Download Tissues and Integument

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Tissues
Introduction
1. Science that studies the structure of an organism is anatomy
a. Anas = to cut
b. Tomos = apart
2. Science that studies how a particular structure functions is physiology
3. Levels of structural organization
a. Atoms
b. Molecules
c. Organic macromolecules
1) Carbohydrates
2) Lipids
3) Proteins
4) Nucleic acids
d. Cells
1) Composed of organelles like: nucleus, mitochondria, endoplasmic
reticulum (ER), Golgi body, lysosomes, etc
2) Plasma membrane-a phospholipid bilayer with embedded proteins
3) Basic understanding of cell internal structure and physiology is
required for success in Bio 201-Bio 156 is a strongly recommended
prerequisite
e. Cells are united into tissues; a group of cells with similar structure, but
grouped to perform a common function(s)
1) 4 general categories of tissues: epithelial, connective, muscle,
nervous
f. Tissues are united into organs; a group of 2 or more tissues with discrete
boundaries and have a more generalized function(s) than a tissue
1) Examples: liver, spleen, gall bladder, esophagus, stomach, small
intestine, heart, lungs, brain, etc.
g. Organs are often organized into organ systems; groups of organs
performing a common function
1) Bio 201
a) Integumentary system
b) Skeletal system
c) Muscle system
d) Nervous system
2) Bio 202
a) Endocrine system
b) Cardiovascular (circulatory) system
c) Digestive system
d) Respiratory system
e) Urinary (excretory) system
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f) Reproductive system
h. All organ systems combine to make up the organism
4. Assigned reading in text:
a. Anatomical planes
b. Directional terms
c. Body cavities
5. General kinds of tissues
a. A tissue is a group of cells with similar structure, but grouped to perform
a specific function(s)
b. 4 general kinds of tissues are:
1) Epithelial (covered in exam I)
2) Connective (covered in exam I)
3) Muscle (covered in exam 3)
4) Nervous (covered in exam 4)
Epithelial Tissues
1. Basic locations:
a. As outer coverings of an organism.
1) Ex: epidermis of skin
b. As linings of tubes, canals, vessels, etc.
1) Ex: lining of GI tract, ureter, bladder, and endothelium of a blood
vessel
c. As outer coverings of internal organs
1) Ex: mesothelium layer over organs
2. Basic functions: protection, secretion, & absorption
3. Characteristics:
a. Cellularity-tissue is composed almost entirely of cells with very little
acellular substance called the matrix
b. Diverse kinds of specialized contacts: desmosomes, tight jcts, & gap jcts
1) Desmosomes-proteins that hold cells together
2) Tight jcts-proteins connecting two cells that prevent
substances/organisms from going between cells
3) Gap jcts-protein portals that join two cells and allow transport of
small molecules between cells
c. Polarity-one border of tissue faces the lumen/outside while other border
contacts a basement membrane
d. All epithelial tissues contact a basement membrane
1) Basement membrane composed of two sublayers:
a) Nonliving, acellular, adhesive material made from
glycoproteins and fine protein filaments; secreted by cells of
epithelial layer-basal lamina
b) A nonliving, acellular, material composed of collagen and
reticular fibers; secreted by cells of connective tissue-reticular
lamina
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c) Basement membrane = basal lamina + reticular lamina
e. Avascularity-without a blood supply or blood vessels
1) W/o blood vessels, epithelial tissues have to acquire
nutrients/oxygen via diffusion from blood vessels in CT
f. High capacity to regenerate
1) With outer locations, epithelial tissues are subjected to much wear
and tear; to replenish damaged/lost cells they rapidly divide
4. Classification
a. Cell arrangement:
1) Single layer of cells = simple
2) More than one layer of cells = stratified
