Lecture 3 - Histology: study of tissue Flashcards
What is tissue
-group of cells having similar structure & identical or similar functions
What are the 4 classification types of tissues
- epithelial
- connective
- nervous
- muscle
What is epithelial tissue
- sheet of cells that covers an external or internal surface
- epithelium is typically at the interface btw 2 regions & the substances that are either released or absorbed must pass through it
What is histology
Study of tissue
What are the 2 forms of epithelial tissue
- Covering and lining epithelium
2. glandular epithelium
Where is the covering and lining epithelium 4
- external layer of skin (epidermis)
- lines open cavities of resp & digestive system (forms mucosa w/ ct)
- cavities of the heart & internal wall of blood vessels (endothelium)
- covers the internal organs (forms the 3 serosa w/ ct - peritoneum, pleura, pericardium)
Where is the glandular epithelium
- cells that secrete particular products
- can be endocrine (secrete hormones, rich in hormonal receptors)
- can be exocrine ( secrete various products, mucus, Bile, enzymes)
What is the function of epithelial tissue
Protection, absorption, sensory reception, excretion, secretion, filtration
What are the 3 types of cellular junction (what joins cells tgthr)
- Tight junctions
- Desmosomes
- Gap junctions
What is structure of tight junctions
- form impenetrable (water tight) link btw cells (like zipper)
- involves adjacent plasmic membranes proteins
What is the function of tight junctions
- stops molecules from getting btw adjacent cells
- usually in epithelial cells of digestive system
- > stoos digestive enzymes and micro organisms from passing into blood
What is the structure of Desmosomes
Anchoring junctions
- button (plaque) that causes pressure
- proteins (cadherins) inbetween cells joins 2 plaques
- intermediate filament (keratin) attach 1 plaque to another
What is the function of Desmosomes
- joins adjacent cells and stops from separating
- prevents tearing when stretching occurs
- many found where mechanical forces are sizable like skin, cardiac muscle, cervix
What is the structure of gap junctions
- cells come closer without touching
- connexions (tubular proteins ) forms channel called connexion that crosses the 2 cells membranes
What is function of gap junctions
-allows cells to communicate and coordinate activities more freely
allows exchange of small hydrophilic molecules from 1 cell to another (heart smooth muscle)
What are the 2 surfaces of epithelial tissue
- apical
2. Basal
What is the apical surface and its characteristics
“Free” surface
- facing exterior or at internal cavity
- smooth
- have microvili (when very dense = brush border)
- covered w/ cilia (especially mucosa of resp airways and uterine tubes)
What is basal membrane and its characteristics
Attached to underlying CT that supports them
- epithelial all rest on CT
- > basal membrane joins the 2
- a cellular structure
- 2 components: basal and reticular laminae
What is basal lamina and its function
- made of glycopeoteins secreted by epithelial cells
- selective filter that decides which molecules will diffuse up to epithelial cells
- cells use it to migrate when tissue needs repair
What is reticular laminae and it’s function
- fine network of collagen fibers secreted by CT
Function: - support and reinforcement
-represents limit epithelial cell should not multiply beyond (cancer disobeys this)
Where do epithelia get their requirements
They are innervated but avascular
- have neurofibers (sensory receptors)
- have NO blood vessels
- get requirements by diffusion of nutrients from CT
How does epithelial tissue regenerate
High capacity of reproduction via mitosis
What are the 2 factors that classify epithelial tissue
- Number of layers
2. Shape
What are the 3 classifications of layer for epithelial tissue
- simple
- stratified
- transitional
What are the 4 shape classifications
- squamous( flat)
- cuboidal
- columnar
- pseudocolumnar
What is function of simple squamous
- diffusion (pulmonary aveoli)
- filtration (renal glomerular capsules)
- osmosis
- favors diffusion of nutrients and waste
What are two specialized names that inform of simple squamous locations
- endolthelium: lines interior of heart, blood & lymphatic vessels and constitutes capillaries
- mesothelium: forms the epithelial layer of serosa
Function of simple cuboidal epithelial cells
- secretion (mucus, sweat, digestives, enzymes)
- absorption (surface of ovaries germinal epithelium,pigmented epithelium of the retina, renal tubes)
Function of simple columnar epithelium
- absorption & secretion roles
- ciliated or not
- can have microvili
- can have goblet cells (apical part filled with mucin)
- mucus that is secreted lubricates & protects (digestive tract from the stomach to the anus )
- ciliated & goblet cells (respiratory airways), cilia transport mucus & foreign bodies out of the body
What is pseudostratified columnar
