TISSUES

HONORS ANATOMY & PHYSIOLOGY

• 4 basic types of tissues in human body contribute to homeostasis by providing diverse functions including

• protection• support• communication among cells• resistance to disease • & many more

Tissues & Homeostasis

• a tissue is a group of similar cells that usually have a common embryonic origin & function together to carry out specialized activities

Definition

• their structure & properties are influenced by factors such as: – nature of the extracellular material

surrounding tissue cells– type of connections between cells

Tissues

1. Epithelial – covers body surfaces & lines hollow

organs, cavities, & ducts– forms glands

2. Connective– protects & supports

3. Muscular– movement

4. Nervous – detects changes in/out body & responds by

generating action potentials

Classification of Tissues

1. Epithelial– from all 3 layers

2. Connective– mesoderm

3. Muscular– mesoderm

4. Nervous – ectoderm

Embryology of Tissues

• are contact pts between plasma membranes of adjacent cells

• found between most epithelial cells & some muscle & nerve cells

Cell Junctions

Surfaces of Cells

• thin, extracellular layer• commonly has 2 parts:1. basal lamina2. reticular lamina

Basement Membrane (bm)

• classified according to 2 characteristics:1. # of layers• single layer = simple• multiple layers = stratified• single layer that looks like multiple =

psuedostratified 2. cell shape• squamous• cuboidal• columnar

Covering & Lining Epithelium

• 1 layer of cells, often in sheets• functions:• diffusion/osmosis• filtration• secretion: production & release of

substances (sweat, mucus)• absorption: intake of fluids or other

substances

Simple Epithelium

• appears to have multiple layers because:

1. nuclei @ different layers2. not all cells reach apical surface

Pseudostratified Epithelium

• 2 or more layers of cells– named by shape of top layer

• function: protection where there is considerable wear & tear

Stratified Epithelium

• arranged like floor tiles• very thin: allows for rapid passage of

substance thru cell

Squamous Cells

• shaped like cubes or hexagons• +/- microvilli on apical surface– finger-like cytoplasmic projections– function increase surface area

• function: secretion or absorption

Cuboidal Cell

• taller than they are wide• +/- microvilli or cilia on apical surface– cilia: tiny hair-like projections that beat

in unison: moves substances across surface of cell

• function: • protection • absorption • secretion

Columnar Cells

• single layer flat cells• viewed from– apical surface looks like tiled flooring– cross-section: fried eggs cross section

Simple Squamous Epithelium

• found:• @ sites where filtration (kidneys) or

diffusion (lungs, capillaries) occur• lines blood vessels & chambers in

heart (endothelium), forms lining for serous membranes (mesothelium)

Simple Squamous Epithelium

• nuclei round & centrally located• functions:– secretion– absorption

• found in:– thyroid gland – kidneys

Simple Cuboidal Epithelium

• 2 forms: nonciliated/ciliated• nonciliated simple Columnar

Epithelium– 2 types:1. Columnar epith. w/microvilli on apical

surfaces2. Goblet cells• produce & secrete mucus

Simple Columnar Epithelium

• cilia on apical surface• +/- Goblet cells• functions:–move mucus or any foreign objects

away from lower respiratory tract or ova towards uterus

• found in:– airways of upper respiratory system– fallopian (uterine) tubes

Ciliated Simple Columnar Epithelium

• all cells attached to bm but not all reach apical surface

• Ciliated Pseudostratified Columnar Epith.:

• cells that do reach apical surface either are goblet cells or are ciliated

• Nonciliated Pseudostratified Columnar Epith:

• no cilia or goblet cells

Pseudostratified Columnar Epithelium

• basal layer continually undergoing cell division– as new cells grow, cells near base

pushed upward– as near apical border moving farther

away from their blood supply (in underlying connective tissue) dehydrate, shrink, harden, die cell jcts break down cells sloughed off

Stratifed Squamous Epithelium

Stratified Squamous Epithelium

• Keratinized

• upper layers contain keratin: tough, fibrous protein that protects underlying tissues from heat, microbes, chemicals

• found: skin• Nonkeratinized

• found: lining mouth (buccal mucosa) & esophagus

• protect underlying tissues from wear & tear and from invasion by microbes

• gland: single cell or group of cells that secrete substances into:– ducts – onto a surface – into blood

• classified:1. endocrine– secretions intercellular fluid capillary

2. exocrine– secretions ducts surface of skin or lining of

hollow organ

Glandular Epithelium

Classification of Glands

• most abundant & widely distributed tissue in body

• 2 basic elements:1. extracellular matrix2. cells

Connective Tissue (CT)

• greater % in CT than other tissues• it’s the material located between cells

(secreted by those cells)• determines qualities of the CT• not usually found on surfaces, usually

rich blood supply (x cartilage & tendons)• consists of:– protein fibers– ground substance

Extracellular Matrix

• immature form suffix “blast”– large capacity to divide– secrete matrix

• mature form suffix “cyte”– less likely to divide–maintain matrix

CT Cells

• large flat cells w/ branching processes

• found in most CT• migrate thru CT secreting fibers &

ground substance

Fibroblasts

• develop from monocytes• phagocytes• irregular shape• 2 types:1. wandering– move to sites of infection or inflammation

2. fixed– reside in a particular tissue– ex: alveolar macrophages

Macrophages

• small cells that develop from B lymphocytes

• Important in immune response• most reside in CT– GI & respiratory tracts– lymph nodes, spleen, red bone marrow

Plasma Cells

• found along side blood vessels that supply CT

• produce & secrete histamine: dilates small blood vessels as part of inflammatory response (reaction to injury or infection)

