TissuesHonors Anatomy & PhysiologyChapter 4Human 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

1. Epithelial▫ from all 3 layers

2. Connective▫ mesoderm

3. Muscular▫ mesoderm

4. Nervous ▫ ectoderm

Embryology of Tissues

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

surrounding tissue cells▫type of connections between cells

Tissues

Classification of Tissues

1. Epithelial▫ covers body surfaces & lines

hollow organs, cavities, & ducts▫ forms glands

2. Connective 3. Muscle4. Nerve

Functions of Epithelial Tissues

•protection•absorption•filtration•excretion•secretion•sensory reception

Epithelial Tissue

•5 distinguishing characteristics1. polarity2. specialized contacts3. supported by CT (connective

tissue)4. avascular but innervated5. ability to regenerate

Polarity•apical & basal surfaces

▫differ in structure & function

•most apical surfaces contain microvilli, or cilia

•basal surface has thin supporting sheet called basal lamina▫selective filter▫scaffolding for cells to

migrate along

Specialized Contacts•epithelial cells form

continuous sheets ▫not glandular

epithelium▫lateral cell surfaces

see desmosomes & tight jcts (keeps things from diffusing between cells)

Supported by CT

•all epithelial sheets rest on CT

•reticular lamina: just below basal lamina

•basal lamina + reticular lamina = basement membrane

Avascular / Innervated

•epithelium contains NO blood vessels▫nutrients, O2 diffuse from underlying

CT vessels•has nerve fibers

Regeneration

•epithelial cells will reproduce rapidly when neighboring cells damaged or destroyed▫as long as necessary nutrients can

get to epithelium

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

pseudostratified 2. cell shape• squamous• cuboidal• columnar

Squamous Cells

•flattened, scalelike•protect

Cuboidal Cells

•boxlike, cubes•secretion, absorption

Columnar Cells

•tall, column shaped cells•secretion

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

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

substances

Simple Epithelium

Simple Squamous Epithelium

•cells flattened laterally•surface view: tiled floor•cross-section: fried egg•thin, permeable where rapid diffusion important▫Lungs▫Kidneys

Endothelium

•simple squamous epithelium that lines lymphatic and blood vessels and lines the cardiac atria and ventricles

•capillaries consist only of 1 endothelial cells thick (site of gas exchange)

Mesothelium

•epithelium found in serous membranes▫line ventral body cavities▫cover organs in ventral cavities

Simple Cuboidal Epithelium

•square cells with round, central nuclei in a sheet

•secretion•absorption•forms walls of small ducts of glands & kidney tubules

Simple Columnar Epithelium

•single layer, tall, closely packed cells•absorption•secretion•line digestive tract where cells have 2 modifications:

1. dense microvilli on apical surface2. glands that secret mucus (Goblet

cells)/intestinal juices

Pseudostratified Columnar Epithelium•cells vary in height•nuclei at variable heights•ciliated or nonciliated•all cells rest on BM (basement membrane) but not all reach free surface▫short cells replace tall ones if

damaged

Stratified Epithelium

•2 or more cell layers•cells are generated from below•more durable than simple epithelium•protection: major function•type of stratified epithelium determined by cell shape of top layer

Stratified Squamous Epithelium•found in areas subjected to wear and tear

▫upper layers rubbed away ▫lower cells replace

•top cells are squamous•as cells pushed up further from BM fewer nutrients reach them die lipids from atrophied cells add some water proofing

•keratinized/not keratinized▫keratin: tough protein

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

Stratified Cuboidal Epithelium

•rare•found in some ducts of larger glands

▫mammary glands, some sweat glands•2 layers of cuboidal cells

Stratified Columnar Epithelium•limited distribution in body

▫male urethra▫some glandular ducts▫@junction between 2 other types of

epithelial cells

Glandular Epithelium

•gland: 1 or more cells that make & secrete a product called a secretion

•secretions are aqueous solutions▫composition varies by gland

Secretion

•active process of gland releasing its product (also called secretion)

