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BLGY1115 > Tissues > Flashcards

Tissues Flashcards

1
Q

Histology

Definition

A

the study of the tissues and their normal structure

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2
Q

Tissue

Definition

A
  • a group of cells with similar structure and function
  • 4 types:
  • epithelia
  • connective
  • muscle
  • nervous
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3
Q

Origin of Tissues

A
  • the cells that make up the different tissue types are made up of cells from the three different sections of the primary germ layer:
  • ectoderm
  • mesoderm
  • endoderm
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4
Q

Epithelial Tissues

Origin

A

Ectoderm
Mesoderm
Endoderm

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5
Q

Epithelial Tissues

Function

A
  • Cover Surfaces
  • external, exposed to stuff from the outside environment
  • internal, exposed to inner cavities
  • Form Glands, secretory structures
  • Physical Protection, from abrasion, dehydration, chemical & biological damage
  • Absorption and Excretion, controlled permeability
  • Sensation
  • Specialised Secretion, gland cells
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6
Q

How do epithelial tissues protect against abrasion?

A
  • keratinisation
  • some epithelial cells produce keratin forming calluses
  • keratin production increases at sites that receive more abrasion
  • this can happen internally in herbivores
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7
Q

Epithelial Tissues

Characteristics

A
  • cells are closely bound forming sheets
  • Cell Polarity, different apical and basal surfaces of cells and uneven distribution of organelles
  • Attachment, almost always situated on top of connective tissue
  • Avascularity, no blood vessels get all nutrients by diffusion from the intercellular fluid
  • Regeneration, short half life
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8
Q 
Epithelial Tissues
Apical Specialisation (Polarity)
A
  • Microvilli, increase surface area and aid motility
  • Cilia, longer than microvilli and more motile, move fluids across the epithelial surface
  • Stereocilia, long and non-motile
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9
Q 
Epithelial Tissues
Maintaining Integrity (cellularity)
A
  • Intercellular Connections, tight junctions & desmosmomes & gap junctions
  • Connetion with Body, basement membrane (CAMs)
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10
Q

Types of Epithelia

Classification

A
  • LAYERING
  • Simple, a single fragile layer of cells
  • Stratified, several layers of cells, tough
  • CELL SHAPE
  • Squamous, thin fat irregular shape nuceli near thickest part of cell
  • Cuboidal, hexagonal square shaped with central nuclei
  • Columnar, hexagonal rectangular shaped nuclei near basal surface
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11
Q

Epithelial Tissues

Simple Squamous

A
  • most delicate
  • found where absorption and slippery surfaces required
  • kept moist by intestinal fluid
  • e.g. lungs
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12
Q

Epithelial Tissues

Stratified Squamous

A
  • tough
  • physical and chemical protection
  • keratinised can withstand stress and dehydration
  • e.g. skin surface, oral cavity of domestic animals
  • non-keratinised must be kept moist
  • e.g. oral cavity of humans, pharynx, oesophagus
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13
Q

Epithelial Tissues

Simple Cuboidal

A
  • limited protection
  • secretion and absorption
  • e.g. glands, ducts ,kidney tubules
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14
Q

Epithelial Tissues

Stratified Cuboidal

A
  • rare
  • secretion
  • e.g. ducts of sweat and mammary glands
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15
Q

Epithelial Tissues

Transitional Cuboidal

A
  • covers surfaces that expand and contract
  • so shape of cells changes making them difficult to classified
  • permit expansion and recoil
  • e.g. bladder
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16
Q

Epithelial Tissues

Simple Columnar

A
  • protection, secretion, absorption

- e.g. lining of stomach, intestines and uterus (endometrium)

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17
Q

Epithelial Tissues

Pseudostratified Columnar

A
  • appears stratified but is simple
  • typically possesses cilia
  • protection and secretion
  • e.g. nasal cavity, trachea, bronchi
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18
Q

Epithelial Tissues

Stratified Columnar

A
  • rare
  • protection
  • e.g. pharynx, epiglottis, salivary gland ducts
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19
Q

Glandular Epithelia

A

–many epithelia contain gland cells

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20
Q

Epithelial Tissues

Gland Structure

A
  • Unicellular, e.g. goblet cells, trachea, intestines

- Multicellular, e.g. salivary, pancreas, sweat, mammary

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21
Q

Epithelial Tissues

Gland Cells - Endocrine

A
  • secrete hormones into surrounding fluid which then diffuse into blood
  • maybe part of epithelial surfaces or maybe separate
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22
Q

