Ch5 Histology Flashcards
What is histology?
Study of tissues and their arrangement into organs
What are tissues?
A group of similar cells working together to perform specific role within organ
What are the 4 primary tissues?
- Muscular
- Epithelial
- Nervous
- Connective
Describe epithelial tissue
- sheet of closely adhering cells
- apical (upper) surface exposed to environment or an internal space, so it covers surfaces & lines cavities
- avascular
- basal (lower) surface sits on basement membrane -collagen & laminin & fibronectin adhesive glycoproteins
What’s the difference between simple epithelium and stratified epithelium?
- Simple epithelium vs. Stratified epithelium
- -1 cell layer - multilayered
- -named for shape - named for shape of apical cells
- -all cells touch basement membrane - “upper” cells do not touch basement membrane
Describe simple squamous epithelium
- single layer, thin cells
- permits rapid diffusion / transport
- alveoli, glomeruli, endothelium, and serosa
Describe simple cuboidal epithelium
- single layer, square / round cells
- absorption & secretion
- Liver, thyroid, mammary & salivary glands, kidney tubules
Describe simple columnar epithelium
- single layer, tall narrow cells
- goblet cells
- absorption; secretion of mucus
- lining of GI tract, uterus, uterine tubes
Describe pseudostratified epithelium
- looks multilayered; some not reaching free surface; all touch basement membrane
- cilia & goblet cells
- trachea, portions of male urethra
Describe keratinized stratified squamous
- layer of dead scaly cells at surface
- resists abrasion; retards water loss; resists bacterial invasion
- skin epidermis; palms & soles of feet heavily keratinized
Describe nonkeratinized stratified squamous
- no keratinized layer
- resists abrasion & pathogen invasion
- tongue, oral mucosa, esophagus, vagina
Describe stratified cuboidal epithelium
- two or more cell layers; surface cells square / round
- sweat gland ducts, ovarian follicles, seminiferous tubules
Describe transitional epithelium
- multilayered epithelium surface cells; change from round to flat when stretched
- renal pelvis, ureter, bladder
Describe connective tissues
- cells & fibers in extracellular material (matrix)
- matrix = fibrous proteins + ground substance
- binds organs to each other, supports & protects organs
- highly vascular
What are the 3 fibrous proteins in connective tissues?
- Collagen fibers
- Reticular fibers
- Elastic fibers
Describe collagen fibers
- most abundant of body’s proteins—25%
- tough, flexible, resists stretching
- tendons, ligaments, & deep layer of skin: mostly collagen
Describe reticular fibers
- thin collagen fibers coated w/ glycoprotein
- form framework of such organs as spleen & lymph nodes
Describe elastic fibers
- made of elastin protein
- allows stretch & recoil
Describe the ground substance part
- Usually gelatinous / rubbery consistency due to 3 classes of large molecules:
- glycosaminoglycans (GAG)
- proteoglycans
- adhesive glycoproteins—bind components of tissues together
What are the types of fibrous connective tissue?
- Areolar
- Reticular
- Dense regular
- Dense irregular
Describe areolar tissue (loose fibrous)
- loosely organized fibers
- underlies all epithelia, mesenteries, between muscles
Describe reticular tissue (loose fibrous)
- mesh of reticular fibers & fibroblasts
- forms supportive stroma (framework) for lymphatic organs
- lymph nodes, spleen, thymus, bone marrow
Describe regular connective tissue
- densely packed, parallel collagen fibers
- compressed fibroblast nuclei
- elastic tissue/fibers, wavy sheets
- tendons & ligaments
Describe dense irregular connective tissue
- densely packed, randomly arranged, collagen fibers, few cells
- withstands unpredictable stresses
- dermis of skin; capsules around organs
Describe adipose tissue
- adipocytes = dominant cell type
- energy reservoir
- quantity of stored triglyceride, # of adipocytes quite stable
- fat recycled continuously to prevent stagnation
- thermal insulation
- most adult fat called white fat
- brown fat in fetuses, infants = heat-generating tissue
- anchors and cushions organs such as eyeballs and kidneys
Describe cartilage
- supportive connective tissue w/ flexible, rubbery matrix
- chondroblasts produce matrix
- chondrocytes = cartilage cells in lacunae
- perichondrium = sheath of dense irregular tissue
- gives shape to ear, tip of nose, larynx
- avascular - relies on diffusion; heals slowly
What are the 3 types of cartilage?
- Hyaline
- Elastic
- Fibrocartilage
Describe hyaline cartilage
- clear, glassy appearance due to fineness of collagen fibers
- articular cartilage, costal cartilage, trachea, bronchi, larynx
Describe elastic cartilage
- cartilage w/ elastic fibers
- external ear, epiglottis
Describe fibrocartilage
- cartilage containing large, coarse bundles of collagen fibers
- pubic symphysis, menisci, intervertebral discs
Describe bone and the parts of it
tissue w/ solid matrix; calcified
- osteocytes = mature bone cells in lacunae
- canaliculi—delicate canals that radiate from each lacuna; allow osteocytes to contact each other
- osteon—central canal + surrounding lamellae
- periosteum - tough fibrous connective tissue covering of bone
Describe compact bone
compact bone – cylinders that run longitudinally through shafts of long bones; Haversian canal in center
Where is bone matrix deposited in?