2 Classes of Glands

1. Endocrine glands (ductless glands)▫ internal secretion: cells exocytose

extracellular space capillaries target cells prompts some response in cell

▫ hormones: messenger chemicals2. Exocrine glands (glands with ducts)

▫ external secretion ▫ secrete product onto surfaces or into

body cavities

Types of Exocrine GlandsUnicellular Multicellular •Mucous cells &

Goblet cells•sprinkled thru GI

tract, respiratory tract

•2 parts:1. Duct 2. Secretory cells

▫ surrounded by CT forming fibrous capsule divides it into lobes

Types of Multicellular Exocrine GlandsUnicellular Multicellular

Connective Tissue

•most abundant & widely distributed of the 4 tissue types

•major functions:1. binding & supporting2. protecting3. insulating4. storing5. transporting

Classification of CT

•CT proper▫fat▫fibrous tissue

•cartilage•bone•blood

Characteristics of CT

•common origin▫mesenchyme

•degrees of vascularity▫cartilage: avascular▫dense CT poorly vascularized▫other types richly vascularized

•extracellular matrix▫few cells/ lots extracellular matrix

3 Main Elements in CT

1. ground substance2. fibers3. cells

• 1 + 2 = extracellular matrix• large variation in composition &

arrangement of the three large diversity of CTs each adapted to specific function

Ground Substance

•fills space between cells•contains fibers•function: molecular sieve•consists of

▫water▫interstitial fluid▫cell adhesion proteins (glue)

CT Fibers

•provide support•secreted by fibrocytes•3 types:

1. collagen2. elastic fibers3. reticular fibers

Collagen Fibers

•made of cross-linked protein collagen▫#1 protein in body▫very strong, high tensile strength

Elastic Fibers

•long, thin, branching fibers•made of protein: elastin•can be stretched return to original shape

•function: provide elasticity to tissues•found in: cartilage, skin, lungs, blood vessel walls

Reticular Fibers

•form delicate networks that surround small blood vessels& support soft tissue organs (liver, spleen)

•made of collagen derived protein•also found in BM of epithelium, around capillaries

CT Cells

•each class of CT has resident cell type:▫immature form –blast▫mature form - cyte

Loose CT

•3 types:1. Areolar2. Adipose3. Reticular

Areolar CT

•Functions:▫support & bind other tissues▫hold body fluids (reservoir of water &

salts)▫store nutrients

•Cells: all CT cells•Features: loose arrangement of fibers•Found: subcutaneous tissue

Adipose Tissue

•Functions: store triglycerides, insulation, protection

•Cells: adipocytes•Features: scant matrix, closely packed cells, rich blood supply

•Found: ass’c w/areolar CT, around heart, kidneys, lymph nodes

Adipose Tissue

•2 types:1. White: most adipose tissue 2. Brown: abundant mitochondria

▫ use fat to generate heat (less ATP, more heat)

▫ found on back of newborns: unable to shiver if chilled

Reticular Connective Tissue

•Function: reticular fibers form internal framework = stroma

•Cells: fibroblasts = reticulocytes•Features: only fibers are reticular•Found: lymph nodes, spleen, bone marrow

Dense CT

•3 types:1. Dense Regular2. Dense Irregular3. Elastic

Dense Regular CT

•Functions: resistance to tension•Cells: fibroblasts•Features: closely packed, parallel collagen fibers (parallel to direction of pull); appears white, flexible

•Found: tendons (muscle to bone) & most ligaments (bone to bone)

Cartilage •Function: withstands tension & compression•Cells: chondroblasts (lay down cartilage), chondrocytes found in lacunae

•Features: qualities intermediate between dense CT and bone, no nerve or blood supply, surrounded by perichondrium

•Found: ends of long bones, see next slide

Types of Cartilage

1. Hyaline2. Elastic3. Fibrocartilage

Hyaline Cartilage

•Function: provides flexibility & support

•Cells: chondrocytes in lacunae•Features: matrix appears glassy, most abundant type of cartilage,

•Found: embryonic skeleton, tips of nose, ends of long bones, connects ribs, to sternum, trachea, epiphyseal plates

