Histology Flashcards
4 basic tissue types
epithelial tissue (epithelium
connective tissue
muscle tissue
nervous tissue
epithelial tissue characteristics
large sheets of cells covering all surfaces of body (exposed to outside) lining organs, internal cavities and passageways
highly cellular
cell junctions: adjoining cells form specialized intercellular connection between their cell membrane
avascular
capable of rapidly replacing damaged and dead cells,
function of epithelial tissue
provides protection from physical chemical and biological wear and tare, many have barriers with selective transportation of molecules, capable of secretion and release mucous
in small intestine, repiratory tract, etc.
tight junction
in epithelial tissue, separates the cells into apical and basal compartments, tight junctions seal cells together (material can’t get through)
anchoring junction
stabilize epithelial tissues, in lateral and basal surfaces of cells provide strong / flexible connections
desmosomes
patches on membrane of cells made of structural proteins on the inner surface of the cell’s membrane, hold cells together
hemidesmosomes
link cells to the extracellular matrix ex: basal lamina
adheren junctions
connect isolated patches or form belt like structure inside cell, influence shape and folding of epithelial tissue, characterized by presence of contractile protein actin on cytoplasm
gap junction
forms an intercellular passageway between membranes of adjacent cells, facilitates movement of small molecules and ions between cytoplasm and cells, allow electrical and metabolic coupling of adjacent cells which coordinates function in large groups of cells
shapes of epithelial tissue
squamous, cuboidal, columnar
simple epithelium
one cell layer, every cell rests on basement membrane
stratified epithelium
more than one layer, only basal layer of cells rests on basement membrane
pseudo-stratified
describes tissue with a single layer of irregularly shaped cells that give the appearance of more than one layer
transitional
describes a form of specialized stratified epithelium in which shape of the cells can vary
Simple squamous
Structure: appearance of thin scales. Squamous cell nuclei tend to be flat, horizontal, and elliptical, mirroring the form of the cell
Function: diffusion, filtration, provide a smooth and protective surface. secrete a fluid that lubricates the mesothelium,
Location: air sacs and alveoli, lining of blood vessels, serous membranes lines vessels of the lymphatic and cardiovascular system, is present where rapid passage of chemical compounds is observed, alveoli of lungs where gases diffuse and the lining of capillaries, mesothelium is a simple squamous epithelium that forms the surface layer of the serous membrane that lines body cavities and internal organs
simple cuboidal
Structure: the nucleus of the box-like cells appears round
Function: absorption and secretion active in the secretion and absorption of molecules
Location: kidney tubules, glands near the center of the cell, lining of the kidney tubules and in the ducts of glands
Simple columnar
Structure: the nucleus of the tall column-like cells tends to be elongated and located in the basal end of the cells, composed of simple columnar epithelial cells with cilia on their apical surfaces
Function: absorption, secretion, movement (if ciliated)
Location: forms the lining of some sections of the digestive system, namely the stomach, small intestine, and large intestine, lining of the uterine tubes, where the beating of the cilia helps remove particulate matter
pseudo-stratified columnar
Structure: appears to be stratified but instead consists of a single layer of irregularly shaped and differently sized columnar cells, nuclei of neighboring cells appear at different levels rather than clustered in the basal end, all the cells are in contact with the basement membrane, although some do not reach the apical surface
Function: protection, movement
Location: lines respiratory tract
stratified squamous
Structure: several stacked layers of cells
Function: protection
Location: epidermis of skin, lining of the oral cavity, pharynx, esophagus, anus, and vagina
transitional
Structure: appears thicker and more multi-layered when the bladder is empty, and more stretched out and less stratified when the bladder is full and distended
Function: distention and relaxation of urinary structures
Location: lining of uterus, bladder, and urethra
Endocrine gland
hormones, released into interstitial fluid, to blood stream to cell receptors, regulatory system coordinates the regulation and integration of body responses
ex: anterior pituitary, thymus, adrenal cortex, gonads
Exocrine glands
release contents through a duct that goes to epithelial surface
ex: mucous sweat saliva, breast milk, secretion of gastrointestinal tract
merocrine secretion
most common of exocrine, secretions enclosed in a vesicle that move to apical surface of cell and released by exocytosis
ex: eccrine gland that produces sweat,
apocrine secretion
accumulates near apical surface of cell and is pinched off from cell and released
ex: mammary glands
holocrine secretion
rupture and destruction of entire gland cell, accumulate secretory products and releases them when they burst
ex: sebaceous glands, (oils on skin and hair)
Connective Tissue
structure: sparse cells in extracellular matrix (protein fibers and ground substance
function: physical protection, support structural framework, binding of structures, storage, transport, immune protection
Types of connective tissue
all derive from mesodermal layer of embryo
connective tissue proper, (loose and dense), supportive connective tissue (bone and cartilage)
fluid connective tissue (lymph and blood)
extracellular matrix
polysaccharides and proteins secreted by fibroblasts combine with extra-cellular fluids to produce a viscous ground substance with embedded fibrous proteins
ground substance
secreted by fibroblasts, made of polysaccharides, hyaluronic acid, and proteins,
then combine to form a proteoglycan with a protein core and polysaccharide branches
proteoglycan attracts and traps moisture forming the clear viscous colorless matrix of ground substance
Collagen fiber
