Tissues Flashcards Preview

BMS101 > Tissues > Flashcards

Flashcards in Tissues Deck (44):

Define Tissue

Tissue: A group of cells performing similar functions

-vary in structure, function & content of their extracellular matrix (can contain protein fibres, salts, H20 & dissolved macromolcules)


4 Types of Tissues

1. Epithelial Tissue
2. Connective Tissue
3. Muscle Tissue
4. Nervous Tissue


Epithelial Tissue - 6 General characteristics

*Lines every body surface and all body cavities (organs lined on the outside and inside & majority of glands are derived from epithelial tissue)
1. Cellularity: composed almost entirely of cells - little extracellular matrix w/ cells bound together w/ intercellular junctions
2. Polarity - have apical suface & basal surface (i.e. lots of channels - one side of cell exposed, other not)
3. Attachment - Basal surface attached to thin basement membrane
4. Avascularity - lack blood vessels (nutrients via diffusion from underlying tissue)
5. Innervation - Richly innverated to detect changes in enviro
6. Regeneration - apical surface in constant contact w/ enviro (freq. damaged/die)
-replaced quickly


4 Functions of Epithelial Tissue

1. Physical Protection: From dehydration & abrasion (phys. chem. bio.)
2. Selective Permeability: needs to absorb certain things from enviro.
3. Secretions: exocrine cells produce secretions such as sweat & oil (may be scattered amount other cell types in epithelium or may form a gland)
4. Sensations: possess nerve endings that can detect light, taste, sound, smell & hearing


Basement Membrane

-is a specialised structure of epithelium
-found between epithelium & underlying connective tissue
-provides physical support and anchoring of epithelial tissue
-acts as barrier to regulate passage of large molecules between epithelium & underlying connective tissue

*is actually composed of 3 layers that all strengthen attachment & form a selective barrier


Intercellular Junctions - 4 types

*Epithelial cells strongly bound to each other by sharing membrane specialisations
4 types;
1. Tight junctions
2. Adhering Junctions
3. Desmosomes (or hemidesmosomes)
4. Gap junctions


Tight Junctions

-Encircle cells near apical surface
-Prevents molecules from travelling between - must go through epithelial cells to reach basal membrane (are therefore gatekeepers)
-provides structure & support at apical surface.

-in small intestine, prevent digestive enzymes that degrade molecules from moving between epithelial & connective tissue


Adhering Junctions

-Formed completely around the cell deep to tight junctions
-microfilaments act like a purse string to stabilise the apical surface (is a strengthening belt of the cell)
-provide a small space between neighbouring cells in direction of basal surface = passage between cells for materials that have already passed through epithelial cell



-Doesn't totally encircle cell
-Like a button or snap between adjacent cells - joins cells together
-At places of mechanical stress between cells
-Have thickened protein plaque on each of apposed cell membranes w/ fine network of proteins spanning intercellular space
-On cytoplasmic side, intermediate filaments attach to plaques & provide suppot and stability


Gap Junctions

-Fluid filled channels that directly connect the cytoplasms of apposed cells sharing these structures
-allow adjacent cells to communicate w/ each other by flow of ions & other small molecular messengers (i.e. glucose, a.a.)

i.e. muscle cells for contraction along muscle - might need communication along.


Epithelia Classification

*classified based on shape of cells (at most superficial surface) & no. of cell layers


Epithelial Cell Shapes (3)

1. Squamous: flattened, wide, irregular w/ large nucleus (like a fried egg)
2. Cuboidal: about same size on all sides - nucleus centrally located (but do NOT have edges)
3. Columnar - taller than they are wide (nucleus is oval & located in basal region)


Epithelium Cell Layers (3)

1. Simple Epithelium: single layer of cells w/ all cells having apical surface & attached to basement membrane (apical often covered by thin layer of fluid or mucus for protection)
-found where stress minimal & absorption, filtration or secretion is primary function
2. Stratified epithelium - 2+ layers (not all have apical surface or attach to basal membrane)
-areas subject to abrasive or mechanical stresses
3. Pseudostratified epithelium - single layer - not all cells reach apical surface
-Nuclei give appearance of multilayered, stratified epithelium (those that do reach often have cilia to help move fluid along)


Types of Epithelium & Location (Simple)

-Simple Squamous Epithelium: single layer of flat cells (allows rapid diffusion: lungs, blood vessels & membranes that cover body cavities)
-Endothelium (lines lumen of blood & lymphatic vessels & heart & its chambers
-Mesothelium (serous membrane that lines internal walls of pericardial, pleural & peritoneal cavities)
-Simple Cuboidal: forms ducts of exocrine glands (gen. involved in absorption & secretion)
-Simple columnar: I.e. small intestine (involved in absorption & secretion
-Simple Columnar Ciliated - Possess cilia on apical surface such as in respiratory and reproductive systems