b. For any stratified tissue, the shape of cells in outer layers determines
shape classification
5. Survey of different kinds:
a. Simple squamous epithelium
1) Description: a single layer of squamous-shaped cells
2) Side view: fried egg
3) Top view: tile floor
4) Functions: thinness enhances diffusion process; also secretion
5) Examples:
a) Simple squamous epithelium in alveoli of lungs
b) Simple squamous epithelium that lines blood vessels (&
heart) is called endothelium
c) Simple squamous epithelium that covers internal organs &
lines body cavities is called mesothelium (serous membranes)
b. Simple cuboidal epithelium
1) Description: a single layer of cuboidally-shaped cells; nuclei are
rounded & well-centered
2) Descriptive phrase: string of beads
3) Functions: secretion & absorption
4) Examples:
a) Thyroid gland follicles
b) Most tubules in kidney
c. Simple columnar epithelium
1) Description: a single layer of columnarly-shaped cells; nuclei are
oval and off center (nucleus more in bottom/basal half of cell)
2) Descriptive phrase: row of soldiers
3) Functions: secretion, absorption, protection, movement
4) Modifications:
a) Nonciliated
i. Mucus-secreting cells called goblet cells
ii. Cells, called brush border cells, with foldings of plasma
membrane called microvilli
b) Ciliated
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i. Possess cilia on luminal (apical) surface
5) Locations:
a) Fallopian tubes in female reproductive tract
b) Small & large intestine with goblet & brush border cells
d. Pseudostratified (columnar) epithelium
1) Description: Mostly a single layer of cells, taller than wide, but of
different heights; ‘all’ cells touch basement membrane
2) Tissue looks stratified based on different levels of nuclei, but has
thickness of a simple epithelial tissue
3) Ciliated and nonciliated (goblet cells) forms
4) Functions: secretion, protection, movement
5) Locations:
a) Most of respiratory tract-trachea
e. Stratified squamous epithelia:
1) Description: multiple layers of squamous-shaped cells; cells of
deepest layers may be irregular, cuboidal, or columnar in shape
2) Function: Found in areas subjected to heavy wear and tear
(protection)
3) Modifications:
a) Nonkeratinized-outer cell layers alive and metabolic
b) Keratinized-outer cell layers dead-nonmetabolic
4) Locations:
a) Nonkeratinized: Linings of oral cavity, esophagus, vagina,
and anal canal
b) Keratinized: Epidermis of skin
c) Look for exfoliation feature to identify
f. Stratified cuboidal epithelial:
1) Description: multiple layers (usually only two) of cuboidally-shaped
cells
2) Function: secretion and protection
3) Locations:
a) Ducts of sweat glands and other large glands (testes and
mammary)
g. Stratified columnar epithelia:
1) Description: multiple layers of mostly irregularly-shaped cells; cells
at surface are taller than wide
2) Rarest of epithelial tissues
3) Function: protection
4) Location: found in transition zones between other epithelial tissues
h. Transitional epithelia:
1) Description: cells of basal layer are cuboidal or columnar; surface
cell shape varies from squamous to rounded with distention or organ
2) Function: protection in helping resist osmosis
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3) Locations: linings of urinary bladder, ureter, urethra, and renal
pelvis (in kidney)
Connective Tissues
1. Most abundant and widely distributed tissue in the body
2. Basic functions: binding (connects), supports, protection, insulation, and
transport
3. Characteristics:
a. Common origin from embryonic tissue called mesenchyme; a tissue
derived from the embryonic germ tissue mesoderm
1) Sperm fertilizes egg forming zygote
2) Zygote divides (undergoes cleavages) forming 2, 4, 8, & 16 cell
stages
3) From ~ 16-32 cells a solid ball of cells forms
4) Next divisions hollow out center forming a hollow ball of cells
