles
1) muscle fiber: myofibrils within sarcoplasm
1a) wrapped with endomysium
2) fascicle: many muscle fibers
2a) perimysium
3) epimysium wraps entire muscle
4) tendon attaches to bone
160
purpose of CT organization in muscle cells
- organize fibers
- ensure uniform contraction
- hold them in place
- veins, arteries and nerves branch within CT to reach individual muscle fibers
161
tendon characteristics
- can be seen on gross level
- connects muscle to bone (for movement)
- collagen fibers of epi, peri, endomysium blend with those of tendon for attachment
- collagen fibers of tendon interweave with collage in periosteum, cement to bone matrix as perforating fibers
162
skeletal muscle cross section (transverse)
- small size of nuclei relative to cell size
- adjacent cells surrounded by CT
- multinucleated
- nuclei pushed to side
163
skeletal muscle longitudinal section
- striations
- nuclei pushed to periphery
164
sarcolemma
cell membrane of skeletal muscle fiber
165
sarcoplasm
- cytoplasm of skeletal muscle fiber
- contains glycogen: ATP stores
- contains myoglobin: O2 stores
166
sarcoplasmic reticulum
- ER of skeletal muscle fiber
- stores Ca2+
167
transverse tubules (T-tubules)
tubular extensions of sarcolemma perpendicular to cell surface
168
terminal cisterna
expansions of SR on either side of T tubules
169
triad
pair of cisterna + T-tubule
170
myofilaments
small contractile protein filaments (actin, myosin)
171
myofibril
run the length of the muscle fiber, consist of bundles of myofilaments
172
sarcomere
- functional unit of striated muscle fibers
- regular arrays of actin and myosin filaments (these result in the striations)
173
myofilament: thin filament
- F-actin and associated proteins
- F-actin is 2 rows of 300-400 G-actin (globular)
- increase in Ca = conformational change in troponin = shift of tropomyosin = exposes active site of G-actin that can bind myosin
174
myofilament: thick filament
- 2 elongated proteins wound together
- ~300 myosin molecules bundled together to form a thick filament
- each ahs globular head and elongated tail
- head binds F-actin to create cross bridges
- tail points towards M line
175
sarcomere organization (MHA ZI)
- Z disc: delineates sarcomere and attachment for thin filaments, which extend towards M line
- M line: attachment for thick filaments
- I band: extend both directions from Z disc, contain only thin filaments
- A band: extends length of thick filaments & includes parts of thin filaments that overlab
- H zone: central portion of A band, thick filaments only
176
how does sarcomere change as muscle contracts?
- length of sarcomere shortens
- I band decreases
- A band stays the same
- H zone decreases
177
neuromuscular junction
- synapse between somatic motor neuron and muscle fiber
- includes terminal synaptic knob, synaptic cleft and motor end plate
178
muscle contraction initiation process
1) nerve impulse causes Ach release from synaptic knob into synaptic cleft
2) Ach binds receptors on motor endplate, opens ligand-gated ion channels (Na+), triggers AP
3) AP propagates along sarcolemma into T-tubules,
4) Ca released from terminal cisternae, leading to muscle fiber contractions (cross bridge formation, myosin head pivots and pulls Z discs towards M line)
5) cyclic events (detach, return, repeat) continue as long as Ca is present
179
muscle contraction ending process
1) Ach diffuses out or is removed by acetylcholinesterase
2) SR recaptures Ca
3) active sites covered, no more crossbridging
4) contraction ends
5) relaxation occurs (passive return to resting length due to elasticity, pull of antagonistic muscles and gravity)
180
how does botox work?