made of fibrous proteins linked together to form protein subunits linked together to form long straight fiber, flexible, have strength, resist stretching, give ligaments and tendons characteristics of resilience and strength, hold connective tissues together
elastic fiber
contains protein elastin and other proteins, after being stressed and compressed returns to original shape, in tissues found in skin and elastic ligaments of the vertebral column
Reticular fiber
from fibrous protein subunits, but are narrow and in a branched network, all throughout the body but most abundant in reticular tissue of soft organs such as liver and spleen, anchor and provide structural support of the functional cells, blood vessels, and nerves of the organ
3 types of fiber in connective tissue proper
collagen fiber, elastic fiber, reticular fiber
Cells present in connective tissue proper
fibroblast, adipocytes, mesenchymal cells, macrophage
fibroblast
most abundant cell in connective tissue proper
secretes polysaccharides and proteins
Adipocytes
cells that store lipid as droplets that fill most of the cytoplasm
mesenchymal cells
adult stem cell that can differentiate into any type of connective tissue, cells needed for repair and healing of damaged tissue
macrophage
large cell derived from a monocyte (type of blood cell), part of immune system to defend against pathogens and degrade host cells, release cytokines (small protein that act as chemical messenger, recruit other cells to infected sites and stimulate their activities, move with amoeboid movement engulf infectious agents and cellular debris, fix macrophage don’t move
Areolar Tissue
Structure: shows little specialization. It contains all the cell types and fibers previously described and is distributed in a random, web-like fashion
Functions: fills the spaces between muscle fibers, surrounds blood and lymph vessels, and supports organs in the abdominal cavity
Location: underlies most epithelia and represents the connective tissue component of epithelial membranes
Adipose tissue
Structure: consists mostly of fat storage cells, with little extracellular matrix
Functions:rapid storage and mobilization of lipid molecules serve as insulation from cold temperatures and mechanical injuries
Location:
Reticular tissue
Structure: mesh-like, supportive framework for soft organs such as lymphatic tissue, the spleen, and the liver
Functions: produce the reticular fibers that form the network onto which other cells attach
Location: lymphatic tissue, spleen liver
Dense Regular connective tissue
Structure: fibers are parallel to each other
Functions: enhancing tensile strength and resistance to stretching in the direction of the fiber orientations
Location: Ligaments and tendons
Dense irregular connective tissue
Structure: contains fibers reaching in all directions
Functions: gives the tissue greater strength in all directions and less strength in one particular direction
Location: dermis of the skin
Dense Elastic tissue
Structure: contains elastic fibers in addition to collagen fibers
Functions: allows the tissue to return to its original length after stretching
Location: ligaments in the vocal folds and between the vertebrae in the vertebral column, arterial walls and bronchial walls (airways
Connective tissue types (cartilage and bone)
Cartilage consists of chondrocytes found in a semisolid matrix. Bone consists of osteocytes found in a calcified, solid matrix.
Fluid Connective tissue (blood and lymph)
Blood consists of several cells types that circulate in a liquid extracellular matrix called plasma. Erythrocytes, red blood cells, transport oxygen and some carbon dioxide. Leukocytes, white blood cells, are responsible for defending against potentially harmful microorganisms or molecules. Platelets are cell fragments involved in blood clotting. Nutrients, salts, and wastes are dissolved in the liquid matrix and transported through the body.
Lymph has liquid matrix and white blood cells.Lymph drains into blood vessels, delivering molecules to the blood that could not otherwise directly enter the bloodstream. In this way, specialized lymphatic capillaries transport absorbed fats away from the intestine and deliver these molecules to the blood.
Scurvy
- Caused by Vitamin C deficiency
- Normal collagen fibers cannot form
- Weakening of gums, teeth, bones and internal mucosa
- Wounds and fractures don’t heal well
- Prevalent among sailors
Marfan Syndrome
- gene on chromosome 15
- Abnormalities in fibrillin, the anchor and coat for elastin
- Causes skeletal, cardio, vision, and connective tissue abnormalities
- Tall and thin with long legs, arms, fingers, and toes
- Typically die by age 50 because of heart weakness
Gangrene
- Most commonly affects limbs, fingers and toes
- May b caused by lack of blood flow, mechanical injury, bacterial infection or diabetes
•Dry gangrene, wet gangrene, gas gangrene
Collagen Fiber
made from fibrous protein subunits linked together to form long straight fiber, flexible but strong, resist stretching, give ligaments and tendons resilience and strength, hold connective tissues together
Elastic fiber
contain protein elastin and other proteins / glycoproteins, after stretched and compressed it will return to original form, in elastic tissues, skin, elastic ligaments of vertebral column
Reticular fiber
formed from same protein subunits as collagen fibers, narrow, in branching network, all through body but most abundant in reticular tissue of soft organs (liver and spleen) anchor and provide structural support to the functional cells, blood vessels, and nerves of the organ
fibroblast
most abundant cell in connective tissue proper, secretes polysaccharides and proteins
adipocytes
cells that store lipids as droplets that fill most of the cytoplasm
mesenchymal cell
multipotent adult stem cell, can differentiate into any type of connective tissue cells needed for repair and healing damaged tissue
machrophage
large cell derived from monocyte, type of blood cell, enters into connective tissue matrix from blood vessels, help with immune system, move rapidly by amoeboid movement and engulf infectious agents and cellular debris, others remain permanent in tissues