5) From this hollow ball of cells, one end cell divisions start
invagination (pushing inward) creating early gut
6) At this point 3 germ tissues, genetically committed tissues, are
recognized:
a) Ectoderm-outer cells of this early embryo giving rise to
epidermis and nervous system
b) Mesoderm-cells that briefly fill body cavity and give rise to all
connective tissues (CT), muscle, and parts of various organs
c) Endoderm-cells that line early gut and give rise to gut lining,
part or all of digestive organs, and other various organs
b. Have a large amount of acellular substance called the matrix; cells are
often widely spaced and not in direct contact
4. CT-Basic structural features
a. Ground substance
1) Unstructured material that fills space between cells and houses
fibers
2) Composed of water, electrolytes, and a unique group of
proteoglycans, glycoproteins, and GAGs
a) Proteoglycan-large bottlebrush-shaped molecule
b) Glycosaminoglycans-sulfanated carbohydrate-protein
i. hyaluronic acid
ii. chondroitin sulfate
3) Gives ground substance consistency of colorless maple
syrup
3) A medium for diffusion of oxygen and nutrients, but also slows
bacteria making them easier for immune cells to catch
b. Fibers-proteins found in ground substance giving each kind of CT a
unique character depending upon combination
1) Collagen fibers called white fibers
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a) Tough, resist stretch, but some flexibility
b) Often appear ‘wavy’ under microscope
c) Examples: tendons, ligaments, and dermis of skin
2) Reticular fibers are thin collagen fibers coated with glycoprotein
a) Form framework for spleen & lymph nodes
b) Branch and rejoin-reticulate
3) Elastic fibers called yellow fibers
a) Thin branching fibers made of elastin
b) Stretch & recoil like rubber band (elasticity)
c) Very dark under light microscope
d) Give skin, lungs, & arteries ability to stretch & recoil
4) Ground substance + fibers = Matrix
c. Cells
1) Often exist in active and less active states denoted by:
a) blast-actively secretes new matrix; can be mitotic
b) cyte-maintains matrix; usually nonmitotic
2) Cells types associated with CT groups:
a) Connective tissue proper-fibroblast or fibrocyte
b) Cartilage-chondrocyte or chondroblast
c) Bone-osteocyte or osteoblast
d) Blood-hemocytoblast
3) CT proper cell types:
a) Fibroblasts produce fibers & ground substance
b) Macrophages=large cells that wander through CT
phagocytizing foreign material & activating immune system
(arise from monocytes a kind of white blood cell)
c) Neutrophils-WBC that wander in search of bacteria
d) Plasma cells-synthesize antibodies arise from WBC’s
e) Mast cells-secrete heparin that inhibits clotting and histamine
that dilates blood vessels
f) Adipocytes-fat cells that store fat
5. CT Proper survey
a. Loose division has fibers widely spaced with examples being: loose
areolar, adipose, and reticular
b. Dense division has fibers densely packed with examples being: dense
regular, elastic, and dense irregular
c. Loose division
1) Loose areolar CT
a) Description: a semifluid ground substance of mostly
hyaluronic acid; fibers and cells dispersed; cells diverse
b) Functions:
i. Provides reservoir for water & salts for surrounding
tissues
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ii. Packaging material between organs such as muscles,
around glands and blood vessels; also subcutaneous
(hypodermis) tissue
2) Adipose
a) Description: a modified areolar CT with large numbers of
adipocytes
i. Phrase: “chicken wire” appearance
ii. Little matrix and richly vascular
b) Functions:
i. Storehouse of nutrients and E
ii. Shock absorber; cushioning for organs
iii. Insulation
3) Reticular CT
a) Description: Loosely interwoven reticular fibers with many
reticulocytes and lymphocytes (a kind of WBC)
b) Forms ‘stroma’ of various organs: lymph nodes, spleen, liver,
bone marrow
c) What is the stroma of an organ?