Types of Epithelium & Location/function (Stratified)

-Stratified Squamous Cells - in areas w/ lots of stress as provide protection for underlying tissue
-either exists as nonkeratinized (remains alive w/ mucous or saliva) or keratin (apical = cells that are deal & lack a nucleus - such as outer layer of skin)
-Stratified Cuboidal Epithelium: Generally found in glandular tissue (i.e. sweat or semen), although function is mainly protective (serves to strengthen wall of gland ducts)
-Stratified Columnar - quite rare to fine (e.g. male urethra)
-Psuedostratified Columnar - not really stratified as all cells in contact w/ basement membrane - looks stratified as not all cells reach apical surface.
-often covered w/ cilia, generally involved in protection
-found in respiratory tract, naval cavity


Transitional Epithelium - what it is, where found & distinct Feature

-Found in the lining of the urinary bladder
-Changes shape between squamous and cuboidal depending on whether bladder if full or empty (walls stretched or contracted)
-when stretched: resemble squamous cells
-When relaxed: polyhedral (many sided)
-Distinct feature: presence of few binucleated cells
-Cells aren't uniform - are bunched up


Glands - Function

-2 Categories

Definition of Duct

-Perform secretory function
-produce mucin, hormones, enzymes & waste products

2 categories;
1. Exocrine glands: possess ducts that cells secrete products into - almost all derived from epithelial tissue
-i.e. milk, sweat, mucous, saliva glands
2. Endocrine Glands: do not possess ducts - cells secrete products into interstitial fluid or bloodstream - derived from multiple tissue
-i.e. hormones

Duct: epithelium lined tube through which secretions of glands are discharged to epithelial surface


Connective Tissue - Overview

-Is most diverse, abundant, widely distributed and structurally varied of all tissue types
-serves to connect structures together
-Is the glue AND filler of the body
-designed to support, protect & bind organs`

e.g. tendons, ligaments, body fat, bones & cartilage


3 structural components of Connective Tissue

1. Cells: differ between types of connective tissue (CT)
-i.e. fibroblasts produce fibres, adipocytes = fat, chondrocytes = cartilage
2. Protein Fibres: elastic fibres (flexibility), collagen (strength), reticular fibres (interwoven framework)
3. Ground Substance: mix of proteins & carbs w/ variable amounts of salts and H2O

-Protein fibers and ground substance comprise extracellular matrix - produced by CT cells
-Most CT = mainly extracellular matrix w/ small portion of cells (relative to epithelial)).

*Different connective tissues vary in these components


Protein fibres in CT (3)

-Elastic fibres
-collagen fibres
-Reticular fibres


6 Functions of connective tissues

1.Physical protection - fat can protect kidneys, axial cavity can protect brain, heart, lungs
2. Binding of structures - e.g. ligaments, tendons
3. Support and structural frameworks - bones allow soft tissue to connect
4. Storage - fat for energy, Bone for Ca & P
5.Transport - blood transports nutrients
6. Immune Protection - WBC can ward off infection/disease
-extracellular matrix is viscous material that interferes w/ movement and spread of disease-causing organisms


3 Broad classifications of Connective Tissues

1. CT Proper
2. Supporting CT
3. Fluid CT


Connective Tissue Proper - 2 Categories (3 types within each category)

1. Loose CT: fewer protein fibres & more ground subs.
- serves as body's packing material - found in spaces around organs
*3 types: areolar, adipose, reticular
2. Dense CT: More proteins & less ground subs.
*3 types: dense regular, dense irregular, elastic


Loose CT; Areolar

-contains fibroblasts, collagen & elastic fibres
-Can be distorted w/out damage
-provides shock absorption
-found subcutaneous to skin
-found nearly everywhere: surrounds nerves, blood vessels & individual muscle cells


Loose CT; Adipose

-known as "fat"
-comprised mainly of adipocytes (fat cells) and little else (nuclei pushed to peripheral of cells
-serves to pack around structures & provide padding, cushion shocks & acts as an insulator

-if adipose cells increase fat stores = lipogenesis
-if decrease fat stores = lipolysis

*Fat cells can NOT divide - mesenchymal cells provide extra fat cells if body has excess nutrients


Loose CT; Reticular

-contains reticular fibres, fibroblasts & leukocytes
-found in spleen, lymph node & bone marrow
-Provides structural support


Dense Connective Tissue - characteristics

-Is strong, has fibres (mostly collagen) packed tightly together
-less ground substance than loose connective tissue


3 types of dense connective tissue

1. Dense regular CT
2. Dense irregular CT
3. Elastic CT


Dense CT; Dense Regular

-collagen fibres aligned parallel to applied force
-found in tendons (muscle to bone) and ligaments (bone to bone)
-few blood vessels - takes long time to heal following injury (rich blood supply necessary for good healing)


Dense CT; Dense Irregular

-bundles of collagen fibres extending in different directions
-found in deep portions of skin (dermis) & capsules around organs such as liver, kidney & spleen
-forms supporting layer around cartilage & bone (except in joints)
-In places where you'd need to deal with forces from different directions.