Epithelial Tissues

Gland Cells - Exocrine

A
  • secreted via ducts
  • Serous Glands - watery secretions and enzymes
  • Mucous Glands - mucins which are glycoproteins that become mucus when hydrated
  • Sebaceous Glands - oil glands, lipid producy
  • Mixed Glands - serous and mucous
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23
Q

Modes of Exocrine Secretion

A

Merocrine - secretory product stored in vesicles and released by exocytosis
Apocrine - secretory vesicles collect in apical side of cell and the top part of the cell is shed releasing the products, the cell then regrows
Holocrine - whole cell becomes packed with secretory vesicles then ruptures releasing contents, cells have to be replaced from stem cells

24
Q

Connective Tissue

Origin

A
  • mesoderm

- ectoderm

25
Q

Connective Tissue

Functions

A
  • structural framework
  • transporting fluids
  • protection & support
  • interconnective tissue
26
Q

Connective Tissue

Charcteristics

A
  • specialised cells
  • matrix surrounding cells composed of protein fibres and ground substance (fluid)
  • never exposed to the external environment
  • usually highly vascularised (except cartilage)
  • contains sensory cells
27
Q

Connective Tissues

Types

A

Connective Tissue Proper
Fluid Connective Tissue
Supporting Connective Tissue

28
Q

Connective Tissue

Proper

A
  • packing tissue
  • most diverse range of cells
  • extracellular fibres in a ‘syrupy’ ground substance
29
Q

Connective Tissue

Proper - Cells

A
  • Fibroblasts - always present they secrete polysaccharides and proteins, proteins become roteoglycans and extra cellular fibres
  • Adipocytes - storage of energy
  • Mesenchymal Cells - undifferentiated embryonic stem cells
  • Defence Cells - e.g. lymphocytes and macrophages
30
Q

Connective Tissue

Proper - Matrix

A
  • produced from proteins secreted by fibroblasts
  • three types of fibre:
  • Collagen - most common, long straight unbranched fibres
  • Reticular Fibres - branched interwoven network that supports position of blood vessels
  • Elastic Fibres - contain the protein elastin, branched and wavy
  • Ground Substance - clear, viscous and colourless
31
Q

Connective Tissue Proper

Loose Connective Tissue

A
  • packaging fills spaces providing cushioning and support
  • least specialised
  • ground substance makes up most of volume
  • fibres loosely organised
  • highly vascularised and help to supply nearby epithelia
  • usually underlies epithelia, fibroblasts contribute to the composition of the basement membrane
32
Q

Connective Tissue Proper

Adipose Tissue

A

-adipocytes make up most of volume
-insulates and cushions
-energy storage
-endocrine role
-two types:
White - contain lots of lipid droplets that coalesce taking up most of cell volume pushing the cytoplasm to one side
Brown - highly vascularised
-more mitochondria
-usually found in young or hibernating animals
-generates heat by non-shivering thermogenesis
-thermogenin protein in inner mitochondrial membrane allows leakage of protons making respiration less efficient and releasing more heat

33
Q

Connective Tissue

Fluid Connective Tissue

A
  • distinctive cell population and proteins

- under normal conditions proteins are suspended in the ground substance they do not form insoluble fibres

34
Q

Connective Tissue

Fluid Connective Tissue - Blood

A
  • -erythrocytes - for gas transport at least half of volume
  • -leukocytes - immunity:
  • macrophages, engulf foreign bodies
  • microphages, engulf foreign bodies
  • lymphocytes, antibody production
  • basophils, contain histamine which drives local inflammation when released
  • -erythrocytes and leukocytes are formed in bone marrow from haemocytoblasts
  • -thrombocytes - packages of cytoplasm that contain proteins, they form clots
  • formed from megakaryocytes in bone marrow
  • -ground substance is plasma
35
Q

Connective Tissue

Fluid Connective Tissue - Lymph

A

-lymphocytes
-largely interstitial fluid
transports absorbed fats

36
Q

Connective Tissues

Supporting Connective Tissue

A
  • less diverse cell population
  • majority of matrix is tightly packed fibres
  • very little ground substance
  • two types: Cartilage and Bone
37
Q

Connective Tissue

Supporting Connective Tissue - Cartilage

A
  • -cells called chondrocytes that live in pockets called lacunae
  • -matrix made up of a firm gel of proteoglycans and collagen & elastin fibres
  • -avascular
  • -3 types:
  • Hyaline - in joints, reduces friction between bones
  • Elastic - higher proportion of elastin provides support
  • Fibrocartilage - similar to hyaline as it reduces friction but also resists compression
38
Q

Connective Tissue

Supporting Connective Tissue - Bone

A
  • -cells called osteocytes arranged around blood vessels, communicate via cytoplasmic extensions that run through passageways in the matrix called canaliculi
  • -matrix is calcified, very little ground substance, 1/3 collagen fibres, 2/3 mixture of calcium salts
39
Q

What are the tissue types that compose membranes?