- causes muscle relaxation by preventing Ach release
181
motor unit
single motor neuron + all muscle fibers it controls
182
relationship between control and force in motor units
- control inversely proportional to size of motor unit
- force proportional to number of activated motor units
183
muscle tone
- some motor units always active (tension, but not enough for movement)
- avoid fatigue by rotating motor unit activation
- resting tone stabilizes position of bones and joints (ex. postural muscles)
- movement can require overcoming muscle tone
184
types of skeletal muscle
1) slow-twitch: aerobic ATP generation
2) fast-twitch: anaerobic ATP generation
185
compare and contrast slow/fast twitch muscles
slow (endurance)
- slow ATP use
- high ATP production capacity, aerobic
- high concentration of capillaries
- high myoglobin
- red because of myoglobin
- lots of mitochondria
- high resistance to fatigue
fast (short duration)
- all opposites
186
slow vs fast muscle on micrograph
slow = smaller diameter, darker colour
fast = larger diameter, paler
187
skeletal muscle hypertrophy
- repeated stimulation results in:
1) more mitochondria
2) more glycogen reserves
3) more glycolytic enzymes *all to increase ATP generation
4) more myofibrils with more myofilaments
188
cardiac muscle characteristics
- short, branched cells
- single central nucleus
- intercalated discs
- no myosatellite cells, so cannot regenerate
- aerobic respiration
- lots of mitochondria
- myoglobin reserves
- lipid droplets and glycogen granules as energy reserves
189
intercalated disc
- specialized cell junctions (skeletal muscle has no junctions)
- irregular intervals
- gap junctions: intercellular ionic communication (pace-maker cells set rate of contraction and these communicate the impulse)
- desmosomes and fascia adherens: strong connection
- ensure coordinated contraction
190
key features of cardiac muscle
- rich supply of blood vessels
- centrally placed, single nucleus (most noticeable in transverse section)
191
smooth muscle characteristics
- specialized for slow, steady contractions
- walls of BVs, digestive, respiratory, urinary and reproductive organs
- small, fusiform (spindle-shaped) cells with single central oval nucleus
- pacesetter cells set rate of contractions
- signals propagate via gap junctions
- can hypertrophy
- capacity to regenerate
- no consistent pattern of thick/thin filament
- may not see nucleus in transverse section
192
blood function
1) transportation: gases, nutrients, hormones, waste products
2) maintenance of homeostasis: pH, body temp, osmotic pressure
3) protection: clotting, WBCs, proteins (antibodies)
193
formed elements
cells + cell fragments
194
components of blood
1) plasma (55%):
- 91.5% water
- 8.5% solutes: proteins (albumins, globulins, fibrinogens), electrolytes
2) buffy coat (<1%): white blood cells and platelets
3) red blood cells (45%)
195
types of white blood cells
1) agranulocytes: lymphocyte, monocyte
2) granulocytes: neutrophil, basopphil, eosinophil
196
Wright stain
- several dyes that dye different parts of blood different colours
- WBCs: nuclei and granules stained
- RBCs stained
- platelets stained
197
erythrocyte characteristics
- no nuclei or typical organelles (so not really cells)
- largely cytoskeleton and cytoplasm (2/3 water, 1/3 protein)
- biconcave disc shape: helps line up, flexible, large SA/V ratio to carry more oxygen
- 120 day life cycle (wear and tear, cannot synthesize new components, non dividing)
- eventually recycled
198
hematocrit
fraction (volume) of blood occupied by RBCs (average 50-60%)
199
rouleaux
stacked RBCs
200
hemoglobin (Hb)
- ~270 million on one RBC
- 4 globular protein subunits (2 alpha, 2 beta) --> AAs bind CO2 weakly (~23%, rest transported as bicarbonate)
- 4 non-protein pigments (hemes)
- iron (Fe2+) in middle of each heme --> associates with O2
201
sickle cell disease
- beta globin chain mutated
- when gives up O2, forms stiff, long, rod-like structure (sickle cell)
- ruptures easily
202
blood typing
- characterized by presence or absence of antigens on plasma membrane on RBCs
- A, B, O --> antibodies made without prior exposure
- Rh (D) --> +/-, normally no antibodies until exposure (sensitization)
203
blood typing process
1) mix drops of blood with different antisera
2) agglutination indicates presence of that antigen
3) ABO and Rh+ typically reported together
204
leukocyte characteristics
- circulate in blood and are scattered in peripheral tissues (most in tissues)
- defend body against pathogens, remove waste and damaged cells