Odd structure ( stratified appearance but just 1 layer of column type cells)
- all cells attached to basal membrane
- may be ciliated like upper resp tract
- secretion and absorption
- ducts of many glands, male urethra, pharyngo-tympanic tubes (auditory/ eustachian)
What is stratified squamous
- in areas of wearing down so involves protection
- regenerate from bottom to top
- types are determined only by the superficial cells
- impermeable enough & resistant to wearing down
- basal cells reproduce and head to surface as age loosing blood irrigation dehydrating, hardening and detaching
- can be keratinized (skin)
- or not ( epidermis that enters in a short distance)
Where would you find stratified cuboidal
- rare, protection
- ducts: mammary, sweat, salivary glands
Where would you find stratified columnar
- rare, protection
- urethra (male)
What is the function of transitional epithelium
- lines organs of urinary sys
- allows a tissue to extend w/o ripping
- in relaxed state (cuboidal)
- in tense state (squamous)
What is the function of gladular epithelium
- secretory tissuee of glands
- glands produce secretions that are generally proteins in solution
- these proteins are synthesized, transformed by golgi complex & gathered in secretory vesicles near the apical surface of epithelium
- Glandular epithelium is found in the deep layer of the covering and lining epithelium
- Glands are made of 1 or many cells specialized in secreting
Where are 3 places glandular epithelium release secretions
- in ducts
- on the surface (skin or cavity)
- in blood
What are the 2 categories of glandular epithelium
- endocrine
2. exocrine
What is the function of endocrine glands
- forms the endocrine system
- lacking ducts
- secretions (only hormones) go into the extracellular liquid & end up in the blood
Functions of exocrine glands
- secretes (mucus, sweat, oils, waxes, digestive enzymes, milk) into ducts
- secretes onto surface of skin or into lumen of a hollow organ
Characteristics of unicellular exocrine glands
-all produce mucin (ex. goblet cells)
Characteristics of multicellular exocrine glands
- subdivides into simple and compound glands according to the duct present: either simple or ramified
- also divide into tubular & alveolar glands according to the form of the secretory segment of the gland
What is the odd-ball mode of secretion holocrine
-accumulate secretion in the cell which dies & releases its contents ( ex. sebaceous glands)
What is the odd-ball mode of secretion Merocrine
-releases secretions via exocytosis at the apical pole; the majority of glands (ex. salivary glands, pancreas, most sweat glands)
What is the odd-ball mode of secretion Apocrine
-secretion accumulate at the apical surface of the cell (storage) that detaches (ex.mammary glands)
What are 6 functions of connective tissue (C.T.)
- support
- protection
- insulation
- making compartments
- transport
- storage of energy
What is the structure of connective tissue
- cells + matrix (ground substance) + fibers
- Matrix can be liquid, semi-liquid, gelatinous, fibrous or calcified
- innervated
- irrigated by blood
- > except cartilage: tendons are poorly irrigated, thus their repair is slow
What is the immature type of C.T. cell and what does it do
- blasts
- divide via mitosis to produce the matrix specific to the C.T.
ex. fibroblast, hemocytoblast, chondroblast, osteoblast
What do you call a mature C.T. cell
- cyte
ex. adipocyte, leukocyte, mastocyte
What are physical characteristics of C.T.
- ground substance contains extracellular liquid & molecules such as proteoglycans (core protein) with glycosaminoglycanes attached to it
- ex. chondroitin sulfate, keratan sulfate, hyaluronic acid)
- these substances form gels + or - hydrated
What are the 3 types of loose C.T.
- Areolar
- Adipose
- Reticular
Where is Areolar C.T. (loose C.T.)
cell: fibroblast, macrophages, plasmocyte, WBC, adipocyte, mastocyte
- subcutaneous tissue, around small blood vessels, nerves, cover glands, lamina propria of mucosa
Where is adipose tissue (loose C.t.)
- Everywhere you find areolar C.T.
- White fat: cell has 1 large fat droplet, high metabolic activity, highly vascularised, does not undergo division 22% male, 15 % female
- Brown fat: cell has many small droplets & many mitochondria, important in thermogenesis (babies have alot)
Where do you find Reticular C.T.
- fibers filter the extracellular fluids & support WBC (especially lymphocytes) that phagocytized unwanted substances
- forms the stroma of flexible (loose) organs (liver, spleen, lymphatic nodes)
What are 3 types of Dense C.T.
- regular
- irregular
- elastic
Where is regular dense C.T.
- poor irrigation, resistant to tension, allow a bit of stretching
- tendons (bone-muscle), ligaments (bone-bone)
Where is irregular dense C.T.
- resistant to multidirection tension
- Deep dermis; capsules, organ capsules (testicles, kidney, bone, cartilage, muscles, nerves)
Where is elastic C.T.
