Tissues Study Guide

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What are the 5 stages of pre-embryonic development?

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Biology

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1

What are the 5 stages of pre-embryonic development?

Fertilization, cleavage, blastocyst stage, implantation, gastrulation

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2

What happens in fertilization?

the paternal and maternal chromosomes fuse to form a zygote, moves down the uterine tube and goes through rounds of mitosis and cytokinesis, implants in uterine tube

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3

What happens in cleavage?

period of rapid mitotic cell division, blastomeres are produced, relative size the same, daughter cells become smaller, solid mass of cells called a morula is made

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4

What happens in the blastocyst stage?

morula with 32 cells has entered the uterus, blastomeres inside secrete enzymes that break down the zona pellucida, morula now becomes a blastocyst at the end of day 4, mitotic divisions continue, differentiates into trophoblast and inner cell mass

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5

What happens in implantation?

Trophoblast cells secrete enzymes that break down the zona pellucida & allow blastocyst to hatch, blastocyst then floats free in uterine cavity until day 6, trophoblast cells adhere to the endometrium and embeds in uterine wall, trophoblast cells proliferate and form 2 layers, hCG begins to be secreted by trophoblast cells, inner cell mass undergoes change and becomes bilaminar embryonic disc

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6

What two distinct layers are formed when trophoblast cells proliferate?

Cellular (inner) and syncytial (outer) trophoblast

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7

What makes up the bilaminar embryonic disc?

hypoblast (deeper layer) and epiblast (superficial layer)

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8

What day is implantation complete?

day 11

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9

When implantation is complete, what two structures form?

amniotic sac and yolk sac

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10

What happens in gastrulation?

changes begin and primary germ layers form, bilaminar disc elongates and broadens at anterior end and a primitive streak appears on dorsal surface, third germ cell layer develops and the bilaminar embryonic disc transforms into a three-layered embryo

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11

What are the three layers in the three-layered embryo?

endoderm, ectoderm, mesoderm

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12

What is a blastomere?

identical cells formed by cleavage divisions

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13

What does a blastomere do?

secrete enzymes that break down the zona pellucida and allows the blastocyst to hatch

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14

What is a blastocyst?

a hollow ball of cells with a cluster of cells inside known as the inner cell mass

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15

What is a morula?

solid ball of blastomeres surrounded by zona pellucida

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16

What are the two distinct cellular components of a blastocyst?

Trophoblast and inner cell mass

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17

What is the function of the trophoblast?

Adheres to, digests, and implants in the endometrium, protects the conceptus from attack by the mother's immune cells

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18

What role does the hCG play in sustaining pregnancy?

Maintains hormone production by the corpus luteum, preventing menses, helps prevent the mother's immune system from rejecting the implanted embryo

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19

How has knowledge of the hCG hormone become clinicaly and commercially useful?

hCG in a women's blood or urine is what is detected in pregnancy tests

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20

From what embryonic structure does the bilaminar embryonic disk originate?

Inner cell mass

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21

What are the three primary germ layers?

endoderm, mesoderm, ectoderm

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22

What is the endoderm?

the internal germ layer that lines the digestive, respiratory and urogenital systems and the glands associated with these systems

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23

Which germ layer enters the primitive streak?

Endoderm

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24

What is the mesoderm?

the middle layer between ectoderm and endoderm

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25

What two structures are in the mesoderm?

mesenchyme and notochord

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26

What is the notochord?

a flexible rod that provides stable support for embryo

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27

What is the ectoderm?

outer layer at dorsal side of embryonic disc

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28

Examples of ectoderm

structures of the nervous system and the skin epidermis

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29

The endoderm, mesoderm, and ectoderm are all considered....

epithelia

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30

What are the four extraembryonic membranes?

amnion, chorion, yolk sac, and allantois

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31

What is the amnion?

a thin but tough sac of membrane that covers an embryo, surrounds the amniotic cavity

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32

What does the amnion do?

Provides a buoyant environment that protects the developing embryo against physical trauma and helps maintain a constant temperature

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33

Amnion is also called?

bag of waters

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34

What is the yolk sac?

endoderm-lined membrane that receives nourishment from the endometrium, forms part of the gut

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35

All the body organs derive from the primary germ layers. True or False?

True

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36

The yolk sac is the source of the....

earliest blood cells

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37

What is the allantois?

membrane sac that stores waste and is the site for gas exchange, delivers oxygen to embryo, structural base for the umbilical cord that links embryo to the placenta

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38

What is the chorion?

outer membrane that surrounds the amnion and the embryo, develops fingerlike chorionic villi, formed by the trophoblast and the extraembryonic mesoderm

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39

What is the function of the chorion?

helps in the exchange of nutrients, gases, and wastes between the embryo and the mother's body, protects and nurtures the embryo

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40

What is a tissue?

groups of similar cells which are specialized to perform a specific function

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41

What are the 4 basic types of tissue?

epithelial, connective, muscle, nervous

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42

What does epithelial tissue do?

form boundaries between different environments, lines body cavities, forms glands, covers exposed body surfaces, forms boundaries between different environments

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43

Example of epithelial tissue

lining of digestive tract and other hollow organs

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44

What does connective tissue do?

supports, protects, binds other tissues together, fills internal spaces

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45

Connective tissue is a ________________ support to organs

structural

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46

Examples of structures that have/are connective tissue

Bones, tendons, fat

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47

What does muscle do?

