tissues honors anatomy & physiology chapter 4 human anatomy & physiology
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•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
•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
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
Connective Tissue
•most abundant & widely distributed of the 4 tissue types
•major functions:1. binding & supporting2. protecting3. insulating4. storing5. transporting
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
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 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
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
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
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
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
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
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