Dense CT; Elastic CT

-predominantly elastic fibres that provide ability to stretch and recoil
-found in voal cords & large/medium arteries & suspensory ligament of penis


Two cell groups in CT proper
-examples (4 in each)

1. Resident cells (permanently in CT)
-Fibroblasts: most abundant in CT proper; produces fibres & ground sub. components of ECM
-Adipocytes - small clusters or as adipose tissue (if large cluster)
-Fixed macrophages - large irregular cells which phagocytose dead cells or pathogens - release chem. which stimulate immune response
-Mesenchymal cells - embryonic stem cell - differentiates into required CT cell
2. Wandering Cells - primarily Leukocyte type (WBC) [no. at particular moment depends on local conditions]
-mast cells: usu found close to blood vessels - involved in clotting and dilation of vessels
-plasma cells: synthesises disease fighting proteins called antibodies - usu found in intestinal walls, spleen & lymph node
-free macrophages: mobile phagocytic cells that are formed from monocytes; engulf and destroy and bacteria, foreign particles or damaged cell/debris
-Other leukocytes migrate through blood vessel - majority = neutrophils (seeks out bacteria)


Fibres of Connective Tissue Proper (3)

*produced by CT cells and secreted in ECM
1. Collagen Fibres: long, unbranching, strong, flexible and resistant to stretching; make up 25% of all protein; found in ligaments & tendons - parallel struct. allows them to withstand enormous force in that direction
2. Elastic Fibres: thinner than collagen, stretch easily (due to coiled struct.), branch & then rejoin; allow structures (blood vessels, skin, lungs, arteries) to stretch & relax
3. Reticular Fibres: thinner than collagen, form a meshwork-like configuration; act as packing material & provide structural support for certain organs. Found in organs w/ abundant spaces: liver, lymph nodes & spleen


Ground substance of Connective Tissue Proper

-Is a colourless, featureless, viscous solution that has a gelatinous, rubbery consistency
-Is a combo of proteins and carbs
-additional content such as H2O & salts can result in texture that is semi-fluid to hard


Two Types of supporting Connective Tissue (identify only)

1. Cartliage
2. Bone


4 Components of Fluid Connective Tissue

1. Plasma: watery ground subs. containing protein fibres
2.Erythrocytes: red blood cells
3. Leukocytes: White blood cells
4. Platelets: Fragments of blood cells involved in blood clotting


Muscle tissue - composition & basic outline as to function

-Comprised of cells called fibres
-When stimulated by nervous system, fibres shorten or contract - resulting in movement


3 Types of Muscle

1. Skeletal: multinucelated, long cylindrical, striated fibres
-moves skeleton
-Responsible for voluntary body movement
-attaches to bone or skin - found in voluntary sphincters
2. Cardiac: one/two nuclei, short bifurcated and striated fibres w/ intercalated discs
-involuntary contractions & relation pump blood in heart (heart wall - myocardium
3. Smooth: non sriated, spindle shaped (fusiform) w/ central nucleus
-involuntary movements and motion
-found in walls of internal organs - vessels, airways, bladder, stomach, uterus
-helps propel & control movement of material through these organs


2 types of Cell in Nervous Tissue

-function of nervous tissue

1. Neurons: nerve cells that are capable of initiating and conducting electrical activity throughout body
-are the longest cell in the body
2. Neuroglia: cells that support the neurons (are a supportive network)

*Function: communication and control of body function


Body Membranes - where they are

-4 Types

-Found in major body cavities that line the internal and external cavity surfaces.

1. Mucous
2. Serous
3. Cutaneous
4. Synovial


Mucous Membranes (Mucosa)


-Lines body passageways
-connective tissue - lamina propria
-Has absorptive, secretory and protective roles
-mucous cells prevent drying out - lubricate and trap foreign substances
-Found: digestive, respiratory, reproductive and urinary tracts


Serous Membranes (Serosa)

-composed of
-where found

-simple squamous epithelium - mesothelium
-Parietal and visceral serous layers
-Found; pleura (around lungs), pericardium (around heart) & peritoneium (around abdomin)


Cutaneous membranes (skin)

-largest membrane in body
-keratinised stratified squamous epithelium
-connective tissue - dermis (also w/ epidermis)
-protects body from external enviro & prevents water loss


Synovial membranes - joint lining

-composed of well-vascularised areolar, fibrous or adipose connective tissue
-secretes synovial fluid that reduces joint friction and provides nutrients to the joint surfaces