- short life span, die in CT (apoptosis)
- diapedesis: migrate into tissues in response to chemotactic signals and changes in endothelial cell surface receptors (induced by acute inflammation)
205
NEVER LET MONKEYS EAT BANANAS
most to least abundant: neutrophils, lymphocytes, monocytes, eosinophils, basophils
206
neutrophils
- 50-70%
- 1 nucleus, multiple lobes
- pale granules (lysosomal enzymes and bactericidal compound)
- function: kill and phagocytose bacteria, breakdown releases chemotactic signals
207
lymphocyte
- 20-25%
- small or big round, heterochromatic nucleus
- little cytoplasm
- few in blood, most in peripheral tissues and lymphatic system
- only WBCs that recirculate
- function: specific immunity (B, T, NK cells)
208
monocytes
- 3-8%
- kidney shaped nucleus
- clear cytoplasm
- largest WBC
- circulate for a few days, enter CT spaces, differentiate into macrophages
- function: phagocytose dead cells, antigens and bacteria; release chemotactic agents to attract other phagocytes
209
eosinophils
- 2-4%
- bilobed nucleus
- bright orange-red granules (eosin)
- function: attracted to antigen/antibody complexes and parasitic worms
- increase in number with allergic reaction and parasitic infections
210
basophils
- <1%
- bilobed nucleus, often obscured by basophilic granules
- modulate inflammation
- accumulate within damaged tissues, discharge granules into interstitial fluid
- granules: histamine (vasodilation, capillary permeability, bronchoconstriction), heparin (anticoagulant), chemotactic factors
211
platelets
- small membrane bound cytoplasmic fragments, no nucleus
- shed by megakaryocytes in red bone marrow
- life cycle 10-12 days, continually replaced
- important in blood clotting (hemostasis): initiate/control by enzyme release, form temporary plug, involved in active contraction of formed clot
212
cardiovascular system
- heart, blood vessels, blood
- heart = double pump: pulmonary circuit from right side, systemic from left
- gas exchange at tissue level across capillaries
- closed system
213
arteries vs veins
- arteries away from heart, veins towards heart
- arteries: thin elastic membranes in media and intima
- arteries remain open when cut, can spring back into shape, can withstand changes in BP
- arteries have no valves
214
blood vessel wall layers
1) tunica externa (adventitia): loose CT, anchors to surrounding structures, contains vasa vasora (own blood supply) in larger vessels
2) tunica media: circular arranged smooth muscle, may have external elastic lamina, SNS controls diameter
3) tunica intima: endothelium + BM & subendothelial layer of loose CT, may have internal elastic lamina, forms valves
215
elastic arteries
- largest arteries, closest to heart
- tunica externa : contains vasa vasorum
- media: thick, contains fenestrated sheets of elastin between layers of smooth muscle
- intima: relatively thick
- function: conduct blood away during systole, propel blood between contractions (elastic recoil), modulate changes in BP during cardiac cycle
216
muscular (distributing, medium-sized) arteries
- externa: thick, often separated from media by external elastic lamina
- media: more smooth muscle, less elastin (maintains shape in cross section)
- interna: thin, prominent internal elastic lamina
- function: distribute blood to tissues and organs according to tissue demands
217
small arteries vs arterioles
- number of smooth muscle layers
- small arteries: 3-8
- arteriole: 1-2
218
arterioles
- no elastic laminae
- inconspicuous externa
- terminal end called metaarteriole
- function: regulate flow into capillary beds through changes in vascular resistance (SNS, local conditions, hormones)
219
metaarteriole
- smooth muscle fibers act as sphincters and produce periodic blood flow into capillaries
220
capillaries
- smallest BVs (lumen a bit smaller than RBC diameter)
- connect arterial flow with venous return
- networks anastomose (connect) with each other in the parenchyma of an organ
- one layer of endothelium + BM, no tunica media or externa
- function: exchange of gases and metabolites
- number of capillaries varies with metabolic activity of tissue
221
precapillary sphincters
- smooth muscle, around metaareterioles
- control blood flow into capillaries: contract = shunt, relax = allow flow
222
control of precapillary sphincters
1) increase in NO, CO2 = relax
2) decrease in NO, CO2 = contract
3) SNS = vasoconstriction in most vessels (skin, GI tract), dilation in some vessels (skeletal muscle)
223
types of capillaries
1) continuous: most common
2) fenestrated
