Class 3 - BIPN Midterm

Tissue types

Epithelial Tissue

• COVERS all body surfaces

• large sheets of cells

• Lines body cavities, internal organs

• Makes up glands

Connective Tissue

• SUPPORTS

• Binds, supports, protects tissues

Muscle Tissue

• MOVES

• Moves skeleton and organ walls

Nervous Tissue

• CONTROLS

• regulates all tissues

• processes information

Histology

• Study of tissue structure on microscopic level

  • 2D slices of a 3D object

• obtain tissues via Biopsy

• diagnose diseases

Histology: Sample Preparation

1. Fixation: preserve tissue via paraformaldehyde

2. Sectioning: cut tissue into thin slices (um)

3. Staining: contrast btw structures, H&E stain

Epithelia Properties

1. Densely packed sheet of cells: NO ECM between them

2. Cells supported by underlying CT: anchored via BM

3. Cells have polarity: apical and basal (BM) surfaces

4. Avascular: gases diffuse up into epi

5. Constant regeneration/turnover

Cell Junctions

• anchors epithelial cells to one another

• barrier to diffusion

• allows molecules to pass cytosol-to-cytosol

1. Tight Junctions: anchors cells, diffusion barrier, leak proof

2. Desmosome: anchors cells to resist stress/stretching

3. Gap Junctions: protein channels btw cells, ion flow

Hemidesmosome

• cell junction connecting Epithelia to BM

Epithelia Classification

1. Number of layers (simple, strat.)

2. Cell Shape (squamous, cuboidal)

3. Cell specialization (cilia, microvili)

Simple Squamous

• fast diffusion, filtration

• e.g. Alveoli, blood vessels (endothelial), serous membranes (mesothelial)

Simple Cuboidal

• secretion, absorption

• e.g. Kidney tubules, most exocrine glands

Simple Columnar

• secretion, absorption, make secretions

• e.g. GI tract

  • microvilli increase SA

  • goblet cells secrete mucus

Stratified Squamous

• protection from abrasion

• e.g. Skin

  • keratinized: dry, water resistant, UV protection

• e.g. Vag, anus

  • non-keratinized: moist

Pseudostratified Columnar Epithelium

• all cells TOUCH BM

• protection, secretion, movement of substances

• e.g. respiratory tract, trachea

  • Cilia: movement of mucus

Glands

• cell/organ that secretes a chemical substance

• Unicellular: Goblet Cells

  • cells found in non-secretory organs: SI

• Multicellular: sweat glands, pituitary glands

  • organs themselves whose main function is secretory

  • exocrine, endocrine

Exocrine Glands

• secrete contents into a DUCT

• e.g. sweat glands

Endocrine Glands

• NO DUCT

• secrete contents directly into extracellular space/blood

• e.g. Pituitary gland

Connective Tissue Properties

• ECM: ground substance and protein fibers

• sparse (specialized) cells

  • -blast: immature, synthesizes ECM

  • -cyte: mature, maintains/repairs ECM

Ground Substance

• ECM component

• unstructured material filling btw cells

• holds all interstitial/extracellular fluid

Protein Fibers

• ECM component, mechanical support

• Collagen:

  • tensile strength (resist tearing from stretch)

• Elastic:

  • stretch and recoil

CT Classifications

1. CTP: fibroblasts

2. Cartilage: chondrocytes

3. Bone: osteocytes

4. Blood: blood cells

CTP: Cell Types

• Fibroblasts: produce ECM (collagen, elastin)

• Fibrocytes: maintain ECM

• Adipocytes: fat storage

• Macrophages: engulf pathogens/dead cells

• Mast cells: inflammatory response

Connective Tissue: CTP

• Loose CTP:

  • Areolar

  • adipose

  • reticular

• Dense CTP:

  • regular

  • irregular

  • elastic

Loose CTP

• Areolar:

  • filler tissue btw organs

  • under MOST epithelia/organs

  • Fibroblasts, elastic and collagen fibers

• Adipose:

  • Energy(fat) storage

  • subcutaneous layer/around organs

  • Adipocytes, collagen

Dense CTP

• Regular: sleek waves

  • collagen fibers ALIGNED

  • tensile strength

  • tendons, ligaments

• Irregular: marbled

  • collagen fibers UNALIGNED

  • strength in ALL DIRECTIONS

  • skin, cover muscles/nerves

• Elastic: hairtie squigle

  • elastic fibers

  • stretch and recoil

  • artery walls, stretchable organs

Connective Tissue: Cartilage

*Shock absorber

*ALL HAVE: Chondrocytes in lacunae

• Hyaline:

  • most abundant

  • synovial joints, tip of nose

• Elastic:

  • mechanical support, shape retention

  • external ear

• Fibrocartilage:

  • Strong shock absorber

  • intervertebral disks

Cartilage: Cell Types

• Chondroblasts: secrete ECM

• Chondrocytes: maintain ECM

• avascular

• stronger collagen, MORE ground substance

  • strong, effective shock absorber

Loose CTP v Cartilage

Loose CTP:

• fluffier, soft, flexible

• many loose fibers

Cartilage:

• firmer, resistant to compression

• LESS fibrous, more ground substance

Elastic CT v Elastic Cartilage

Elastic CT:

• Fibroblasts

• minimal collagen

• MORE PREVALENT

• arterial walls

Elastic Cartilage:

• chondrocytes

• more + stronger collagen

• ears

Bone

• connective tissue for protection

• osteoblasts, osteocytes in lacunae

• ECM has collagen + minerals

• highly vascularized

• Concentric rings

Blood

• Nutrient and O2 transport

• immune defense

• Erythrocytes, leukocytes

• Plasma: liquid ground substance

Muscle Types

• Skeletal

  • voluntary contractions, attached to bones, movement

• Cardiac

  • heart muscle, blood pumping

• Smooth

  • blood vessels, internal organs

  • GI contraction, bv diameter, uterine contractions

Body Membranes

1. Cutaneous (skin, dry)

2. Mucosa (lines cavities OPEN to external environment)

3. Serosa (lines cavities CLOSED to external environment)