Primary Tissues: Structure and Function

• Study notes on primary tissues

Structure and Characteristics of Cells

• Biological hierarchy includes cells, tissues, organ systems, and organs based on cell specialization
• Cilia have a structure and function worth noting

Epithelium Synopsis and Characteristics

• There are three main types of epithelium
• Epithelium can be classified by cell shape and the number of cell layers
• Glandular epithelium is classified by cell number and secretion type
• Exocrine glands secrete via different methods that should be understood

Connective Tissue Synopsis and Characteristics

• Know five functions of connective tissue
• Know how to classify connective tissue based on its structure

Nerve Tissue

• Nerve tissue cells can be classified by function
• Neurons have a structure
• Neurons conduct impulses using different directions
• The nervous system has anatomical classifications
• Key elements comprise the central nervous system
• Neuroglial cells possess functions
• Muscles have a nomenclature of features

Muscle Tissue

• Muscle tissue can be classified based on structure
• Skeletal muscles have a microscopic structure
• Muscles act together as stabilizers, agonists, antagonists, and synergists, which can be exemplified

Tissues

• Tissues constitute aggregates of cells performing a specific function
• Organization permits function
• Four Tissue types: epithelium, connective, muscle, and nervous
• Epithelium covers body surfaces, cavities, and glands
• Connective tissue structurally and functionally supports other tissues
• Muscle tissue contains contractile cells for movement
• Nervous tissue's purpose is to receive and transmit impulses based on stimuli

Epithelium

• Cells form cohesive sheets that line external surfaces or cavities
• Sheets can be layered but are tightly joined by junctions
• The sheets are supported by a basement membrane on the basal surface
• The apical surface is opposite the basal surface

Epithelium Types & Functions

• Surface epithelia provides a covering
• Glandular epithelia facilitates secretion
• Provides protection like a skin barrier
• Secretion, forming glands
• Intestines facilitate absorption

Surface Epithelium Classification

• Classification is based on cell shape, number of layers, and presence of special features
• Squamous cells are flattened with an elongated nucleus
• Cuboidal cells feature a round nucleus centrally placed
• Columnar cells possess an oval nucleus basally situated

Epithelium Layers

• Simple epithelium has one cell layer
• Stratified epithelium has two or more layers
• Transitional epithelium is a combination of two cell shapes
• Pseudostratified epithelium appears simple, but not all cells reach the free surface

Epithelium Special Features

• Special features occur on the apical surface of epithelia
• Keratin is located on the epithelial surface of skin and nails and withstands abrasion
• Cilia are motile cytoplasmic processes that help move fluid or particles, such as in the respiratory system.
• Microvilli are finger-like projections that increase surface area like the brush-border in the digestive system
• Stereocilia are long microvilli found in the middle ear and epididymis

Glandular Epithelia

• Glandular epithelia derive from epithelia
• Glandular epithelia are classified as endocrine or exocrine
• Endocrine glands internally secrete products from the basal surface
• Exocrine glands externally secrete products from the apical surface

Endocrine Glands

• Endocrine Glands secrete directly into the bloodstream without ducts
• Hormones exemplify endocrine gland products

Exocrine Glands

• Exocrine glands release products via ducts
• Exocrine gland classification includes morphology and secretion mechanism
• Morphology of exocrine glands includes simple or compound structures
• Secretion mechanisms include Merocrine, Apocrine, and Holocrine

Exocrine Secretion

• Merocrine involves secretion via exocytosis
• Apocrine involves the discharge of free, membrane-bound vesicles
• Holocrine involves the discharge of whole secretory cells

Connective Tissue

• Tissue provides general structure, mechanical strength, and support
• Classification relies on its components
• Support cells, types of cell
• Extracellular matrix, ground substance and fibers

Components of Connective Tissue

• Includes Cells + ECM (GS+F)

Connective Tissue Components

• ECM includes ground substance and fibers
• Cells include Fibroblasts, Chondroblasts, Adipocytes, Stem cells, Macrophages, and Mast cells
• Ground substance: Glycoprotein and Carbohydrates make transparent material
• Fibers: Collagen, Reticular and Elastic

Connective Tissue Fibers

• Tissue function hinges on organization and amount
• There are three main types of fibers
• Collagen fibers, elastic fibers, and reticular fibers
• Fibroblast support cells primarily produce each of these fibers

Collagen

• Fiber type is most abundant
• Flexible with high tensile strength
• Collagen fibers consist of more than one type of collagen molecule, like Type I or II
• Reticular fibers form a framework for tissues and organs

Elastic

• Fibers are composed of elastin protein bundles
• Respond to stretch
• Interwoven with collagen to limit distensibility

Connective Tissue Cells

• Fibroblasts
• Myofibroblast
• Chondroblast
• Osteoblasts
• Adipocytes

Fibroblasts

• Typically spindle shaped cells with a flattened, large ovoid nucleus
• Exists in active “fibroblast” or inactive “fibrocytes” states
• Secretes, maintains, and recycles the extracellular matrix by synthesizing fibers and secreting components of ground substance