i. The organ, liver, is made up of liver cells; the substance
that holds these cells together and gives the liver its
unique shape is reticular CT or the stroma
d. Dense division
1) Dense regular CT
a) Description: collagen fibers are densely packed and are
arranged parallel to each other; fibroblasts are squeezed
between fibers
b) Functions: minimal stretch, but great strength in direction of
fibers
c) Locations:
i. Tendons-connect muscle to bone
ii. Ligaments-connect bone to bone
2) Elastic CT
a) A dense regular CT with a high per cent of elastin fibers; also
known as yellow tissue because of color
i. Fibroblasts are larger and have bigger nuclei
ii. Tissue has a dark look to it
b) Functions: allows expansion of an organ with return to
original size or length
c) Locations:
i. Ligaments of vertebral column
ii. Vocal cords
iii. Walls of medium to large arteries
3) Dense irregular CT
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a) Description: densely packed collagen fibers running in many
directions; scanty open space; few visible cells
b) Withstands stresses applied in different directions
c) About 80% of dermis in skin; capsules around organs (liver,
kidney, spleen), periosteal layer of bone where tendons and
ligaments insert
6. Cartilage-covered in exam 2 under skeletal system
7. Bone- covered in exam 2 under skeletal system
8. Blood-covered in Bio 202 under circulatory system
9. Diseases
a. Deficiences in collagen & elastin cause serious problems
b. Marfan’s syndrome = hereditary defect in fibrillin that stabilizes elastic
fibers
1) Tall stature, long limbs, spinal curvature & weakening of heart
valves & arterial walls (rupture of aorta)
Integumentary System
1. Largest organ of the body (15% of body weight at about 9 lbs)
a. SA = 1-2 m2
b. Every square inch of skin houses: 12 ft of nerves, 15 feet of blood
vessels, and over a million cells
c. Normal thickness of 1-2 mm, up to 6 mm
d. Thicker skin (palms & soles) has thicker stratum corneum, no hair
follicles or sebaceous glands
2. Two layers:
a. Epidermis
1) Stratified squamous epithelium
2) Can contain 5 layers or strata
b. Dermis
1) Connective tissue
c. Scientific study and medical treatment of the integument is called
dermatology
3. Functions:
a. Protects us from bacterial invasion and mechanical and chemical injuries
b. Prevents heat & water loss
c. Eliminates wastes such as: urea, salts, lactic acid, and ammonia
d. Vitamin D synthesis
e. Houses receptors for cutaneous sensation
f. Acts as a reservoir for blood
4. Cell types and layers (strata) of epidermis
a. Keratinocytes
1) Main cell type
2) Shape varies from cuboidal in lower strata to squamous in mid to
upper strata
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3) Mitotic in stratum basale and spinosum-source of new
keratinocytes
4) Synthesize keratin in mid layers
5) By the time these cells are pushed up into the stratum corneum,
they are little more than plasma membranes packed with keratin; they
are dead and are exfoliated
6) Function: protection
b. Stratum basale
1) Single layer of cuboidal or low columnar cells sitting on basement
membrane
2) Cell types in this layer
a) Keratinocytes
i. Undergoes mitosis to replace epidermis
ii. Most common cell type
b) Melanocytes synthesize protein melanin
i. Distribute melanin into & from cell processes
ii. Melanin is picked up by keratinocytes via phagocytosis
and used to shade their nuclei form UV radiation
c) Merkel’s cells are touch receptors associated with nerve
fibers from a Merkel disc
c. Stratum spinosum
1) Several layers of keratinocytes thick
2) Appear spiny due to shrinkage during histological preparation
3) Contains dendritic (Langerhans) cells
a) Macrophages from bone marrow that migrate to epidermis
b) 800 cells/mm2
c) help protect body against pathogens by presenting them to
the immune system
4) Stratum basale + s. spinosum = s. germinativum
d. S. granulosum
1) 3 to 5 layers of flat keratinocytes
2) Contain keratinohyalin granules-intermediate filaments convert
granules to keratin
3) Produce lipid-filled vesicles that release a glycolipid by exocytosis
to waterproof the skin
a) Forms a barrier between surface cells and deeper layers of
epidermis
b) Cuts off surface strata from nutrient supply and cells above
die
e. S. lucidum
1) Thin translucent zone seen only in thick skin (palms/soles)
2) Keratinocytes are packed with eleidin, a precursor to keratin
a) Eleidin does not stain well
3) Cells have no nucleus or organelles
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f. S. corneum
1) Up to 30 layers of dead, scaly, keratinized cells
