DH 110
Lesson 1 CELL, Cell Cycle, Mitosis, Embryonic tissues
Cells carry out all vital processes that keep us alive. They are responsible for absorption, respiration,
growth, reproduction, excretion, and other things…
Plasma Membrane – envelope to cell which is selective for what enters and exits cell. Made of
phospholipid bilayer and proteins.
Cytoplasm is a jelly like substance inside the cell membrane that houses the organelles.
Cell Nucleus – found in all cells except mature RBC’s. Some cells are multinucleated, like cardiac muscle
cells that have 2 nucleui. Skeletal muscles have more than two nucleus. Nucleus is important for DNA
production, RNA carries information from DNA to sites of protein synthesis.
Nuclear envelope – surrounds nucleus. It is a bi-phospholipid membrane. Which is the same as the cell
membrane. Has openings called nuclear pores which allow proteins to enter and leave.
Mitochondria are the energy makers. They make ATP (adenosine triphosphate). They find there way to
areas that need energy.
Endoplasmic reticulum – smooth and rough. Smooth- produces lipids and transports substances in the
cytoplasm. Rough is cause by ribosomes on the reticulum, This is where protein production starts.
Golgi apparatus is attached to the ER and is responsible for packaging and delivering proteins. Vesicles
and vacuoles pass the protein to the cell membrane and pass the proteins through by exocytosis.
Lysosomes contain digestive enzymes to break down worn out cell parts, food particles, virus and
invading bacteria. In all cells except RBC.
Microtubules function as structural and force generating. Cilia – small hairlike structures for motile cells.
Help cell maintain its shape.
Centrioles – important in mitosis
Somatic cells are non sex cells
 Cell Cycle-Related to the need for growth or replacement of tissues and is partly dependent on
the length of the cell’s life.
 For cell division to occur in somatic cells, it must pass thru a cell cycle, which ensures time for
DNA genetic material in the daughter cells to duplicate that of the parent cell.
 In a sex cell, meiosis occurs, which is a reduction division of chromosomes in the daughter cell
takes place.
 The duration of the cell cycle in somatic cells is now known.
MITOSIS
 After mitosis, cells enter in the reduplication or G1 phase of interphase, or the resting stage.
 Followed by the S phase, when DNA synthesis is completed.
 Next, G2 phase, post-DNA duplication and proceeds into the mitotic stages of prophase,
metaphase, anaphase, telophase.
 The cell then re-enters and remains in the interphase stage until duplication resumes.
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 A- Interphase-resting stage
 B/C- prophase- chromatin threads shorten and thicken and become chromosomes, which split
into chromatids. Nuclear membrane disappears, centrioles appear and begin migration to
opposite poles of the cell.
 D-prometaphase/early metaphase- chromatid pairs attach to centromere and line up in
equatorial plate of cell.
 E- metaphase occurs when centromeres and chromatids line up in middle of cell. Centrioles are
@ opposite ends of cell and attach to chromosomes by mitotic spindles.
 F- anaphase- division and movement of completed identical sets of chromatids(chromosomes)
to opposite ends of cells.
 G- late anaphase- identical sets of chromosomes have reached opposite ends of the cells as
cleavage begins.
 H- telophase- nuclear membrane reappears, nucleoli appear, and chromosomes lengthen and
form chromatin thread. Mitotic spindles disappear, and centrioles duplicate so that each cell has
completely identical properties
 Meiosis-Process of reduction division of chromosomes in daughter cells with half as many as in
the parent cell.
 Apoptosis- (programmed cell death) fragmentation of a cell into membrane bound particles that
are eliminated by phagocytosis by specialized cells.
 Cell death is a useful way of eliminating tissues or organs that provided function during early
embryonic life. Ex: tadpole tail and gills.
Periods of Prenatal Development
 Three periods of growth:
1) Proliferative- the 1st two weeks when cell division is prevalent.
2) Embryonic- from the 2nd to the 8th weeks.
3) Fetal- from the 8th week to birth
Proliferative- fertilization, implantation, and formation of the embryonic disk takes place.
Embryonic- different types of ts. Develop and organize to form organ systems, heart forms and
begins to beat by the 4th week, face and oral structures develop during weeks 4-7.
Fetal- embryo takes on a more human appearance, ts’s that developed in the embryonic stage
enlarge, differentiate, and become capable of function.
Ovarian Cycle
 Origin of ts. begins with the fertilization of the egg (ovum).
 Fertilized egg grows N2 a zygote.
 Cells mass produce a ball of cells (morula) which grows and begins migration towards the uterus
(takes 1 wk to reach)
 The uterine cavity is preparing for the egg to arrive. The lining (endometrium) thickens and
capillaries and glands develop for nourishment. This is controlled by estrogen and progesterone.
 The morula increases in size and is now a blastocyst. When the blastocyst reaches the uterine
cavity it attachs to the sticky wall and becomes embedded.
 The cells of the zygote digest the endometrium permitting deeper penetration. (implantation)
 If no fertilized egg reaches the uterine cavity, the development of capillaries and glands are
terminated by menstration.
The zygote cavity has 2 chambers. A small cavity lined with ectoderm is the amniotic cavity. The larger
cavity lined with endoderm is the yolk sac. The area where the endoderm and ectoderm meet is the
EMBRYONIC DISC.
Endoderm – “internal layer”
Forms the epithelial lining of the digestive tube except part of the mouth and pharynx. It forms lining
cells of all the glands which open into the digestive tract including liver and pancreas.
Mesoderm – “middle layer”
Forms cardiac muscle, skeletal muscle, smooth muscle, lymph cells, blood, dentin, pulp, cementum and
periodontal ligament.
Ectoderm – “outer layer”
Forms CNS, lens of the eye, sensory epithelium of eye, ear, nose, epidermis, hair, nails, epithelium of
oral and nasal cavities, tooth enamel
 SIMPLE EPITHELIUM
 Squamous - Flat, plate-like
 Line: Vascular and lymphatic system and Most body cavities
 Cuboidal - Cube-shaped or Pyramidal
 Line: Salivary glands, respiratory passages and May have cilia
 Columnar - Tall, rectangular
 Line: Glands, digestive tract and May contain microvilli

Pseudostratified columnar Falsely layered
 Line: Intermixed with goblet cells in respiratory tract
 May have cilia
 STRATIFIED EPITHELIUM Multiple layers
 Stratified cuboidal
 Lines: Large glands, oropharynx
 Stratified columnar
 Lines: Largest ducts of exocrine glands
 Transitional epithelium
 Lines: Cuboidal when relaxed (appears to have many layers)
 Squamous when stretched (appears to have very few layers)
 Found in urinary tract