Myofibroblasts

• Functions include synthesizing and secreting CT fibers
• Active fibroblast
• Associated with repair
• Contraction

Chondroblasts

• Round cells surrounded by a lacunae
• Chondroblast cells are active, whereas Chondrocytes are inactive
• Functions to secrete the extracellular matrix components of cartilage

Osteoblasts

• Osteoblasts are the active form
• Osteocytes are the inactive form
• Functions to secrete the extracellular matrix components of bond

Adipocytes

• Large lipid-filled cells with a flattened stained nucleus
• Adipocytes are inactive, whereas lipoblasts are active
• Stores lipids and energy
• Cushions and insulates skin and other organs

Connective Tissue Classification

Loose CT

• Abundant ground substances.
• Mixed random orientation fibers.
• Numerous cell types.
• Functions in diffusion/immune response.
• Located underneath epithelia and around blood vessels.

Dense Irregular CT

• Less ground substance (comparatively)
• Primarily collagen
• Multi directional orientation
• Functions to provide resistance by stretching in multiple directions
• Located underneath epithelia and found in the submucosa of certain organs and dermis of skin.

Dense Regular CT

• Very little ground substance
• Primarily collagen
• Regular unidirectional fibres
• Functions to provide resistance when stretched in one direction
• Located in Tendons

Cartilage Type II

• Consists of chondroblasts and chondrocytes
• Extracellular ground substance.
• Contains Collagen II
• It’s types include Hyaline Elastic and Fibrocartilage

Types of Cartilage

Hyaline

• Contains Collagen II + GS that function in development with respiratory passages

Fibrocartilage

• Contains Type I & II collagen + GS
• Located in IV discs and joints

Elastic

• Contains Type II collogen and elastic fibers and GS
• Found in the external ear and larynx

Bone

• The ECM is mineralized, providing support and protection
• Osteoblasts produce the ECM (osteoid) + Collagen type I
• Osteoclasts reabsorb bone

Bone Cells

• Osteoblasts stain dark in the periphery.
• Surrounded by osteoid, osteocytes have a stellate shape

Adipose Tissue

• Contains Lipoblast and Adipocytes
• Located throughout loose connective tissue

Muscles

• Movement comes from specialized cells by actin + myosin proteins
• Myofibroblasts contract and secrete collagen, located in an area of healing .
• Pericytes are smooth cells around blood vessels
• Myoepithelial cells line secretory glands
• Includes, skeletal, caridac, and smooth muscles

Skeletal Muscle

• It is a ( voluntary) muscle that provides conscious movement
• The muscles have visible cross-striations and multiple nuclei
• Forms muslces of skeleton, eyes, and tongue

Smooth Muscle

• It contains involuntary muscle that functions through an autonomic nervous system
• No striations are present
• spindle shaped
• the single nucleus islocated centrally
• Located on the GIT, blood vessels, and urogenital organs

Cardiac Muscle

Involuntary muscle through the autonomic system

• Straited, fibers are branched
• Joined with Intercalated discs
• Located in the heart

Nerves

• Nervous System controls all bodies functions via electricle signals
• System transmits neurons from brain to the body , vice versa. Includes the CNS and PNS which are split depending on structre.
• Sensory /motor - all body parts except viscera/ and smooth muscle tissue.

Nervous System - Structure

• Includes CNS (Brain and spinal cord) and PNS (cranial spinal -perioheral nerves)
• Components include motor / and sensory compontents. + cell bodies (Ganglia)
• SNS (Somatic parts) & PNS which sensory/motor parts with muscle tissue
• ANS (Autonomic parts) Includes parts such as heart or glands. symapthetic or parasymathetic division

Nervous Tissue

• Composed of nerve cells (neurons)
• The impulse response is what stimulates transmission.
• The support cells (known as neuroglia) do not stimulate conduction

The Neuron

• Sensory neurons transport to the CNS using pain -temp -touch responses
• Has motor nerouns in CNS via impulses and involuntary activity

Neuron

Cell Body

• Made of organelles, nucleus -Nissl substance and Axon hollock
• Dendrite
• Axon

Axons

The job is to trasnmit pulses “away” that allow Synatic junctions to transmit signals

Neuron : Structures

• Unipolar (sensory)
• Bipolar (special sensory )
• Multipolar functions in somatic functions
• Pseudounipoloar aids in Sensory

Neroun : Function

There are various functions

• Sensory Afferent relays information from recptors.
• interneurons functions in the neroun to help networl.
• Motor (Efferent)

Neurgolia

There function aid Neuron such as

• ASTROCYTES-metabolic transfer with blood, this homeostasis
• PNS satilate cells and provides structure

PNS :

• Uses Nerves via axons for Motor or Sensory It is connected using support tissue
• Is either Myelinated or non Mylenated
• Structurally : Is bundle that connects Nerves fiber
• It is a trunk bind
• Surrounds axones to promote formation
• it transfers impulses via
• Presynaptic to Postsynaptic

Ganglion

• The Ganglion contains a ganglia
• Nerve collection has support cells