3) sinusoid
224
continuous capillaries
- continuous endothelial lining
- tight junctions and desmosomes
- continuous BM
- ex. brain, lungs
225
fenestrated capillaries
- pores (fenestrations) in endothelial cells allow for peptides and small proteins to pass through
- continuous BM
- ex. kidneys, intestines, most endocrine glands
226
sinusoidal capillaries
- large fenestrations
- thin or discontinuous BM
- allows passage of large solutes
- ex. liver, bone marrow, spleen
227
veins vs arteries
- 65-70% (~3.5L) of blood volume
- SNS = venoconstriction of smooth muscle (media), moves blood into arteriolar/capillary system
- generally have thinner walls and larger diameters than companion artery/arteriole (usually located together
228
(postcapillary) venules
- endothelium, BM, pericytes
- primary site of action of vasoactive agents (ex. histamine)
- site of extravasation of tissue fluid during inflammatory response
- can sometimes see lymphocytes passing through wall
- does not maintain shape in cross-section
229
veins
- structural changes from small to large not as distinct
- thin walls relative to diameter (low pressure)
- externa is the thickest
- no internal or external elastic laminae
- many contain valves (made from tunica intima)
230
skeletal muscle pump
- BP in veins too low to overcome gravity
- valves prevent backflow
- reliant on skeletal muscle contraction to move blood back to heart
231
common cause of edema
- chronic venous insufficiency (ex. compromised wall integrity = increased leakage)
- leads to excess interstitial fluid
232
lymphatic system functions
1) transports excess interstitial fluid
2) transports dietary lipids
3) carries out immunes responses
233
lymphatic organs
- primary: bone marrow, thymus
- secondary: lymph nodes, spleen, mucosa associated lymphoid tissue (MALT)
234
components of lymphatic system
1) lymph: interstitial fluid, lymphocytes, macrophages
2) lymphatic vessels: pass through lymphatic tissue and organs, deliver lymph to venous circulation
3) lymphatic tissues & organs: nodules, thymus, nodes, spleen
235
formation/flow of lymph
1) plasma in capillaries
2) interstitial fluid in interstitial spaces
3) lymph in lymphatic capillaries
4) lymphatic vessels
5) lymphatic ducts
6) junction of internal jugular and subclavian veins
- 3L/day fluid reabsorbed, excess becomes lymph
236
lymphatic capillaries
- close-ended tubes
- interspersed among blood capillary networks
- also have valves
- anchoring filament connects to surrounding CT, keeps capillaries open
- endothelium lacks tight junctions, has incomplete BM
237
lymphatic vessels
- similar to small veins
- valves closer together
238
lymphatic valves are created by...
overlapping endothelial cells
239
lymphatic trunks
- vessels merge to form trunks
1) jugular trunks (R/L): head + neck
2) subclavian trunks (R/L): upper limbs
3) bronchomediastinal trunks (R/L): chest
4) intestinal trunk: abdomen
5) lumbar trunks (R/L): lower limbs
240
lymphatic ducts
- trunks unite to form ducts
1) R. lymphatic duct: R. subclavian, jugular and mediastinal trunks --> empties into right venous angle
2) thoracic duct: L. subclavian, jugular, mediastinal trunks --> empties into left venous angle
- cisterna chyli: beginning part of thoracic duct, accepts from lumbar and intestinal trunks
241
lymphoid cells function
- respond to antigens to initiate (adaptive) immune response
- invading bacteria, viruses, abnormal body cells, foreign proteins
242
T lymphocytes
- recognize antigens on surface of APCs
- once activated, divide into:
1) cytotoxic T cells: cell-mediated immunity, directly kill cells by apoptosis
2) memory T cells: second exposure elicits more rapid and severe response
3) helper T cells: modulate immune response of T/B cells
243
B lymphocytes
- can recognize antigen directly
- need helper T cells to become activated
- divide into:
1) plasma cells: Ab production
2) memory B cells: second exposure elicits more rapid and severe response
244
antibody function
- bind antigen on subsequent exposure, mark for phagocytosis
245
differentiation and maturation of lymphatic cells
- all born in bone marrow from stem cells
1) B lymphocytes (15-30%): mature in bone marrow, humoral immunity
2) NK cells (5-10%): mature in bone marrow, non-specific immune surveillance and attack of abnormal cells
3) T lymphocytes (70-85%): mature in thymus, cell-mediated immunity
- initial formation of B/T does not require antigen, but for every antigen there should be a lymphocyte capable of recognizing it
246
what defines a lymphatic organ?