A

epithelia and connective tissue

40
Q

What are the four types of membranes?

A
  • mucous (mucosa)
  • serous
  • cutaneous
  • synovial
41
Q

Membranes

Mucous / Mucosa

A
  • lines internal cavities that communicate with the external environment
  • kept moist at all times by secretion from goblet cells OR exposure to fluid
  • usually simple epithelia (secretory or absorptive function) underlying loose connective tissue layer
  • connected by a basement membrane
  • loose connective tissue layer is called the lamina propria
42
Q

Membranes

Serous

A
  • lines internal cavities that don’t interact with the external environment
  • mesothelium (simple squamous epithelium) on layer of loose connective tissue
  • very thin
  • prevents internal organ from rubbing against the walls of the body
  • no secretion, allows tissue fluid to diffuse onto surface instead
43
Q

Membranes

Cutaneous

A
  • three layers

- stratified squamous epithelium on loose connective tissue on dense connective tissue

44
Q

Membranes

Synovial

A
  • lines joint cavities
  • ‘epithelium’ consisting of an incomplete layer of squamous or cuboidal cells
  • no basement membrane
  • on layer of specialised loose connective tissue
45
Q

Muscle Tissue

Origin

A

mesoderm

46
Q

Muscle Tissue

Characteristics

A
  • contain myofibrils, actin and myosin

- specialised for contraction

47
Q

Muscle Tissue

Function

A
  • movement
  • support of soft tissue
  • maintain posture
  • guards entrances and exits
  • maintains body temperature
48
Q

Muscle Tissue

Types

A
  • three types with same contraction mechanism but different structure:
  • skeletal
  • cardiac
  • smooth
49
Q

Muscle Tissue

Skeletal

A
  • striated
  • voluntary
  • attached to skeleton via tendons
  • most basic cells are myoblasts (mononucleate)
  • myoblasts fuse together forming multinucleate cells called myotubes
  • once myotubes synthesise and become packed with actin and myosin they are called muscle fibres or myocytes
  • actin and myosin arranged into sarcomere units that arrange longitudinally to form myofibrils that give skeletal muscle its striated appearance
  • satellite cells are stem cells enclosed in the basement membrane which surrounds the muscle fibre, normally they fuse with existing fibres
50
Q

Muscle Tissue

Cardiac Muscle

A
  • striated
  • involuntary
  • only found in the heart
  • cardiocytes are smaller than skeletal muscle cells and usually mononucleate
  • myofilaments arranged in the same way as in skeletal muscle giving cardiac muscle its striated appearance
  • cardiocytes are extensively interconnected by desmosomes and gap junctions
  • no satellite cells so damage cannot be repaired
  • rhythmic contractions controlled by pacemaker cells that are regulated by the autonomic nervous system
51
Q

Muscle Tissue

Smooth Muscle

A
  • not striated
  • involuntary
  • found in blood vessels, digestive & reproductive tracts and the urinary bladder
  • spindle shaped, mononucleate cells
  • can divide and repair
  • actin and myosin are not arranged uniformly so smooth muscle does not appear striated
  • can initiate contraction on their own via pacemaker cells, gap junctions coordinate contractions between cells and is regulated by the autonomic nervous system OR contraction is controlled only by the autonomic nervous system e.g. iris
52
Q

Neural Tissue

Origin

A

ectoderm

53
Q

Neural Tissue

Function

A

conduction of electrical impulses or action potentials

54
Q

Neural Tissue

Location

A
  • 98% of neural tissue is found in the brain and spinal cord in the central nervous system
  • the rest is found in the peripheral nervous system in afferent (to CNS) and efferent nerves (away from CNS)
55
Q

Neural Tissue

Categories of Efferent Nerves

A
  • -SOMATIC, voluntary and involuntary reflexes
  • -AUTONOMIC:
  • Sympathetic, fight/flight response, (adrenaline, noradrenaline -> adrenergic receptor)
  • Parasympathetic, (acetylcholine -> cholinergenic receptors)
56
Q

Neural Tissue

Cell Types

A
  • Neuroglia, provide supporting framework for tissue, regulate nutrient supply, assist in tissue repair e.g. schwann cells
  • Neurones, cell body=soma, dendrites bring information to the cell, convey information via propagation of electrical impulses along the axon
  • ganglion is a grouping of cell bodies
  • plexus is a branching of neural cells

BLGY1115 (10 decks)

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