2) Surface cells flake off or exfoliate
3) Keratinocytes are little more than plasma membranes packed with
keratin
5. Dermis
a. Thickness = 0.6 – 3 mm
b. Composition
1) Collagen, elastic & reticular fibers, fibroblasts & accessory
structures such as hair follicles, blood vessels, lymphatic vessels,
nerve endings, receptors, and glands
2) Dermal papillae are upward extensions of the dermis into the
epidermis forming the ridges of the fingerprints
3) Commonly referred to as the hide of the animal
4) Layers:
a) Papillary layer is loose areolar & dermal papillae of upper
20% of the dermis
b) Reticular layer (dense irregular CT) is deeper part of dermis
c. Papillary layer
1) Loose areolar CT
2) Dermal papillae house capillaries, nerve endings, & receptors
3) Fingerprints (friction ridges) created by papillae to improve grip on
smooth surfaces
4) ~ 20% of dermis
d. Reticular layer
1) Dense irregular CT
2) Collagen fibers retain water and elastic fibers give skin flexibility
3) ~ 80% of dermis
6. Hypodermis
a. Also known as subcutaneous tissue or superficial fascia
b. Has more adipose than dermis
c. Functions:
1) E reservoir
2) Thermal insulation
d. Hypodermic injections into highly vascular adipose tissue
7. Skin colors (Pigmentation)
a. Hemoglobin is red pigment of red blood cells (RBCs) and visible through
dermal collagen fibers
b. Carotene is yellow pigment of vegetables & egg yolks; concentrates in s.
corneum and subcutaneous fat
c. Melanin pigment produced by melanocytes
1) Pigment synthesis stimulated by UV radiation from sunlight
2) Produces yellow, brown, black, & reddish hues
d. Abnormal skin colors
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1) Cyanosis is blueness resulting from deficiency of oxygen in the
circulating blood (cold weather)
2) Erythema is redness due to dilated cutaneous vessels (anger,
sunburn, embarassment)
3) Jaundice is yellowing of skin & sclera due to excess of bilirubin in
blood (liver disease)
4) Bronzing is golden-brown color of Addison disease (deficiency of
glucocorticoid hormone)
5) Pallor is pale color from lack of blood flow
6) Albinism is a genetic lack of melanin
7) Hematoma is a bruise (visible clotted blood)
8. Skin Markings
a. Hemangiomas (birthmarks)
1) Discolored skin caused by benign tumors of dermal blood
capillaries (strawberry birthmarks disappear in childhood; port wine
birthmarks last for life)
b. Freckles & moles = aggregations of melanocytes; freckles are flat, moles
are elevated
c. Friction ridges leave oily fingerprints on touched surfaces; unique pattern
formed during fetal development
d. Fkexion creases form after birth by repeated closing of hand
e. Flexion lines form in wrist & elbow areas
9. Hair
a. Functions:
1) Body hair too thin to provide warmth
2) Sensory functions alerting us to parasites crawling on skin
3) Scalp hair provides heat retention & sunburn cover
4) Sex and individual recognition
5) Beard, pubic, & axillary hair indicate sexual maturity & help
distribute sexual scents
6) Guard hairs & eyelashes prevent foreign objects from getting into
nostrils, ear canals, and eyes
7) Expression of emotions with eyebrows
b. Characteristics
1) S. corneum of the skin is composed of soft pliable keratin
2) Hair & nails are composed of hard keratin
a) Toughened by disulfide bridges between molecules
3) Hair found almost everywhere on the body
a) Differences between sexes or individuals is really difference
in texture and color of hair
c. Structure of hair & follicle
1) Hair is filament of stratified squamous keratinized cells
2) Shaft is visible above skin; root is below and within follicle
3) In cross section (cs): medulla, cortex, & cuticle layers
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4) Hair follicle is oblique tube within the skin
a) Bulb is swelling in base where hair originates
b) Vascular tissue (papilla) in bulb provides nutrients
c) Cells lining the follicle interlock with scales of cuticle to resist
pulling on the hair
5) Texture & cross-sectional shape of hair
a) Straight hair is round, wavy is oval, and kinky is flat in cs
6) Hair color is mostly due to melanin pigment
7) Epithelial root sheath is an extension of the epidermis (lies next to
root)
8) Connective tissue root sheath is derived from the dermis
(surrounds it)
9) Hair receptors entwine each follicle and arrector pili muscle
attaches to outer surface
d. Causes of different hair colors
1) Brunette is due to heavy melanin pigmentation
2) Blond is due to scanty amount of melanin
3) Red hair is colored by the iron-containing pigment trichosiderin
4) White hair is due to air in medulla & lack of pigment in color.