• can also bind, ingest, & kill bacteria

Mast Cells

• aka adipose cells or fat cells• store triglycerides• functions:– store fats for nrg– insulate– cushion organs

Adipocytes

• acellular component of CT that supports cells, binds them together, stores water, provides medium thru which substances are exchanged between blood & cells

• may be:• fluid• semifluid• gelatinous• calcified

Ground Substances

1. Collagen– “colla” = glue a protein (25% of all protein in body!)– very strong fibers that resist pulling

2. Elastic– smaller strong but stretchy fibers– made of protein called elastin– plentiful in skin, blood vessel walls, lung tissue

3. Reticular– made of collagen in fine tubes coated with

glycoproteins forming branching networks & found in BM

– skin, adipose, reticular CT (spleen, lymph nodes)

CT Fibers: 3 Types

1. Areolar CT• 1 of most abundant types• includes all types of CT cells &

fibers• found in: subcutaneous tissue

Mature CT: Loose CT

2. Adipose Tissue• cells: adipocytes• found ass’c with areolar CT• 2 types:1. white– most of the adipose in adults

2. brown– darker due to rich blood supply– widespread in newborns: helps maintain body

temperature

Mature CT: Loose CT

• contains more numerous fibers but fewer cells than in loose CT

• 3 types:1. Dense Regular CT2. Dense Irregular CT3. Elastic CT

Mature CT: Dense CT

• collagen fibers lined up in parallel pattern allowing it to withstand pulling aling axxis of fibers: very strong tissue

• silvery white, tough• ex: tendons & most ligaments

Dense Regular CT

• collagen fibers irregularly arranged• found where pulling forces exerted in

various directions• found: dermis, pericardium,

periosteum

Dense Irregular CT

• predominate fiber: elastic fibers• quite strong & able to return to

original shape after being stretched• found: elastic arteries, lungs

Elastic CT

Membranes

• are flat sheets of pliable tissue that cover or line a part of the body

• 2 types:1. epithelial membrane:– epithelial layer + underlying CT– types: mucous membrane, serous

membrane, cutaneous membrane (skin)

2. synovial membrane:– + CT but - epithelium– line joints

Mucous Membranes (Mucosa)

• line body cavities that open directly to exterior

• line: entire digestive, upper respiratory, & reproductive tracts

• cells connected by tight jcts • Goblet cells secrete

1. mucus slippery so prevents cavities from drying out

2. enzymes from some3. site of nutrient absorption

Serous Membranes (Serosa)• line cavities that do not open directly to

exterior & covers organs w/in those cavities• made of: areolar CT covered by mesothelium

(simple sq. epith.) which secretes serous fluid• 2 layers:1. parietal peritoneum– covers cavity wall

2. visceral peritoneum– covers organs– in pericardial cavity = pericardium– in abd. Cavity = peritoneum

• consists of a dense network of collagen (strength) & elastic (flexibility) fibers, no blood vessels or nerves (x perichondrium) so heals very slowly

• chondrocytes: mature cartilage cells– occur singly or in small groups w/in space

called lacunae

• perichondrium: membrane of dense CT– covers surface of most cartilage

CARTILAGE

• 3 types:1. Hyaline cartilage– most abundant cartilage in body, also the

weakest– provides flexibility & support

2. Fibrocartilage– no perichondrium– provides strength & rigidity (strongest of the 3)

3. Elastic cartilage– + elastic fibers– provides strength & elasticity

Cartilage

• aka osseous tissue• 2 types:1. Compact bone2. Spongy bone

Bone Tissue

• basic unit of compact bone is the osteon (haversian system)

• has 4 parts:1. Lamellae– concentric rings of extracellular material &

collagen– make bone hard & strong

2. Lacunae3. Canaliculi4. Central (haversian) canal)

Compact Bone

• lacks osteons• found only inside compact bone• consists of columns of bone called

trabeculae– spaces between trabeculae filled with

red bone marrow

Spongy Bone

• liquid CT made up of:• Plasma– liquid portion of blood (yellow)– water, dissolved nutrients, wastes, plasma

proteins, hormones, gases, ions

• RBCs: transport O2

• WBCs: phagocytes, immune response, allergic reactions

• Platelets: cell particles involved in blood clotting

Blood

• consists of elongated cells called muscle fibers that can use ATP to generate force movement, maintain posture, generate heat

• 3 types:1. Skeletal2. Smooth3. Cardiac

Muscular Tissue

• most attached to a bone

• muscle fibers up to 12-16 in in longest muscles:–multinucleated (on edges)– striated– voluntary

Skeletal Muscle Tissue

Smooth Muscle Tissue• in walls of hollow internal structures– blood vessels– urinary bladder– intestines

• muscle fibers small, 1 centrally located nuclei, +/- gap jcts– nonstriated– involuntary

• forms wall of heart• muscle fibers are branched with 1

centrally located nuclei– striated– involuntary– *intercalated discs: attach individual

fibers end-to-end (desmosome + gap jct) allows for quicker conduction of action potentials coordinated contractions of heart chambers

Cardiac Muscle Tissue

• 2 cell types:1. neurons– nerve cells that can generate action

potentials which are conducted to other neurons, muscles, or glands

2. neuroglia (glia)– supportive cells to neurons– cannot generate action potentials

Nervous Tissue

Neurons

• electrical excitability: ability to respond to certain stimuli by producing electrical signals (action potentials)

• in neurons: travel (propagate) along plasma membrane release of neurotransmitter

• in muscle fibers: action potentials cause the fiber to contract (shorten)

Action Potentials

• atrophy: decrease in size of cells decrease in size of organ

• hypertrophy: increase in size of a tissue because its cells enlarge w/out undergoing cell division

Medical Terminology