Concentric lamella
Describe blood
fluid connective tissue
What is plasma?
Blood’s liquid ground substance
What are the formed elements of blood?
- Erythrocytes—red blood cells
- Leukocytes—white blood cells
- Platelets—cell fragments involved in clotting
Describe nervous tissue
specialized for communication by electrical & chemical signals
- consists of neurons
- detect stimuli, respond quickly
- neuroglia (glial)
- protect & assist neurons; “housekeepers” of nervous system
- neurosoma, dendrites, axons
Describe muscular tissue
elongated cells specialized to contract in response to stimulation
- exert physical force on other tissues
- creates movements - limb movement, digestion, waste elimination, breathing, blood circulation
- important source of body heat
What are the 3 types of muscle?
- Skeletal
- Cardiac
- Smooth
Describe skeletal muscle
long cells, called muscle fibers
- most attach to bone
- multinucleate - adjacent to plasma membrane
- striations - alternating dark & light bands
- voluntary - conscious control
Describe cardiac muscle
- only in heart!!
- cardiocytes - short & branched
- intercalated discs join cardiocytes end to end (provide electrical & mechanical connectivity)
- striated and involuntary
Describe smooth muscle
- relatively short, fusiform cells
- 1 central nucleus
- visceral muscle—forms layers of digestive, respiratory, & urinary tracts, blood vessels
What do cell junctions do?
Keep cells together so they don’t fall apart
What are the types of cell junctions?
- tight junctions
- desmosomes
- gap junctions - connexons
What are the types of glands?
Endocrine and exocrine
Describe endocrine glands
- secretions go directly into blood
- secretions = hormones
- thyroid, adrenal, & pituitary glands
Describe exocrine glands
- Release material by way of duct
- sweat, mammary, & tear glands
What are the structures of exocrine glands?
- capsule
- stroma - framework
- parenchyma – secreting cells
What are the types of exocrine glands?
- Simple v. Compound
- Shape: Acinar v. Tubuloacinar
What are the types of secretions?
- Serous glandsthin, watery secretions (sweat, milk, tears, digestive juices)
- Mucous glands (produce mucin that absorbs water to form sticky secretion called mucus)
- Mixed glands
- Cytogenic glands release whole cells (testes & ovaries)
Describe the mode of secretion for eccrine (merocrine) glands
secrete by exocytosis
-tear glands, pancreas, gastric glands, mammary glands
What is the mode of secretion for aprocrine glands?
blebs w/ material come off cells
-axillary sweat glands, mammary glands
What is the mode of secretion for holocrine glands?
cells accumulate product, then entire cell disintegrates
secretion = mixture of cell fragments & synthesized substance
oil glands of scalp
What are the membrane types?
- Cutaneous membrane = skin (relatively dry layer; protection)
- Synovial membrane lines joint cavities (connective tissue layer only, secretes synovial fluid)
- Serous membrane (serosa) – internal membrane (covers organs & lines walls of body cavities; produces serous fluid)
- Mucous membrane (mucosa) – internal membrane (lines passages that open to exterior environment)
What are the types of tissue growth?
- Hyperplasia—tissue growth through cell multiplication
- Hypertrophy—enlargement of preexisting cells
- Neoplasia—development of a tumor (neoplasm)
What are the changes in tissue?
- Differentiation= unspecialized embryonic tissues –> specialized mature types
Ex. - mesenchyme –> muscle
- Metaplasia=changing from one type of mature tissue to another
Ex. - simple cuboidal tissue –> stratified squamous after puberty
What are the types of tissue repair?
- Regeneration - replacement of damaged cells w/ original cells (skin & liver)
- Fibrosis - replacement of damaged cells with scar tissue; function not restored (muscle, lung tissue (TB), severe cuts/burns of skin)
- Keloid is healing w/ excessive fibrosis (raised shiny scars)
What are the different types of stem cells?
- totipotent=cells become anything
- pluripotent= can become a lot but not everything
- multipotent= more specialized, can become one thing but not the other
What are the types of tissue degeneration and death?
- Atrophy—shrinkage of tissue through loss in cell size or number
- Apoptosis—programmed cell death
Define necrosis
- premature, pathological death of tissue due to trauma, toxins, or infections
- infarction – sudden cell death
Define gangrene
- tissue necrosis from infection or lack of blood supply
- Dry v. Wet
Describe tissue repair
Healing of a cut in the skin
Blood plasma seeps into wounds carrying…
- antibodies
- clotting proteins
- blood cells
What do scabs do?
Temporarily seals wounds and blocks infections