CT capsule
247
lymphatic nodules
- oval masses of lymphatic cells
- not an organ, no CT capsule
- scattered throughout lamina propria of mucous membranes in GI tract, urinary, reproductive and airways --> MALT
- mucosa often has crypts
- aggregations form tonsils
- function: filter and attack antigens
248
lamina propria
CT, VANs, lymphatics and lymphatic cells of mucous membrane (beneath epithelial cells)
249
germinal center
- pale center of lymphoid nodules
- contains activated, dividing B cells (migrate in)
- surrounded by T cells
250
thymus
- bilobed organ, posterior to sternum
- largest, most active in youth
- decrease in size/activity with age (atrophy, becomes fatty tissue)
- prenatally: multipotential lymphoid stem cells from bone marrow populate thymus
- function: induction of central tolerance (immunocompetence), preventing autoimmunity
251
thymus lobes
- right and left lobes surrounded by CT capsule
- trabeculae divide parenchyma into incomplete lobules
- arteries, nerves and efferent lymphatics in capsule/trabeculae
- each lobule has darker staining cortex and lighter staining medulla
252
thymic cortex
- numerous thymocytes (developing T cells) with darker staining nuclei
- epithelioreticular cells (instead of reticular tissue): larger cells, oval nuclei and eosinophilic cytoplasm
- macrophages
- T cells divide rapidly, migrate to medulla
- T cells that recognize self (most) are eliminated by apoptosis, phagocytosed by macrophages
253
blood thymus barrier
- protects developing thymocytes from exposure to circulating antigens
- three major components:
1) endothelial cells: line wall, joined by tight junctions, thick BM
2) CT space (occupied by macrophages)
3) epithelioreticular cells: tight junctions, thick BM
254
thymic medulla
- loosely packed mature T cells (5%) amongst epithelioreticular cells
- T cells larger, more cytoplasm, stain lighter
- key feature = thymic corpuscles: concentrically arranged epithelioreticular cells packed with keratin, unknown function
- mature T cells leave thymus via post-capillary venules and efferent lymphatic capillaries to go to secondary lymphatic tissue and organs
255
lymph nodes
- round structures along pathways of lymphatic vessels
- have CT capsule
- parenchyma organized into cortex and medulla, divided by capsule and trabeculae
- cortex: lymphatic nodules
- paracortex: T cells
- stroma has reticular fibers
256
flow of lymph through lymph nodes
1) afferent vessel (unique to lymph nodes)
2) network of:
- subcapsular and trabecular sinuses: macrophages
- medullary cords and sinuses: B cells, macrophages
3) hilius/hilium
4) efferent vessel (T/B cells also leave through here)
257
lymph nodes function
- clean lymph of antigens via macrophages
- process and present antigens to T cells (paracortex)
- reticular fibers slow migration of antigens and cells
258
lymph node cortex
- B cells form nodules
- Ag causes B cells to proliferate and differentiate (swelling)
259
lymph node paracortex
- no nodules
- has T cells
- has high endothelial venules: specialized post capillary vessels that activated T/B cells enter through
260
lymph node medulla
- medullary cords: B cells, plasma cells (from cortex), macrophages
- antibodies leave via efferent lymph vessel
261
spleen
- largest single mass of lymphatic tissue
- left upper quadrant of abdomen
- CT capsule
- VANs and lymphatics enter/exit from hilium
- only has efferent lymphatics