Elastic Cartilage

•Function: maintains shape, strength and elasticity

•Cells: chondrocytes in lacunae•Features: very flexible•Found: pinna, epiglottis

Bone: Osseous Tissue

•Function: support and protect, cavities allow storage of fat and production of blood cells

•Cells: osteoblasts, osteocytes, osteoclasts

•Features: hard but some flexibility, more collagen than cartilage + inorganic calcium salts

•Found: skeletal system

Bone

•2 types:1. Compact Bone2. Spongy Bone

Compact Bone

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

•has 4 parts:1. Lamellae

▫ concentric rings of extracellular material & collagen

▫ make bone hard & strong2. Lacunae3. Canaliculi4. Central (haversian) canal)

Spongy Bone

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

trabeculae▫spaces between trabeculae filled with red

bone marrow

Blood

• 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

Muscle Tissue

•Function: movement, maintain posture, generate heat

•Cells: muscle fibers containing actin and myosin

•Features: contraction & relaxation•Found: skeletal system, walls of vessels and hollow organs, heart

Smooth Muscle

•Function: movement •Cells: 1 central nucleus, fusiform cells

•Features: involuntary & not striated, innervated by ANS,

•Found: walls of vessels & hollow organs, between hair follicles and dermis

Cardiac Muscle

•Function: propel blood thru body•Cells: branching with gap jcts = intercalated discs

•Features: striated, involuntary (ANS)•Found: only in wall of heart

Skeletal Muscle

•Function: move bones•Cells: multinucleated (peripherally located) muscle fibers

•Features: striated and voluntary•Found: attached to bones or skin

Nervous Tissue

•Function: regulate and control body functions

•Cells: neurons, neuroglial cells•Features: neurons can generate and/or respond to action potentials

•Found: nervous system

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

Mucosae (Mucous Membranes)•Function: absorption and secretion•Cells: stratified squamous epithelium or simple columnar epithelium, lie over CT layer = lamina propria

•Features: moist, most secrete mucus•Found: line all body cavities that open to outside body

Serosa (Serous Membranes)

•Function: lubrication •Cells: simple squamous epithelium (called mesothelium) on areolar CT

•Features: moist, squamous cells secrete thin watery serous fluid, serosa named according to organ: pleura, pericardium, peritoneum

•Found: closed ventral cavities

Tissue Repair

•3 phases:1. Inflammation2. Organization3. Regeneration/Fibrosis

Inflammation

•nonspecific reaction • injury causes tissue cells, macrophages,

mast cells inflammatory chemicals capillaries dilate & become more permeable neutrophils, monocytes & plasma fluid (clotting factors, abys) enter injured area form clot stops bleeding, holds wound together, isolating injured area giving some protection to infection scab forms

Inflammation

•Characterized by area of:•redness (rubor)•swelling •+/- pain (dolor)•warmth

Organization Phase of Tissue Repair

•begins during inflammatory pahse•blood clot replaced by granulation tissue:a friable, delicate tissue▫capillaries ▫fibroblasts collagen, growth factors

when phase complete become inactive or apoptosis

▫macrophages phagocytize injured cells/cell debris, clot

Organization Phase of Tissue Repair

Regeneration & Fibrosis Phase

•fibrous tissue beneath scab matures epithelium regenerate until it resembles surrounding skin

•+/- scar tissue

Injury Below Skin

•skin surface not breached•usually involves infection (pimple, sore throat)▫minor : heals by regeneration only▫more serious clot formation

possibly scarring

Scar Tissue

•permanent fibrous patch•if wound was extensive replaced only

with scar tissue does not replace function of normal tissue

•adhesions: scar tissue that forms around irritated organs in abdominopelvic cavity or w/in hollow organs

Healing in Different Tissues

•heal well: epithelium, areolar CT, dense irregular CT, bone, blood forming tissue

•moderate capacity to heal: smooth muscle, dense regular CT

•poor healing: skeletal muscle, cartilage•NO healing: cardiac muscle, nerve tissue

•https://www.dnalc.org/resources/3d/cellsignals.html