5) Gray hair is a mixture of white and pigmented hairs
e. Growth of hair
1) Mitosis in s. basale of epithelial root sheath; cells become
keratinized as they are pushed upward
2) Grows 1 mm every 3 days for 2 to 4 yrs
3) Dormant phase last 3-4 months
4) As new hair begins to grow, it pushes out old hair
5) Eyelashes & eyebrows only grow for 3 to 4 months
10. Nails
a. Clear, hard derivative of s.corneum where cells are densely packed and
filled with hard keratin
b. Flat nails allow for fleshy, sensitive fingertips
c. Growth rate is 1 mm per wk
1) News cells added by mitosis in the nail matrix
2) Growth zone at proximal edge of nail
3) Nail plate is visible part of nail
11. Glands
a. Merocrine Sweat Glands
1) Also called eccrine
2) Most common
3) Abundant on palms, soles, & forehead
4) Secretion by exocytosis
5) Duct coils to surface and sweat exits via pore
6) Sweat is:
a) 99% water
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b) urea, NaCl, uric acid, ammonia, lactic acid, vitamin C, &
antibodies
7) Function: thermoregulation where 500 ml of insensible perspiration
occurs each day
b. Apocrine sweat glands
1) Axillary, anogenital, areolas around nipples, & beard area
2) Secretion is by exocytosis
3) Duct coils to hair follicle and sweat exits along pore next to root
4) Similar composition to merocrine, but has fatty acids & proteins
that give it a milky appearance
5) May be equivalent to sexual scent glands of other mammals
6) Bacterial action on urea can lead to body odor
c. Sebaceous glands
1) Holocrine-oily secretion called sebum is not by exocytosis, but by
broken down cells oozing along hair root & shaft
a) Lanolin in skin cream is sheep sebum
2) Flask-shaped gland with duct that opens into hair follicle-secretion
is by cell rupture
3) Sebum composition: mixture of triglycerides, cholesterol, proteins,
and electrolytes
4) Important as a skin & hair lubricant, but also has antibacterial
properties
d. Breasts & mammary glands
1) Breasts of both sexes rarely contain glands
2) Secondary sexual characteristic of females
3) Mammary glandular tissue found only during lactation and
pregnancy
a) Modified apocrine sweat gland
b) Thicker secretion released by ducts at nipple
4) Mammary ridges or milk lines
a) 2 rows of mammary glands in most mammals
b) Most milk from anteriormost glandular tissue in row
c) Primates (apes, monkeys, humans) kept only anteriomost
glands
12. Skin diseases
a. Most vulnerable organ to injury & disease; most common in old age
b. Skin cancer
1) Induced by UV rays of sun
2) Most common in fair-skinned and elderly
3) 3 types: basal cell carcinoma, squamous cell carcinoma, malignant
melanoma
4) Basal cell carcinoma
a) Arises from cells of the s. basale & eventually invades dermis
b) Treated by surgical removal, freezing, & radiation
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5) Squamous cell carcinoma
a) Arises from keratinocytes in the s. spinosum
b) If neglected, metastasis to lymph nodes can be lethal
6) Malignant melanoma
a) Most deadly cancer
b) Arises from melanocytes of a preexisting mole
c) ABCD = asymmetry, border irregular, color mixed, & diameter
over 6 mm
c. UVA, UVB, & sunscreens
1) UVA are tanning rays, but can also burn
2) UVB are burning rays, but also tan
3) Both thought to initiate cancer
4) As sale of sunscreens has increased so has skin cancer
a) Those who use have higher incidence of basal cell carcinoma
b) Chemical (PABA, zinc oxide, titanium oxide) in sunscreen
damages DNA & generates harmful free radicals