- functions: immune response to antigens in blood, phagocytose old RBCs, reservoir for RBCs and platelets
262
spleen organization
- parenchyma: red pulp and scattered islands of white pulp, no cortex/medulla
- stroma: reticular fibers
263
splenic artery
end artery, branches within trabeculae into white pulp
264
white pulp
- rich in B/T cells, macrophages
- initiate immune response to blood pathogens
- blood leaves circulation to enter red pulp
- contains periarteriolar lymphoid sheaths (PALS): dominated by T cells, surround central arterioles
- also has germinal center: proliferating B cells
- basophilic due to densely packed nuclei
265
red pulp
- splenic cords rich in RBCs, macrophages and splenic sinusoids
- removes old RBCs, recycles iron
- end arteries: open circulation
- eosinophilic due to predominance of RBCs
266
splenic vein
- cleaned blood passes through walls of splenic sinusoids to re-enter circulation
- leave spleen via splenic vein
267
distinct regions of skin
1) epidermis: stratified squamous keratinized epithelium, 4-5 layers
2) dermis: dense layer of interlacing collagen/elastic fibers (CT)
268
skin functions
1) protection from external environment
2) prevents water loss
3) regulates body temperature
4) excrete and absorb substances
5) vitamin D synthesis
6) coordinates immune response to pathogens
7) detect cutaneous sensations
269
epidermis
- avascular, receives nutrients from dermis via diffusion
- four types of cells
1) keratinocytes: specialized epithelial cells that produce keratin
2) dendritic (Langerhans) cells: APCs found in keratinized skin, mucous membranes, superficial lymph nodes
3) melanocytes: processes extend into stratum spinosum, produce melanin
4) merkel cells: mechanoreceptors for gentle touch, stimulate afferent nerve endings
270
layers of skin
1) stratum corneum
2) stratum lucidum (only in thick skin)
3) stratum granulosum
4) stratum spinosum
5) stratum basale
"Big Stinky Gorillas Like Corn"
271
melanocytes
- body in basale, projections into spinosum
- secrete melanosomes into spinosum, location where melanin forms and is transferred to keratinocytes
- melanin shields nuclei from UV radiation, protects underlying dermis
- melanin degraded over time by keratinocyte lysosomes
272
melanocytes and skin colour
- ratio of melanocytes to keratinocytes varies depending on body region
- ratio consistent between races, by rate of lysosomal degradation differs (fate differs)
- amount of melanin produced impacted by genetics and sunlight exposure
- melanin: reddish-yellow to brownish-black
- melanin minimally produced in thick skin
- freckles = accumulation of melanin
- albinism: absence of melanin
273
what else contributes to skin colour?
- carotene: orange-yellow
- hemoglobin: bright red when bound to O2
274
stratum basale
- single layer of cells attached to BM
- dominated by basal cells (stem cells)
- also have melanocytes
- mitotic division into keratinocytes that move into superficial layers
- keratinocytes produce keratins, assemble into intermediate filaments (desmosomes and hemidesmosomes)
275
stratum spinosum
- several cells thick
- each keratinocyte contains bundles of keratin intermediate filaments from one end to the other
- start to produce keratohyalin granules (intermediate filament-associated proteins) and lamellar granules (pro-barrier lipids)
- dendritic cells also present
276
why is stratum spinosum "spiny"?