- Allow stretching
- walls of arteries
Physical characteristics: cartilage
- Chondrocytes in lacuna (frm chondroblasts); not irrigated, not innervated (healing is slow)
- Covered by the perichondrium (vascularized, dense irregular C.T. with exception fibrous)
What are the 3 types of cartilage
Hyaline
Elastic
Fibrous
What is Hyaline cartilage
- collagen (delicate) most abundant
- covers the end of the bone, reduces friction of articulations, absorbs shocks
- nose, trachea, bronchus
What is elastic cartilage
- elastic fiber (abundant)
- allow flexibility, maintain shape
- ear pinna, epiglottis, auditory tube
What is fibrous cartilage
- Collagen (large, strong, rigid)
- absorbs shocks
- intervertebral discs, knee meniscus, under the point of attachment of tendons, pubic symphysis
What are 2 types of bone
compact
spongy
Characteristics of bone
- collage
- matrix hard bcs of calcium salt deposits in layers
- highly vascularized, site of hematopoiesis, re bone marrow fills the holes btw the trabeculae
- sound in skeleton
What are the 3 types of vascular C.T. (Blood)
plasma
cells
fibers (fibrinogen-fibrin)
What are 3 of blood cells
RBS (erythrocytes)
WBC (leukocytes)
-neutrophil, eosinophil, basophil, monocyte, lymphocyte
Platelets(fragments)
Characteristics of blood C.T.
Fibers: fibrin (during coagulation) cell: hemacytoblast Matrix: plasma -transport of nutrients, waste, gases & others, coagulation process, maintain temp, PH; prevent infection -cardiovascular sys
What are the 3 types of muscle tissue
smooth -> non striated & involuntary
Skeletal ->striated & voluntary
Cardiac ->striated & involuntary
What is smooth muscle
- actin/myosin
- contraction slow & lengthy
- cell is fusiform, short, can divide & repair itself
- matrix is plasma
- generally innervated in grps (motor units) joined via gap junctions, others innervated separately (ex. arrector pili & muscles of iris)
- muscularis of organs
What is skeletal muscles
fibers: lots of collagen and elastin
- cells: very long, cannot divide they die become replaced by C.T.
- ambulation, voluntary movement
- muscles attached to bones, to skin or to the C.T. covering other muscles
What is the cardiac muscle
- has cardiac stimulator so no innervation to contract
- joined by intercalary disks/ desmosomes/ gap junctions, can’t divide or regenerate
- linked to 2 motor units atria or ventricles
- pump blood
What are two types of nervous tissue
- brain & spinal cord
- nerves/accessories
what are 2 types of nerve cells
neuron: excitable
Glial cells: not excitable; nourish, support & assist neurons
What does nervous tissue/system do
give instruction, basis of homeostasis
What are 4 types of membranes
- cutaneous (covers body surface / skin)
- mucous (lines body surfaces opening to exterior)
- serous (lines cavities)
- synovial (lines joint cavities)
What is cutaneous membrane
- epidermis (keratinized stratified squamous epithelium)
- dermis (C.T.)
What is mucous membrane
- secretes mucus via goblet cells (except urinary) that lubricates, thus preventing drying
- secretes digestive enzymes
- protects from pathogens
- collects particles (respiratory)
- lines cavities that are open to the exterior
What is serous membrane
- pleura (thoracic cavity/ lungs)
- peritoneum (abdominopelvic / organs)
- pericardium (cardiac cavity/ heart)
What is synovial membrane
- areolar C.T.rich in elastic fibers & adipocytes; no epithelial tissue
- synovial liquid: viscous (hyaluronic acid) lubricates & nourishes cartilage, decrease friction,fills articular cavities
- lines articulations & tendon sheaths of hands & feet
Tissues have ______ capacity to regenerate and repair itself
variable
What is striated muscle & neurons capacity to repair
Lose its capacity to divide in the adult
What is epithelium and C.T. capacity to repair itself
regenrates from non differentiated stem cells
what is liver cells (from glandular epithelium from endoderm) capacity to repair itself
can divide via mitosis
What is endothelial cells of blood vessels capacity to repair itself
can divide via mitosis
What are 6 factors that affect tissue repair
- age
- ample irrigation
- state of health
- type of lesion
- type of tissue reached
- nutritive substances (proteins & vitamins)
What helps promote tissue repair
- vitamin A,C,E (antioxidants, protect cell membrane by neutralizing free radicals that are toxic)
- Vitaimin C (citric acid: lack weakens blood vessels & healing doesnt occur)
- vitamin K (aid w/ coagulation)
3 stages of tissue repair
- inflammation sets the stage
- organization restores the blood supply
- regeneration and fibrosis effect permanent repair
What happens in stage 1 tissue repair
inflammation
- severed blood vessels bleed
- inflammatory chems released
- local blood vessels become more permeable, allowing WBC, fluid, clotting proteinsand other plasma proteins to seep into the injured area
- clotting occurs, surface dries and forms a scab
What happens in stage 2 of tissue repair
Organization
- clot is replaced by granulation tissue, which restores vascular supply
- fibroblasts produce collagen fibers that bridge the gap
- macrophages phagocytize dead and dying cells and other debris
- surface epithelial cells multiply and migrate over the granulation tissue
What is stage 3 of tissue repair
regeneration and fibrosis
- the fibrosed area matures & contracts; the epithelium thickens
- a fully regenerated epithelium w/ an underlying area of scar tissue results