contracts to cause movement, generates heat used to maintain core body temperature

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48

Examples of muscles

skeletal, cardiac, smooth

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49

What does nervous tissue do?

carries information from one part of the body to another through electrical impulses (internal communication)

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50

Examples of nervous tissue

brain, spinal cord, nerves

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51

What 3 general features tend to anchor cells together and stabilize tissues?

glycoproteins on cell surface, basement membrane, intercellular junctions

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52

Glycoproteins on cell surface help anchor cells to....

one another

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53

Basement membrane helps anchor cells to...

connective tissue

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54

Intercellular junctions are ______________________ in the membrane

specializations

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55

Name the 5 common types of cellular junctions

tight junctions, adherens junctions, desmosomes, hemidesmosomes, gap junctions

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56

Describe tight junctions

the fusion of transmembrane proteins of adjacent cells in the intercellular space that circle the entire cell

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57

What do tight junctions do?

helps cells adhere to all surrounding cell, prevents leakage of extracellular fluid, doesn't allow any space between adjacent cells

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58

What are adherens junctions?

a dense protein layer of proteins on the inside of the plasma membrane that attaches both to membrane proteins and to cytoskeletal proteins

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59

Which junction has a long, extended plaque?

adherens junction

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60

In adherens junctions...

cadherins attach intracellularly to a plaque and extends through the plasma membrane and attach to cadherins from an adjacent cell

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61

In adherens junctions, there are _______________ _______ that hold cells together so ET can be a strong membrane barrier

adhesion belts

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62

What are desmosomes?

button shape plaque under plasma membrane with intermediate filaments extending through cytoplasm and attaching to desmosome on opposite side of cell

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63

Desmosomes have...

cadherins

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64

Desmosomes resist pulling of tissue which creates internal _______________ in tissue

strength

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65

Desmosomes are common in ____________ & ____________ muscle and _______________

cardiac; smooth; skin

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66

Hemidesmosomes are common in what tissue?

epithelial

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67

The plaque of hemidesmosomes have...

transmembrane integrin proteins inserted, integrins attaching to laminins on outside of cell, and intermediate filaments

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68

What do integrins do in hemidesmosomes?

anchor to plaque and extend through the membrane nd anchor proteins in basement membrane

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69

What do intermediate filaments provide?

strength and stability to tissue

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70

What are gap junctions?

communicating junctions where adjacent cells are close together

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71

Gap junctions contain ___________ in the plasma membrane which form hollow cylinders called _________________

connexins; connexons

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72

What do gap junctions do?

allow passage of chemical substances like solutes between cells, allow ion flow to synchronize activity in cells

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73

What are the two major categories of epithelial tissue?

covering and lining epithelium, glandular epithelium

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74

What are some special characteristics of ET that distinguish it from other tissues?

high degree of cellularity, specialized cellular/lateral contacts, polarity, avascularity, presence of a basement membrane, has a nerve supply, high regenerative capability

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75

What type of specialized lateral contacts are common in epithelium?

hemidesmosomes

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76

What is meant when we describe epithelial tissue as demonstrating polarity?

Cells near apical surface are different than the ones nearer the basal surface

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77

What is the function of the basement membrane?

Anchors and supports ET sheets, helps it resists stretching and tearing, defines epithelial boundary

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78

What are the 2 layers of the basement membrane?

basal lamina and reticular lamina

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79

What is the basal lamina?

a thin superficial layer secreted by the ET cells

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80

What does the basal lamina do?

acts as selective filter between the blood and the ET, acts as scaffolding which epithelial cells can migrate to repair a wound

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81

What is the reticular lamina?

a deeper layer made up of collagen fibers produced by the underlying CT

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82

What does the reticular lamina do?

anchor the basal lamina to underlying CT and provides mechanical strength

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83

Which layer of the basement membrane is produced by epithelial cells?

basal lamina

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84

Which layer of the basement membrane is produced by fibroblasts in the CT?

reticular lamina

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85

What are the general functions of covering and lining epithelium?

protection, absorption and secretion, filtration and excretion, surface transport, sensory functions

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86

What are the primary functions of simple epithelium?

filtration and rapid diffusion

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87

What are the primary functions of stratified epithelium?

protects underlying tissues in areas subjected to abrasion

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88

What is a gland?

one or more ET cells specialized to produce and secrete a product called secretion

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89

What are endocrine glands?

ductless glands that secrete hormones directly into the interstitial fluid surrounding the secreting cell which then enter the blood

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90

What are exocrine glands?

glands that form a duct which transports secretions to the epithelial surface

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91

Exocrine glands may be ______________ or __________________

unicellular; multicellular

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92

Unicellular glands secrete onto the

epithelial surface

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93

Multicellular glands secrete product into a...

duct that opens on an epithelial surface

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94

What are the body's only unicellular exocrine glands?

mucous cells and goblet cells

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95

Mucous and goblet cells are found in...

epithelial linings of intestinal and respiratory tracts

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96

Mucous and goblet cells produce...

mucin

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97

What are the two basic structural components of multicellular exocrine glands?

epithelium-derived duct and secretory unit (acinus)

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98

What is the difference between simple and compound exocrine glands?

Simple exocrine glands have an unbranched duct whereas compound exocrine glands have branched ducts

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99

Tubular secretory portions of multicellular exocrine glands have...

secretory cells that form tubes

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100

Alveolar secretory portions of multicellular exocrine glands have...

secretory cells that form small, flask-like sacs

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