- cytoskeletal elements and desmosomes remain intact after tissue processing
277
stratum granulosum
- few layers thick
- darkly staining protein granules with keratohyalin
- keratinization begins: keratohyalin associate with keratin intermediate filament bundles --> formation of larger proteins which fill keratinocytes
- lamellar granules exocytose lipid-rich contents into intercellular spaces in granulosum and corneum --> epidermal water barrier
- keratinocytes begin to die (nuclei and organelles disintegrate, moving further away from blood supply)
278
stratum lucidum
- only in thick skin
- flattened cells, densely packed with keratin, no organelles/nuclei
279
stratum corneum
- several layers of anucleate squamous cells filled with keratin
- thick plasma membrane coated with extracellular lipids (water barrier)
- keratinocytes shed as pH dependent enzymatic activity breaks down desmosomes
280
psoriasis
- accelerated cell turnover (8-10 days instead of 47days)
- thickness of skin increases
- rate of cell death reduced
- stratum corneum shed
281
dermal-epidermal interface
- created by epidermal ridges and dermal papillae
- ridges on palms and soles of feet increase surface area and promote friction for secure grip
282
dermis
- areolar CT with collagen and elastic fibers
- function: nourish skin and temperature regulation (blood vessels, nerves, sensory receptors)
- two layers separated by a distinct boundary:
1) papillary
2) reticular (deeper)
283
papillary layer of dermis
- areolar CT
- VANs, lymphatics, sensory receptors (subpapillary plexus)
284
reticular layer of dermis
- thick collagen type 1
- coarser elastic fibers
- VANs (cutaneous plexus), lymphatics, sensory receptors
- hair follicles and glands
285
temperature regulation in dermis
- arteriovenous anastomoses in cutaneous plexus control blood flow into subpapillary plexus
- cold weather: limit flow to limit loss of body heat
- hot: opposite
286
hypodermis
- areolar CT + lots of adipocytes
- not considered part of skin
- function: anchors skin to underlying structures
- aka subcutaneous layer or superficial fascia
287
degrees of burn
1) epidermis only
2) epi + dermis
3) epi + dermis + hypo
288
appendages of skin
- derived from invagination of epidermal epithelium during development
1) hair follicles (hair)
2) nail beds (nails)
3) sebaceous (oil) glands
4) sweat glands
289
hair structure
- keratinized cells that develop from hair follicles
- hair shaft: exposed part
- surrounded by CT sheath
- arrector pili attach to sheath
- hair bulb containing germinative cells
- associated with sebaceous glands
- nourished by dermal papilla
290
arrector pili
- smooth muscle
- thermoregulation
- contraction = hair stands up
291
follicular bulge
- usually below arrector pili
- contains epidermal stem cells
292
hair matrix
- epithelial cells that produce hair
- containing basal cells, melanocytes
- stem cells from follicular bulge move down and populate the hair bulb
293
sebaceous (oil) glands
- type of sweat gland located over entire body except palms and soles of feet
- typically connected to hair follicles
- simple branched alveolar
- secrete sebum: waxy oily lipid
- holocrine secretion
- function: prevent dehydration of hair, skin + prevent bacterial growth
294
sweat glands
- secretory unit in hypodermis
- duct in dermis and epidermis
- secrete fluid by merocrine secretion
- simple coiled tubular
- two types: apocrine and eccrine
295
apocrine glands
- become active at puberty
- limited to axillae (armpits), areolae, perineal (genital/rectal) region
- associated with hair follices
- secretion is protein rich and contains pheromones, reacts with bacteria to create body odour
296
eccrine glands
- distributed all over the body
- secretion is 99% water + electrolytes
- temperature regulation
297
innervation of sweat glands
- SNS
- myoepithelial cells are innervated, responsible for contractions and discharge of secretions
298
eccrine vs apocrine on micrograph
- eccrine smaller, narrower lumen with darker stained cells
299
breast tissue
- shape and volume mostly subcutaneous fat (adipose tissue), except during pregnancy (large sebaceous glands)
- parenchyma derived from epithelia, supported by CT stroma
300
mammary glands
- no function in males
- develop further at puberty under hormonal influence
- modified apocrine sweat glands that produce milk
- compound alveolar glands
301
mammary gland structure
- pectoral fascia (CT)
- suspensory ligaments (not muscle-bone) attach breast to dermis
- pectoral fat
- lobules containing alveoli connected by lactiferous ducts
- lactiferous ducts connect to form lactiferous sinus (enlarged area where milk accumulates)
302
breast lymphatic drainage
- most lymph drains to axillary lymph node --> subclavian trunk
- some drains to parasternal nodes --> bronchomediastinal trunk
