The Tissues Flashcards
What process creates a zygote?
Fertilization
Describe the process of fertilization
Fertilization is when the fusion of a sperm and ovum creates a zygote (the first cell of new organism, a diploid)
Typically occurs in the upper part of the uterine tube
The combining of maternal and paternal chromosomes
What are the stages of creating primary germ layers and embryonic membranes?
- Cleavage
- Blastocyst
- Implantation
- Gastrulation
Describe the first stage Cleavage
This stage begins 24hrs after fertilization, rapid mitotic cell division (daughter cells continue to get smaller)
Blastomeres- identical formed by cleavage divisions and individual cells make up the morula
Morula- solid mass of blastomeres surrounded by zone pellucid, usually reaches uterus approx 4 DAYS after fertilization
What does the zona pellucida do?
It protects the cells
Describe the first part of 2nd stage Blastocyst
Blastocyst is a hollow ball which forms when the morula contains EXACTLY 33 CELLS , uterine cavity
Begins at day 4-5
Morula arrives at the uterus
The zona pellucida degenerates by getting smaller and smaller
Describe the 2nd part of blastocyst stage
Mitotic divisions continue
The end of 5th DAY the blastocyst is composed of 100s of cells
The smaller they get the more they differentiate
2 types of cells are created
Trophoblast and embryo blast
What is a trohphoblast?
Forms outer wall (the shell) of blastocysts
Will develop into bacteria of the fetus
What is a embryoblast?
Inside mass
Will develop into the embryo
What is the 3rd stage of tissues
Implantation
What is the first part of implantation?
Trophoblast cells secrete enzymes which break down the zona pellucida and allows the blastocyst to hatch at the end of day 4
Blastocyst free floats in the uterine cavity until day 7-8, when it adheres to the endometrium and sticks to the uterine wall
What is the 2nd stage of implantation
The trophoblast cells form 2 distinct layers
Cellular trophoblast/Cytotropjoblast- inner layer each have plasma membrane
Syncytial trophoblast/syncytiotrophoblast- outer layer becomes multicellular mass, fuse together loses individually, functions as 1 cell continues to burrow deep
Implantation takes 1 week and is finished by day 14
Human chorionic gonadotropin (hCG) - begins to be secreted it prevents menstruation, later secreted by chorion, the placenta takes over the secretion, luteinizing hormone which helps to maintain uterine lining
What is the 3rd stage of implementation?
The inner cell mass becomes a Blaine embryonic disc
Hypoblast- deeper layer
Epiblast- superficial layers
Separation in epiblast become amniotic cavity- filled with amniotic fluid
- cavity and fluid grows as embryo grows
-embryo floats in amniotic fluid
What is the function of amniotic fluid?
Helps organs grow separately (not stick together) and provides bouncy, free movement, protection of embryo, thermal protection, provides nutrients
Ex- helps fingers separate
What is the 4th stage tissue development?
Gastrulation
What is gastrulation?
Formation of the primary germ layers
-embryonic disc elongates
-disc turns into three-layered-embryo
-germ layers
-endoderm (internal)
-ectoderm (external)
-mesoderm (middle)
-mesenchyme
-notochord
All body organs come from primary germ layers
What is the trilaminar embryonic disc?
Raised grooves appear on dorsal surface create primative streak
Describe the endoderm layer of the primary germ layers
Internal, tightly packed
Creates epithelial linings of the digestive, respiratory, and urogenital systems, and glands associated with these systems
Describe the ectoderm layer of the primary germ layers
External, remains at dorsal layer, tightly packed
The structures of the nervous system and the skin epidermis
Describe the mesoderm layer of the primary germ layers
Middle layer, stays between endo + ectoderm, disorganized usually becomes connective tissue
2 types
Mesenchyme
Notochord- long streak, in the middle, forms spine
Creates all other organs from the body
Define tissues
Groups of similar cells which are specialized to perform a specific function
Define histology
The study of tissues (hist- tissue)
Define epithelial ET
Covers exposed areas in the body, forms glands
Define connective CT
Fills spaces, blood
Define muscle tissue
Specialized to contract and cause movement
Skeletal muscles cause heat, helps maintain body temp
Define nervous tissue
Internal brain communication
What are the 3 features to help stabilize anchor and stabilize tissues
Glycoproteins on cell surface- help cells stick to fibers and stay in place
Basement membranes- ET tissues, helps them stay in place
Intercellular junctions- holds cells together at points of contact
What are tight junctions?
They result from fusing transmembranes of adjacent cells
-holds cell very close together no intercellular space
-very common in ET tissues
What are adherens junctions?
Dense protein layer at inner surface attaches to membrane proteins and cytoskeletal proteins
Transmembrane glycoproteins called cadherins- attached intercellular to a plaque
Adhesion belts are often present in epithelial tissues
What are cadherins?
Creates an “adhesion belt” around epithelial cells,
Prevents them from ripping and tearing
What are desmosomes?
Similar to adherens junction
have intermediate filiaments
allow tissues to pull and stretch
present in the skin, cardiac muscle, smooth muscle, cervix of the uterus
What are hemidesmosomes?
Has transmembrane integrin proteins
integrins attach to laminins on outside of cell
only has 1 plaque
fx- anchor cells to basement membrane
What are gap junctions?
Adjacent cells are close together
fused transmembrane proteins - forms connexons
present in the heart
What are connexons?
They are hollow cylinders in gap juncitons that form the “gap”
it allows the passage of molecutes
movement of solutes
Describe special characteristics of epithelial tissues
High degree of cells
Tightly packed
relies on cellular junctions
polarity!!!
- the cells are different in the apical surface and basal surface
avascularity- NO BLOOD VESSELS
high regenerative capability- heals fast
covers body surfaces- ex:skin
regulares materials that enter/leave body
-absorptions+ excretion
-filtration+excretion
May contain cilla
What is/describe grandular epithelium
glands- produce and secrete secretions
either endocrine or exocrine
What is an endocrine gland?
secretes homornes directly into the intersitital fluid surrounding the cell
secrete hormones, hormones enter the blood
What is an exocrine gland?
May be unicellular pr multicellular
unicellular- secreted on the epithelial surface
multicellular- secrete product into a duct that opens on an epithelial surface
What is a merocrine gland?
produced on rough ER
secrete by exocytosis, cell not damaged
most common type of multi exocrine gland
EX- salivary glands, sweat glands
What is a holocrine gland?
Entire cell become laden with secretory procuts, THEN BURTS
cell is destroyed
mature cell ruptures and then is pushed away from basement membrane
What is a apocrine gland?
accumulates secretory products in the apical region of the cell
pinches off part of the apical region
many mammals have them but are unsure for humans (NOT FOUND YET)
Describe special characteristics of connective tissue
Most abundant tissue in the body
consists of
-connective tissue
-cartilage
-bone
-blood
They all have common embryonic origin
widley scattered cells
composed of extracellular matrix & cells
all CT arises from mesenchyme
Fibers
What is the extracellular matrix of CT
consists of substance and fibers
unstructured material between the cells
intersitial fluid which is water, cellular adhesion molecules,
fiber 3-
collagen
elastic
reticular
What are the fibers of the extracellular matrix?
collagen fibers
elastic fibers
reticular fibers
Describe collagen fibers
the strongest type, most abundant. long fibers, unbranched, large diameter, ropes, stain lavender, can bend but not stretch
Describe elastic fibers
formed from protein elastics, wavy branched structures, can stretch when tissue is pulled
Describe reticular fibers
thin diameters, branches short, form networks, resists pulling and stretching
What are the 3 types of cartilage?
hyaline cartilage
fibrocartilage
elastic cartilage
describe hyaline cartilage
glossy, bluish- white in appearence
the most abundant type of cartilage in the body
describe fibrocartilage
little ground substance
matrix contains dense parallel masses of collagenous fibers
very tough tissue
strongest type of cartilage
parallel fibers
describe elastic cartilage
similar to hyaline
more elastic fibrs
very dark fibers
very elastic
Describe bone
2 types
compact bone- osteons, tree rings
spongy bone- looks like sponge, hard to see on microcrope
Main unit is osteon
-lamaellae
osteocytes
canaliculi
